Protein Comprising a Collagen Domain of CCBE1 and Uses Thereof

Abstract

The invention relates among others to a protein comprising a fragment of 30-240 amino acids of Collagen and calcium-binding EGF domain-containing protein 1 (CCBE1) having 0-10 amino acid substitutions with respect to the amino acid sequence of SEQ ID NO: 1, wherein said fragment comprises at least a collagen domain of CCBE1, or a variant thereof comprising 1, 2 or 3 amino acid substitutions. The invention further describes means and methods for the treatment of individuals with the protein or protein binding thereto.

Claims

1. A protein comprising a fragment of 30-240 amino acids of collagen and calcium-binding EGF domain-containing protein 1 (CCBE1) having 0-10 amino acid substitutions with respect to an amino acid sequence of SEQ ID NO: 1, wherein said fragment comprises at least a collagen domain of CCBE1, or a variant thereof comprising 1, 2 or 3 amino acid substitutions.

2. The protein of claim 1, wherein said collagen domain comprises amino acid 300-333 as defined in SEQ ID:NO 1 or a variant thereof comprising 1, 2 or 3 amino acid substitutions, or an equivalent of said domain in an ortholog of human CCBE1, or a variant thereof comprising 1, 2 or 3 amino acid substitutions.

3. The protein of claim 1, wherein said fragment comprises two collagen domains of CCBE1.

4. The protein of claim 3, wherein said collagen domains comprise amino acid 245-290 as defined in SEQ ID:NO 1 or a variant thereof comprising 1, 2 or 3 amino acid substitutions; and amino acid 300-333 as defined in SEQ ID:NO 1 or a variant thereof comprising 1, 2 or 3 amino acid substitutions, or an equivalent thereof in an ortholog of human CCBE1 or a variant of said equivalent comprising 1, 2 or 3 amino acid substitutions.

5. The protein of claim 1, comprising amino acids 245-333 of human CCBE1 as defined in SEQ ID:NO 1 or a variant thereof comprising 1, 2, 3 or 4 amino acid substitutions, or an equivalent thereof in an ortholog of human CCBE1 or a variant of said equivalent comprising 1, 2, 3 or 4 amino acid substitutions.

6. A nucleic acid molecule encoding the protein of claim 1.

7. A cell or non-human animal comprising the nucleic acid molecule of claim 6.

8. A binding protein that binds the collagen domain of the protein of claim 1.

9. The binding protein of claim 8 wherein the binding protein is an antibody or functional part, derivative or analogue thereof.

10. A method of producing lymphatic channels, increasing lymphangiogenesis and/or inducing a migration of lymphangioblasts in an animal, comprising administrating an effective amount of the protein of claim 1 to said animal.

11. A method of inhibiting a formation of lymphatic channels, lymphangiogenesis and/or a migration of lymphangioblasts in an animal comprising administering an effective amount of the binding protein of claim 8 to said animal.

12. A method for treating cancer in an animal wherein the protein of claim 1 is administered to the animal and produces lymphatic channels, increases lymphangiogenesis and/or induces a migration of lymphangioblasts in the animal.

13. A method for treating cancer in an animal wherein the binding molecule of claim 8 is administered to the animal and inhibits a formation of lymphatic channels, lymphangiogenesis and/or a migration of lymphangioblasts in the animal.

14. The method of claim 12 wherein the animal is a human.

15. A method for manipulating a formation of lymphatic channels, lymphangiogenesis and/or a migration of lymphangioblasts in a cell culture capable thereof, comprising providing the cell culture with the protein of claim 1.

16. The method of claim 13 wherein the animal is a human.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0071] FIG. 1: CCBE1 variants lacking the EGF domains or the collagen repeat domains cannot substitute for wild type CCBE1 in vivo.

[0072] (A) Schematic representation of CCBE1 wild type and deletion mutants. CCBE1ΔEGF and CCBE1ΔCol lack the EGF and Ca-EGF domains or both collagen repeat domains, respectively. Depicted are the signal peptide (SP), EGF and Ca-EGF domains, collagen repeat A (ColA) and collagen repeat B (ColB). (B) Genetic targeting strategy for the generation of CCBE1ΔEGF mice. Homologous recombination event replaces exons 4 and 5 with an FLPe flanked neomycin resistance cassette followed by a LoxP flanked exon 4 and 5. FLPe mediated deletion of the neomycin resistance cassette and Cre mediated deletion of exon 4 and 5 leads to a transcript which is depleted of the EGF and Ca-EGF domains. (C) Genetic targeting strategy used for generating CCBE1ΔCol and CCBE1FL mice. Homologous recombination replaces exon 7 with a construct containing exon 7 to 11 with or without the collagen repeats, followed by a transcriptional stop and an FLPe flanked neomycin resistance cassette. The neomycin cassette was removed by crossing heterozygous mice to FLPe mice. (D) Edema formation in CCBE1ΔEGF, CCBE1ΔCol and CCBE1LacZ mice at E14.5. CCBE1FL knock-in mice were indistinguishable from wild type controls.

[0073] FIG. 2: CCBE1ΔCollagen mice lack all lymphatic structures, while lumenized lymphatic structures do develop in CCBE1ΔEGF fetuses.

[0074] (A) Skin stainings of blood and lymphatic vessels of E14.5 fetuses visualized by PECAM-1 and Lyve-1/Prox1 staining. CCBE1ΔCol fetuses phenocopy CCBE1LacZ mice with a complete lack of lymphatic vessels in the skin. CCBE1ΔEGF skins feature remnant lymphatic structures which are unable to form a branched lymphatic network. CCBE1FL knock-in mice do not show any overt differences to wild type control fetuses. (B) Lyve-1 stainings of transverse paraffin sections of E14.5 fetuses showing lumenized lymphatic structures in CCBE1ΔEGF fetuses, but not in CCBE1ΔCol or CCBE1 LacZ fetuses. Note that lymphatic structures in CCBE1ΔEGF fetuses are smaller than in wild type control fetuses. Lymphatic structures in CCBE1FL knock-in mice are indistinguishable from those in control fetuses. CV: Cardinal vein, DA: Dorsal Aorta, LV: Lymphatic vessel, LS: Lymphatic structure, pTD: primordial Thoracic duct

[0075] FIG. 3: Migration of specified LECs from the cardinal vein is completely impaired in CCBE1ΔCollagen or CCBE1LacZ embryos, while lymphatic structures form in CCBE1ΔEGF embryos.

[0076] (A) 3D projections of whole mount immunostainings of cleared E12.5 embryos for Prox1, PECAM-1 and Lyve-1 analyzed on a confocal microscope. CCBE1ΔCol and CCBE1LacZ embryos do not show any LECs outside the cardinal vein, while CCBE1ΔEGF embryos exhibit remnant lymphatic structures at the position of the pTD and PLLV. CCBE1FL knock-in embryos do not show any overt defects. CV: Cardinal vein, LS: Lymphatic structure, pTD: primordial thoracic duct, PLLV: peripheral longitudinal lymphatic vessel

[0077] FIG. 4: CCBE1 lacking the EGF domains or the first collagen domain, but not CCBE1 lacking the second collagen domain can increase the activity of VEGFC in vivo.

[0078] (A-G) Injection of ccbe1 mRNA into Tg(shh:vegfc) induced aberrant, ectopic turning of intersegmental arteries at 32 hpf. Confocal projections show representative images of control and injected embryos in a Tg(fli1a:EGFP) background. In this assay, the ccbe1fof mutant has nearly full activity, while ccbe1ΔEGF and ccbe1ΔcolA have reduced activity compared to wt ccbe1. Removal of both collagen domains (ccbe1Δcol) or only the second collagen domain (ccbe1ΔcolB) completely abolishes the effect of ccbe1. (H) Percentage of embryos showing wild type (no arterial sprouting), mild (aberrant ISAs spanning up to two somites) or severe (aberrant ISAs spanning more than two somites) arterial sprouting in Tg(shh:vegfc) embryos that are uninjected or were injected with wt ccbe1, ccbe1fof, ccbe1ΔEGF, ccbe1Δcol, ccbe1ΔcolA and ccbe1ΔcolB (n=101, 427, 149, 182, 93, 149, 188, respectively). Injection of ccbe1 mRNA into wild type embryos does not induce strong bilateral sprouting of ISA (FIG. 9).

[0079] FIG. 5: The second collagen domain of CCBE1 is essential for activation of proteolytic processing of VEGFC in vitro.

[0080] (A) Schematic representation of CCBE1 deletion mutants. CCBE1ΔEGF, CCBE1ΔCol, CCBE1ΔColA and CCBE1ΔColB lack the EGF domains, both collagen domains or collagen domain A or B, respectively. Amino acids 291 to 299 comprising amino acids between the two collagen domains and amino acids 92 to 294 including both EGF domains and the first collagen repeat are deleted in CCBE1Δ291-299 and CCBE1 ΔEGFΔColA, respectively. Depicted are the signal peptide (SP), EGF and Ca-EGF domains, collagen repeat A (ColA) and collagen repeat B (ColB). (B-E) Conditioned medium from HEK-293T cells transfected with indicated constructs was collected two days after transfection and analyzed by Western blotting using antibodies for VEGFC and CCBE1. Note that VEGFC antibodies are able to recognize both the intermediate 31 kDa form and the fully processed mature 21 kDa form of VEGFC. CCBE1 antibodies recognize an epitope in the C-terminus of the protein, allowing detection of all variants used in this study. (B) Wt CCBE1 as well as CCBE1ΔEGF increased the amount of fully processed 21 kD VEGFC in the supernatant of HEK-293T cells, while CCBE1ΔCol had no effect on the levels of mature VEGFC. (C) CCBE1ΔColA and CCBE1Δ291-299 are able to increase the amounts of fully processed VEGFC in equal amounts as wt CCBE1, while CCBE1ΔColB had no effect on mature VEGFC levels. (D) Wt CCBE1, CCBE1ΔEGF and CCBE1ΔEGFColA, but not CCBE1ΔCol enhance VEGFC processing. (E) Expression of ADAMTS3 increases VEGFC processing which is further enhanced by co-expression of wt CCBE1, CCBE1ΔEGFbut not by CCBE1ΔCol.

[0081] FIG. 6: Effect of HS patient mutations on the activity of CCBE1.

[0082] (A) Schematic illustration of the functional domains of CCBE1 with an overview of the described mutations. Illustrated are the Signal Peptide (SP), EGF domain (EGF), Calcium binding EGF domain (Ca-EGF), collagen repeat A (ColA), and collagen repeat B (ColB). (B) Injection of ccbe1-myc mRNA and Ccbe1-mycR150C into Tg(shh:vegfc) embryos leads to strong bilateral sprouting of ISA while ccbe1-myc G313R has nearly no effect on arterial sprouting. (C) Quantification of the percentage of embryos with wild type (no arterial sprouting), mild (aberrant ISAs spanning up to two somites) or severe (aberrant ISAs spanning more than two somites) arterial sprouting in Tg(shh:vegfc) embryos upon injection of ccbe1-myc, ccbe1-mycR150C or ccbe1-mycG327R mRNA. n=94, 178, 137, 113 for uninjected controls, ccbe1-myc, ccbe1-mycR158 and ccbe1-G327R, respectively. (D) VEGFC processing assays were performed as in FIG. 5 B-E. Wt CCBE1 and CCBE1 R158C stimulate processing of VEGFC, while CCBE1 G327R has only strongly reduced activity.

[0083] FIGS. 7A and 7B: Model for regulation of VEGFC by CCBE1

[0084] Schematic model of CCBE1 domains interacting with ECM components and the ADAMTS3 protease, respectively. The N-terminal part of CCBE1 binds to the ECM, thereby restricting the range of CCBE1 activity and (ultimately) determining the site of VEGFC processing. The collagen repeat domains activate ADAMTS3 and are crucial (especially the Col B domain) for the eventual processing step which produces fully mature VEGFC protein. The EGF domains are indispensable in vivo for creating local high-points of VEGFC production, while in vitro (possibly due to high expression levels of transfected CCBE1 variants) they are not required. The collagen repeat domains are essential in both settings. Thus, CCBE1 generates locations of high VEGFC activity which directs LECs via VEGFR3 signaling.

[0085] FIG. 8: CCBE1ΔEGF and CCBE1ΔCol cannot substitute for wild type CCBE1 in vivo.

[0086] (A) Sequencing of cDNA isolated from homozygous CCBE1ΔEGF embryos showing correct splicing from exon 3 to 6. (B) Edema formation in CCBE1ΔEGF/CCBE1ΔCol fetuses at E14.5.

[0087] FIG. 9: Rudimentary lymphatics develop in the skin of CCBE1ΔEGF, but not of CCBE1ΔCollagen fetuses.

[0088] Skin stainings of blood and lymphatic vessels visualized by PECAM-1 and Lyve-1/Prox1 staining in E16.5 embryos. CCBE1ΔCol fetuses phenocopy CCBE1LacZ mice with a complete lack of lymphatic vessels in the skin.CCBE1ΔEGF skins feature remnant lymphatic structures which are unable to form a branched lymphatic network. CCBE1FL knock-in mice do not show any overt differences to wild type control fetuses.

[0089] FIG. 10: CCBE1 lacking the EGF domains or the first collagen domain, but not CCBE1 lacking the second collagen domain can increase the activity of VEGFC in vivo.

[0090] Percentage of embryos showing wild type (no arterial sprouting), mild (aberrant ISAs spanning up to two somites) or severe (aberrant ISAs spanning more than two somites) arterial sprouting in Tg(shh:vegfc) and wild type embryos that are uninjected or were injected with the indicated ccbe1 variant mRNAs. Tg(shh:vegfc) embryos: n=101, 427, 149, 182, 93, 149, 188 for injection of wt ccbe1, ccbe1fof, ccbe1ΔEGF, ccbe1Δcol, ccbe1ΔcolA and ccbe1Δcol mRNA, respectively. Wt embryos: n=55, 117, 42, 53, 52, 69, 56 for injection of f wt ccbe1, ccbe1fof, ccbe1ΔEGF, ccbe1Δcol, ccbe1ΔcolA and ccbe1Δcol mRNA, respectively

[0091] FIG. 11: A D170E mutation in CCBE1 equivalent to the fof mutation in zebrafish does not affect CCBE1 function in vitro.

[0092] The VEGFC processing assay was performed as in FIG. 5 (B-E). CCBE1 D170E activates processing of VEGFC similar to wt CCBE1 and CCBE1ΔEGF, while CCBE1ΔCol had no effect on VEGFC processing.

EXAMPLES

[0093] Material and Methods

[0094] Mouse Lines:

[0095] Mouse lines were maintained at the Hubrecht Institute using standard husbandry conditions. Experiments were approved by the local Animal Experimentation Committee (DEC). Generation of CCBE1ΔEGF, CCBE1ΔCol and CCBE1FL mice is described herein below. All mouse lines were crossed at least 5 times to C57Bl6 mice before analysis.

[0096] Zebrafish Lines

[0097] The Tg(fli1a:EGFP) and Tg(shh:vegfc) were described previously.sup.10, 20.

[0098] mRNA Injection

[0099] ccbe1 mRNA was transcribed from a NotI-linearised template using SP6 RNA polymerase and the mMessage mMachine Kit (Ambion), and injected at 400 pg/embryo.

[0100] Whole Mount Staining of Murine Fetal Skin

[0101] Whole mount staining of dorsal skin preparations of fetuses from staged matings was performed as previously described.sup.21 using anti-PECAM1, anti-Lyve-1 and anti-Prox1 as primary antibodies. Images were acquired on a Leica SP8 confocal microscope.

[0102] Staining of Mouse Fetuses

[0103] Paraffin sections were dewaxed and rehydrated. After blocking of endogenous peroxidase in blocking buffer (0.040M citric acid, 0.121M disodium hydrogen phosphate, 0.030M sodium azide, 1.5% hydrogen peroxide) for 15 min at room temperature, epitope retrieval in citrate buffer (10 mM sodium citrate monohydrate, pH 6.0) and blocking in 2% BSA in PBS for 1 h, tissue sections were incubated over night at 4° C. with an anti-Lyve-1 antibody followed by incubation with the secondary antibody added (polymer HRP-labelled anti-mouse/rabbit, Envision) for 30 min at room temperature. Peroxidase was detected by DAB substrate using the SIGMAFAST DAB with Metal Enhancer Tablet Set according to manufacturer's instructions. Tissue sections were counterstained with Mayer's haematoxylin.

[0104] Whole Mount Staining and Optical Clearing of Mouse Embryos

[0105] Whole mount embryos were stained and cleared as described previously.sup.22 using anti-Prox1, anti-PECAM-1 and anti-Lyve-1 as primary antibodies. Cleared embryos were imaged on a Leica SP8 confocal microscope. 3D stacks were generated using Fiji (Image J).

[0106] VEGFC Processing In Vitro

[0107] VEGFC processing in vitro was performed as described a. Briefly, HEK293T cells were transfected with VEGC and/or CCBE1 cDNA using XtremeGene (Roche) according to manufacturer's instructions. Conditioned media were collected and mixed with Laemmli sample buffer. Western blotting analysis was performed using VEGFC (VEGFC isoform 103 antibody, antibodies-online) and CCBE1 (HPA041374, Sigma) antibodies.

[0108] Antibodies and Reagents:

[0109] The following antibodies were used: Anti-Lyve1 (#11-034, Angiobio), Anti-Lyve-1 (AF2125, R&D Systems), Anti-CD31 Mec13.3 (#550274, Pharmingen), anti-Prox1 (102-PA32, ReliaTech), anti-Prox1 (AF2727, R&D Systems), anti-VEGFC (isoform 103 antibody, antibodies-online), and anti-CCBE1 (HPA041374 Sigma). All Alexa-coupled antibodies were purchased from Invitrogen, HRP coupled antibodies were used from Dako.

[0110] Constructs:

[0111] Ccbe1 (wild type), ccbe1fof, ccbe1-myc, ccbe1-mycR150 and ccbe1myc-G313R cDNA clones have been described previously.sup.12, 18. Zebrafish ccbe1ΔEGF was generated by amplification of ccbe1 pCS2 followed by religation. Zebrafish ccbe1Δcol, ccbe1ΔcolA and ccbe ΔcolB were generated by site-directed mutagenesis using wt ccbe1 in PCS2 as template. Human CCBE1 was subcloned into the pBabe vector in Xho1-EcoR1 restriction sites. Mutant variants of CCBE1 for expression in human cells were generated by site directed mutagenesis. Primer sequences used for generation of deletion mutants and mutants containing the HS mutations are given in Table I.

TABLE-US-00001 TABLE I Construct Primer forward (5′-3′) Primer reverse (5′-3′) Zebrafish Ccbe1 ΔEGF ttctggaatacactgaccc gaaaaatcagacaacgtcatg Zebrafish ccbe1Δcol atgacgacaaattcattttcctttgacttcctgtta taacaggaagtcaaaggaaaatgaatttgtcgtcat Zebrafish ccbe1ΔcolA atgacgacaaattcattttcccctgacctgtcgcat atgcgacaggtcaggggaaaatgaatttgtcgtcat Zebrafish ccbe1ΔcolB ctgtcgcatatcaaacagtcctttgacttcctgtta taacaggaagtcaaaggactgtttgatatgcgacag Human CCBE1 ctcgagatggtgccgccgcctccg gaattcctatgggtagaagtctct Human CCBE1 D170E tacatccgggaagatgaagggaagacatgtacc ggtacatgtcttcccttcatcttcccggatgta Human CCBE1 ΔEGF atcccagaagattacgacaggggagacaaatatccc gggatatttgtctcccctgtcgtaatcttctgggat Human CCBE1 Δcol ctggcctcaaacacctactctttcgacttcctgcta tagcaggaagtcgaaagagtaggtgtttgaggccag Human CCBE1 ΔcolA ctggcctcaaacacctactctcctgatctgtcccac gtgggacagatcaggagagtaggtgtttgaggccag Human CCBE1 ΔcolB ctgtcccacattaagcaatctttcgacttcctgcta tagcaggaagtcgaaagattgcttaatgtgggacag Human CCBE1 4291-299 atgggacccatgggaccaggccggaggggccctgtg cacagggcccctccggcctggtcccatgggtcccat Human CCBE1 ΔEGFΔcolA ccagaagattacgactcccacattaagcaa ttgcttaatgtgggagtcgtaatcttctgg Human CCBE1 R158C accttgggcagctactgctgcgagtgccgggaa ttcccggcactcgcagcagtagctgcccaaggt Human CCBE1 G327R gcgcctgggcccagaaggtctccaggaccccct agggggtcctggagaccttctgggcccaggcgc

[0112] Targeting Strategy for the Generation of CCBE1ΔEGF and CCBE1ΔCol Mice:

[0113] CCBE1ΔEGF mice were generated by homologous recombination of mouse SV129 ES cells using a targeting vector that contains a 4.2 kb long arm of homology 5′ of exon 4, an FLPe flanked neomycin resistance cassette, a LoxP flanked exon 4 to 5 and a 2 kb short arm of homology 3′ of exon 5. Neomycin-resistant clones were screened by Southern blot analysis. The Neomycin resistance cassettes were removed by crossing to FLPe mice, and exon 4 and 5 of CCBE1 were deleted by crossing floxed mice to PGK-Cre mice. For the generation of CCBE1ΔCol mice, mouse SV129 ES cells were transfected using a targeting vector comprising a 4.5 kb arm of homology 5′ of exon 7, the cDNA of exon 7 to 11 lacking bp encoding aa 248 to 337 followed by a Flag-HA tag, a transcriptional stop, an FLPe flanked neomycin resistance cassette followed by a single LoxP site and a 4.2 kb arm of homology 3′ of exon 7. CCBE1FL mice were generated analogous to CCBE1ΔCol mice encoding the complete cDNA of exon 7 to 11. The Neomycin resistance cassette was removed by crossing to FLPe mice.

[0114] Results

[0115] CCBE1 Variants Lacking Either the EGF or the Collagen Repeat Domains Cannot Substitute for Wild Type CCBE1 In Vivo.

[0116] To investigate the relevance of the different domains of CCBE1 in vivo, we generated knock-in mice expressing different deletion mutants of CCBE1, lacking either the EGF and Ca-EGF domains (CCBE1ΔEGF mice) or lacking both collagen repeat domains (CCBE1ΔCol mice) (FIG. 1 A). In order to remove the EGF domains in CCBE1, we generated mice with floxed exons 4 and 5 (FIG. 1 B). Cre-mediated recombination led to an in-frame deletion of exon 4 and 5 removing both the EGF domains. Correct splicing from exon 3 to 6 was verified by sequencing of cDNA from homozygous CCBE1ΔEGF embryos (FIG. 8). For CCBE1ΔCol mice, removal of the two collagen repeat domains was achieved by replacement of exon 7 of CCBE1 with the cDNA of exon 7 to 11 lacking amino acids 248 to 337 followed by a transcriptional stop (FIG. 1 C). Analogous to this knock-in, a CCBE1 full length (FL) knock-in mouse was generated as a control in which exon 7 is replaced with the cDNA of exon 7 to 11 including the collagen domains followed by a transcriptional stop. Homozygous CCBE1FL control knock-in mice were viable and fertile and did not show any overt morphological defects (FIG. 1D). Homozygous fetuses expressing CCBE1ΔEGF or CCBE1ΔCol present with severe edema at E14.5 and die in utero, thus phenocopying the CCBE1 full knock-out in which a LacZ cassette was placed into the CCBE1 locus (CCBE1LacZ)==2 (FIG. 1D). Heterozygous animals for both CCBE1ΔEGF and CCBE1ΔCol mutants were viable and fertile and did not show any overt edemic phenotype, but fetuses compound heterozygous for CCBE1ΔEGF and CCBE1ΔCol show the same phenotype as mice homozygous for the two alleles (FIG. 8).

[0117] Thus, mutant CCBE1 proteins lacking either the EGF domains or the collagen repeat domains cannot substitute for wild type CCBE1 in vivo.

[0118] CCBE1ΔCollagen Mice Lack all Lymphatic Structures, but Lumenized Lymphatic Structures Develop in CCBE1ΔEGF Fetuses.

[0119] Previously, we have shown that CCBE1 knock-out mice lack all lymphatic vessels, while the patterning of blood vessels is not affected.sup.15. In order to analyze lymphatic and blood vessel development in mice expressing CCBE1 lacking either the EGF domains or the collagen repeat domains, we performed skin stainings of mutant fetuses at E14.5 to E16.5 (FIG. 2A, FIG. 9) using Lyve1 and Prox1 as lymphatic markers and the pan-endothelial marker CD31 to visualize blood vessels. We observed no abnormalities in blood vessels in any of the mice. Moreover CCBE1FL knock-in mice do not show obvious differences in lymphatic vessel development in the skin compared to wild type animals. Homozygous CCBE1ΔCol fetuses phenocopy CCBE1LacZ mice lacking all lymphatic vessels in the skin. Interestingly, however, CCBE1ΔEGF mice do exhibit some lymphatic structures in the skin. Like lymphatic vessels in wild type control fetuses, these structures sprouted into the direction of the dorsal midline at E14.5, but they failed to develop into a contiguous, branched plexus compared to wt control fetuses at both time points analyzed. At E16.5, patches of lymphatic endothelial cells had aggregated and formed large circular structures. Next we performed Lyve-1 stainings of paraffin sections of E14.5 fetuses (FIG. 2B) to investigate lymphatic development at other positions close to the CV and to assess whether these vessels are lumenized. While the pTD and other large lymphatic vessels in other areas such as the skin could be readily identified in wild type control and in CCBE1FL knock-in fetuses, lymphatic vessels were undetectable in CCBE1ΔCol or CCBE1LacZ mice. Analogous to the whole mount stainings, lymphatic vessels were found in the skin of E14.5 CCBE1ΔEGF fetuses. Moreover, lymphatic structures were also identified at the position of the pTD; however, these structures were smaller than in wild type control animals.

[0120] Collectively, these results reveal that while both the collagen domains and the EGF domains are necessary for lymphatic development, a CCBE1ΔEGF mutant does retain partial functionality in vivo.

[0121] Specified LECs Migrate from the Cardinal Vein in CCBE1ΔEGF Embryos, but not in CCBE1ΔCollagen or CCBE1LacZ Embryos.

[0122] In order to analyze lymphatic development in more detail and at an earlier stage, we visualized the formation of the first lymphatic structures by whole mount staining and optical clearing of E12.5 embryos. Recently, it had been shown that specified LECs leave the CV as streaks of cells to form the first two large, lumenized lymphatics vessels, the PLLV and the pTD. In CCBE1LacZ knock-out embryos as well as in CCBE1ΔCol embryos, Prox1+ or Lyve1+ LECs are unable to leave the CV and were not detected outside of the CV. In CCBE1ΔEGF mice however, some Prox1+ cells were able to leave the cardinal vein but only formed discontinuous lymphatic structures at the positions where the pTD and PLLV are normally located (FIG. 3).

[0123] Thus, the CCBE1ΔCol mutant has no activity in vivo. The CCBE1ΔEGF mutant is able to induce migration of lymphatic progenitor cells out of the CV at early time points of lymphatic development, although it cannot induce the formation of the main lymphatic structures, the PLLV and pTD.

[0124] The Second Collagen Domain of Ccbe1 is Essential for Enhancing Vegfc Signaling in Zebrafish.

[0125] To confirm and extend our findings in an independent system, we employed an assay that assesses Vegfc signaling in zebrafish I-U. Previously we have shown that Tg(shh:regfc;shh:ccbe1) zebrafish, expressing both regfc and ccbe1 as independent transgenes in the floorplate from the shh promoter, exhibit aberrant ectopic turning of arteries at 32 hpf.sup.10, while single transgenic zebrafish do not. This phenotype can be attributed to high Vegfc/Vegfr3 signaling in arteries.sup.2. Injection of ccbe1 mRNA in Tg (shh:regfc) embryos that only express regfc from the shh promoter also efficiently induced strong arterial sprouting (FIG. 4B,H), while injection of ccbe1 mRNA into wt embryos had no effect (FIG. 10). First, we tested the activity of ccbe1fof in this assay. Ccbe1fof harbors a mutation in the EGF domain (D162E), leading to a loss of lymphatic development in zebrafish mutants.sup.12. Unexpectedly, ccbe1fof mRNA has levels of activation that are indiscernible from wt ccbe1 (FIG. 4B, C, H). Interestingly and in accordance to the mouse data, ccbe1ΔEGF was still able to induce mis-turning of arteries, albeit to a lower degree than wt ccbe1 (FIG. 4D, H). In contrast, ccbe1ΔCol mRNA injection did not induce ectopic arterial turning (FIG. 4E,H). To further narrow down which part of the collagen domains was required for its function we tested mutant forms of ccbe1 in which either the first or the second collagen domain was removed. Interestingly, we found that deletion of the first collagen domain, ccbe1ΔColA, only led to a partial loss of function in the ability to induce ectopic turning whereas loss of the second collagen domain, ccbe1ΔColB led to a complete loss of function (FIG. 4 F-H).

[0126] Thus, the EGF and Ca-EGF domain as well as the first collagen domain are required for full function of the Ccbe1 protein, however, only removal of the second collagen domain fully renders the Ccbe1 protein dysfunctional in regulating Vegfc signaling in zebrafish. These data are in alignment with the above-described mouse mutant analysis.

[0127] The Second Collagen Domain of CCBE1 is Required for Enhancement of Proteolytic Processing of VEGFC by CCBE1 In Vitro.

[0128] CCBE1 has recently been shown to enhance proteolytic processing of VEGFC, which leads to an increase in bioavailability of the mature 21 KDa form of VEGFC.sup.10, 17. To assess how the various functional domains affect the ability of CCBE1 to increase mature VEGFC levels we co-expressed human VEGFC together with wt or various mutant forms of CCBE1 in HEK293T cells. Conditioned media containing secreted VEGFC and CCBE1 were analyzed by Western blotting. As reported before, CCBE1 clearly stimulated the proteolytic processing of VEGFC as is apparent from an increased amount of the 21 KDa form of VEGFC. Surprisingly, we found that the EGF domains are not required for CCBE1 function in VEGFC processing in vitro as co-expression of CCBE1ΔEGF led to an increase in mature VEGFC comparable to that of wt CCBE1 (FIG. 5B). Moreover, CCBE1D170E, which harbors a point mutation that is equivalent to the fof mutation in zebrafish, was also able to enhance processing of VEGFC in this assay (FIG. 11), further corroborating that perturbation of the EGF domain does not impair CCBE1 mediated processing of VEGFC in vitro.

[0129] In contrast, the mutant form of CCBE1 that lacks the collagen domains (CCBE1ΔCol) lost the ability to increase VEGFC processing. As the zebrafish experiments indicated that the two collagen domains are not equally important for CCBE1 function in mediating VEGFC signaling in vivo, we tested whether these domains would also have differential effects on VEGFC processing in vitro. Strikingly, deletion of the first collagen domain (CCBE1ΔColA) was dispensable for activation of VEGFC processing in this assay, however, deletion of the second collagen domain (CCBE1ΔColB) inhibited activation of VEGFC processing by CCBE1 (FIG. 5C). To exclude a role for the amino acids that lie between the two collagen domains we deleted amino acids 291-299 and showed that this alteration does not affect CCBE1 function. Moreover, even deletion of amino acids 92 to 294, which deletes all parts of the protein from the EGF domains to the first collagen domain, did not have an overt effect on CCBE1 function in this assay (FIG. 5D).

[0130] Since CCBE1 has been suggested to mediate processing of VEGFC via the ADAMTS3 protease.sup.17, we also tested if ADAMTS3 cooperates with mutant forms of CCBE1. We generated a stable cell line expressing VEGFC and subsequently co-expressed ADAMTS3 and CCBE1. We found that ADAMTS3 on its own induced a mild increase of proteolytic processing which was further increased by co-expression of CCBE1 and CCBE1ΔEGF. This induced a strong loss of the 31 kD form and a concomitant increase of 21 kD form of VEGFC which was never seen in the absence of ADAMTS3. In agreement with our other findings, lack of the collagen domains abrogates the synergism between CCBE1 and ADAMTS3 (FIG. 5E).

[0131] Taken together, these data suggest that the collagen domains are indispensable for processing of VEGFC by CCBE1, however, all other functional domains tested are dispensable for its activity in vitro.

[0132] Only a Hennekam Mutation in the Collagen Domain, but not in the Ca-EGF Domain Fully Impairs CCBE1 Function.

[0133] CCBE1 mutations have been shown to be causative for HS, a congenital autosomal recessive disease, which is characterized by lymphangiectasia, generalized lymphoedema and mental retardation.sup.18. Most of the mutations inducing HS have been identified affecting the N-terminal part of the protein, containing a cysteine rich sequence N-terminal of the EGF domains and the EGF and Ca-EGF domains (FIG. 6A). Only two mutations have been found within the collagen domains, with one patient harboring a mutation in the second collagen domain, G327R. To interrogate the effect of the mutations responsible for the HS phenotype on the functionality of CCBE1, we tested two constructs that bear mutations found in HS patients in our assays. One mutation, R158C, is located within the Ca-EGF domain and one mutation, G327R, within the second collagen repeat. First, we tested the functionality of these two mutants in vivo by injecting zebrafish ccbe1 mRNAs that bear the corresponding mutations into Tg(shh:vegfc) embryos. Whereas the zebrafish R150C mutation, equivalent to human R158C and located in the Ca-EGF domain, only marginally lowered activity compared to wt ccbe1 in this assay, the mutation in the collagen domain, G313R in zebrafish, completely abolished Ccbe1 function (FIG. 6B,C). Moreover, in an in vitro processing assay using human CCBE1 the R158C mutation in the Ca-EGF domain did not affect functionality of CCBE1 compared to the wild type molecule, while the G327R mutation in the second collagen domain led to a strong loss of VEGFC activation (FIG. 6D).

[0134] Discussion

[0135] CCBE1 is one of the very few genes that are indispensable for embryonic lymphatic development.sup.1. It has been shown that CCBE1 is a crucial regulator of VEGFC activation via the protease ADAMTS3. However, which domains of CCBE1 are necessary to exert its function is not known. Here we have conducted a functional domain analysis, based on different in vitro and in vivo systems, to gain comprehensive insight into the requirement of the different conserved protein domains for CCBE1 activity.

[0136] Several lines of evidence have stressed the importance of the EGF domains in the past. First, the majority of mutations in CCBE1 in HS patients have been found within, or in close proximity to the EGF domains. Second, in the original screens that identified zebrafish ccbe1 as an essential gene for lymphatic development, several alleles were identified in which the causative mutation was found to be located in the EGF or Ca-EGF domain.sup.12, unpublished data. To gain more insight into the function of the EGF and Ca-EGF domains, we generated knock-in mice expressing a CCBE1 variant lacking these domains. Surprisingly, unlike the full CCBE1 knock-out fetuses which lack all lymphatic structures, CCBE1ΔEGF fetuses do develop rudimentary, lumenized lymphatic vessels in the skin and at the position of the pTD and PLLV. In the skin, these lumenized larger structures sprouted into the same direction to the dorsal midline as lymphatic vessels in wt fetuses. They did, however, fail to form a properly branched lymphatic network. In CCBE1ΔEGF embryos, remnant, fragmented lymphatic structures were located at the position of the pTD and PLLV indicating that specified LECs do migrate out of the cardinal vein roof to the same location as LECs in wild type control embryos. In accordance with this, a Ccbe1ΔEGF mutant was partially functional in zebrafish, were the injection of ccbe1ΔEGF can still exert aberrant arterial sprouting in the Tg(shh:vegfc) zebrafish. Although ccbe1fof could increase Vegfc signaling in arteries to the same extent as wt ccbe1, it cannot substitute for wt ccbe1 in zebrafish since, in contrast to wt ccbe1 mRNA, it is not able to rescue a ccbe1 mutant.sup.12. Unexpectedly, loss of the EGF domains did not have any effect on the ability of CCBE1 to enhance processing of VEGFC in tissue culture cells. Thus, in vitro, the EGF and Ca-EGF domains are dispensable for the function of CCBE1 in VEGFC activation, and we would assume that this also holds true in vivo. However, as a CCBE1ΔEGF molecule cannot substitute for wt CCBE1 in mice and has reduced activity in increasing Vegfc signaling in zebrafish, the EGF domains do have a crucial function in vivo. The precise role of the EGF and Ca-EGF domains in vivo is not yet clear and needs further investigation in the future. It might be that this domain is necessary in other processes such as binding to ECM components. Consistent with this notion, a CCBE1ΔCollagen-Fc protein has been shown to bind to vitronectin, Collagen I, Collagen IV and Collagen V in an in vitro binding assay.sup.15. Alternatively the EGF domains could be involved in other aspects of VEGFC/VEGFR3 signaling such as receptor binding, possibly also mediated through prior or simultaneous interaction of CCBE1 with ECM components. Indeed, previously it has been shown that a recombinant protein that only contains amino acids 1-175 of CCBE1 was able to increase VEGFR3 phosphorylation when recombinant CCBE1 and recombinant pro-VEGFC were added to a culture of porcine aortic endothelial cells.sup.17. In this assay, CCBE1 increased binding of both pro-VEGFC and mature VEGFC to the receptor. Thus, it is tempting to speculate that the EGF domains are required to enhance binding of VEGFC to VEGFR3. However, we cannot exclude that if provided in high amounts such as through exposure as a purified recombinant protein, also the N-terminal part of CCBE1 can induce VEGFC processing. In a different assay, a cornea pocket assay, the N-terminal part of CCBE1 was able to enhance the lymphangiogenic effect of purified, fully processed VEGFC also indicating that the EGF domains of CCBE1 might be involved in other aspects of VEGFC signaling, perhaps enhancing binding of VEGFC to VEGFR3.

[0137] In all three different model systems tested we show that loss of the collagen domains has a profound effect on CCBE1 function. CCBE1ΔCol knock-in mice phenocopy the CCBE1 LacZ full knockout mice characterized by a failure of specified lymphatic endothelial cells to leave the cardinal vein. This was further confirmed by a total lack of enhancement of VEGFC signaling by ccbe1ΔCol in Tg(shh:vegfc) zebrafish and the inability of CCBE1ΔCol to induce proteolytic processing of VEGFC. In particular, the second collagen domain was found to be of higher importance, as both our zebrafish and our in vitro experiments show that loss of the second collagen domain alone strongly reduce the function of the CCBE1 protein. The crucial role of the collagen domains may be due to their involvement in direct activation of ADAMTS3. This is supported by the fact that co-expression of ADAMTS3 and CCBE1ΔCol did not synergize in VEGFC processing.

[0138] Our findings shed new light on the molecular defects that underlie HS and may provide a rationale that explains why so few HS mutations were found in the collagen domains. To date, most patients exhibit missense mutations affecting the N-terminal domain clustered in the EGF domain, the Ca-binding EGF domain or the cysteine rich domain upstream of the EGF domain. We could show that a mutation within the Ca-EGF domain inducing HS, C158R, and a mutation that leads to lymphatic defects in zebrafish, Ccbe1fof, does not affect the ability of CCBE1 to activate VEGFC processing in vitro and can still enhance Vegfc signaling in vivo, indicating that these mutations are hypomorphic alleles. In fact, the phenotype of ccbe1fof mutant zebrafish can partially be rescued by expressing high levels of full length Vegfc in the floorplate of zebrafish E. These results and the fact that a CCBE1ΔEGF molecule is partially active in vivo suggest that the HS mutations found within the EGF and EGF-Ca domains of CCBE1 are most likely hypomorphic alleles that retain some function.

[0139] In contrast, only one out of 13 patients identified so far harbors a mutation within the second collagen domain. This mutation, G327R, probably affects the secondary structure of the collagen repeat.sup.19. In our analyses we found that the G327R mutation strongly reduced CCBE1 function in vitro and in vivo, almost completely impairing its ability to activate VEGFC processing. This result is surprising as such a strong loss of function would most likely result in a complete absence of lymphatics and it is unlikely that many patients could survive that have mutations in the collagen-B domain. Therefore we consider it more likely that predominantly weaker alleles of CCBE1 are viable and can be found in patients, e.g. alleles that affect the EGF domain. Full loss-of-function situations are unlikely to be viable in humans. Of note, the only known patient bearing the G327R mutation is the only surviving child out of four siblings.sup.13. Furthermore, this patient is the only patient known to exhibit vascular defects in addition to lymphatic defects indicating that this mutation has a stronger effect than the other HS mutations found.sup.19.

[0140] Taken together our findings show that the collagen domains of CCBE1 are indispensable for its function in VEGFC activation in vitro and in vivo. The EGF domains are dispensable for this function in vitro, but are necessary for full activity of Ccbe1 in enhancing Vegfc/Vegfr3 signaling in vivo and for proper lymphangiogenesis in the mouse embryo. Contrary to the intuitive belief that the collagen domains bind to the ECM and that the EGF domain is more functionally relevant, we show here that it is the collagen repeat domain that is absolutely essential for enhancement of proteolytic processing of VEGFC by CCBE1, presumably by activating ADAMTS3. The role of the EGF domain should be subject of future investigations but previous work has indicated their capacity to bind ECM proteins. In zebrafish, ccbe1 is expressed along the migration route of lymphatic precursor cells; thus, it is possible that binding of the EGF domains to ECM components serves to direct specific locations of CCBE1 activity. At these dedicated areas the collagen repeat domains of CCBE1 mediate enhanced processing of VEGFC by activation of ADAMTS3. Thus, CCBE1 provides positional information for VEGFC signaling, which orchestrates the migration of LECs (FIGS. 7A and 7B). These molecular insights provide new entry points for therapeutical approaches to either stimulate or inhibit lymphangiogenesis by modulating CCBE1 function.

CITED ART

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TABLE-US-00002 List of sequences SEQ ID:NO 1 Human CCBE1 amino acid sequence, Accession code NM_133459 MVPPP PSRGG AARGQ LGRSL GPLLL LLALG HTWTY REEPE DGDRE ICSES KIATT KYPCL KSSGE LTTCY RKKCC KGYKF VLGQC IPEDY DVCAE APCEQ QCTDN FGRVL CTCYP GYRYD RERHR KREKP YCLDI DECAS SNGTL CAHIC INTLG SYRCE CREGY IREDD GKTCT RGDKY PNDTG HEKSE NMVKA GTCCA TCKEF YQMKQ TVLQL KQKIA LLPNN AADLG KYITG DKVLA SNTYL PGPPG LPGGQ GPPGS PGPKG SPGFP GMPGP PGQPG PRGSM GPMGP SPDLS HIKQG RRGPV GPPGA PGRDG SKGER GAPGP RGSPG PPGSF DFLLL MLADI RNDIT ELQEK VFGHR THSSA EEFPL PQEFP SYPEA MDLGS GDDHP RRTET RDLRA PRDFY P SEQ ID:NO 2 Human CCBE1 cDNA nucleotide sequence, Accession code NM_133459    1 cggccgcgga ggagcaggac gcttggtccg gacggagctc ggcgctggga agaagccggg   61 agcttccctg atggtgccgc cgcctccgag ccggggagga gctgccaggg gccagctggg  121 caggagcctg ggtccgctgc tgctgctcct ggcgttggga cacacgtgga cctacagaga  181 ggagccggag gacggcgaca gagaaatctg ctcagagagc aaaatcgcga cgactaaata  241 cccgtgtctg aagtcttcag gcgagctcac cacatgctac aggaaaaagt gctgcaaagg  301 atataaattt gttcttggac aatgcatccc agaagattac gacgtttgtg ccgaggctcc  361 ctgtgaacag cagtgcacgg acaactttgg ccgagtgctg tgtacttgtt atccgggata  421 ccgatatgac cgggagagac accggaagcg ggagaagcca tactgtctgg atattgatga  481 gtgtgccagc agcaatggga cgctgtgtgc ccacatctgc atcaatacct tgggcagcta  541 ccgctgcgag tgccgggaag gctacatccg ggaagatgat gggaagacat gtaccagggg  601 agacaaatat cccaatgaca ctggccatga gaagtctgag aacatggtga aagccggaac  661 ttgctgtgcc acatgcaagg agttctacca gatgaagcag accgtgctgc agctgaagca  721 aaagattgct ctgctcccca acaatgcagc tgacctgggc aagtatatca ctggtgacaa  781 ggtgctggcc tcaaacacct accttccagg acctcctggc ctgcctgggg gccagggccc  841 tcccggctca ccaggaccaa agggaagccc aggcttcccc ggtatgccag gccctcctgg  901 gcagcccggc ccacggggct caatgggacc catgggacca tctcctgatc tgtcccacat  961 taagcaaggc cggaggggcc ctgtgggtcc accaggggca ccaggaagag atggttctaa 1021 gggggagaga ggagcgcctg ggcccagagg gtctccagga ccccctggtt ctttcgactt 1081 cctgctactt atgctggctg acatccgcaa tgacatcact gagctgcagg aaaaggtgtt 1141 cgggcaccgg actcactctt cagcagagga gttcccttta cctcaggaat ttcccagcta 1201 cccagaagcc atggacctgg gctctggaga tgaccatcca agaagaactg agacaagaga 1261 cttgagagcc cccagagact tctacccata gcacatccca acaccgtcac gccaaaggaa 1321 gagaaagatc aactcacctg cagttaaacc atctaaagag aagaaagacc actggagacc 1381 tagaaaacat acatttttct cttctcttct cctgacgtct ctccactcct cttcttccaa 1441 atacgatgct attttcagag tcccctccta ggcctgcaga catgagggag tgaatgattg 1501 atttacctgc ttctcactaa gagtccattg gggtggtttg cattgtaact tttcttttac 1561 atcctatttt tccaggaact ttggatttaa gtactctcac agtgtcttaa atcataaatt 1621 cttgaagtta aatttggcag agtatcaaaa gggggaaaat gacaaagtga gctctaagaa 1681 aatgtgaggc tacttctaag atgtgtgttc acaatagacc ataactcctc tagtatcaaa 1741 attggggctc ttcagttaaa aaggggtggg gaggacaaac gtgtcgatgt gctttggtgg 1801 agaatttttt ccttgtgctt ctagtagact ttaaatattg tatccctttg tcaaaccttg 1861 tttcccaaat tcaattaaag agaggagaga attgaatggc gtttagagaa gatagaaaag 1921 aatcacagtc atatatttac tgttatatag attgccacat tctaaaattc aaatacggtg 1981 cttaaggttt catgccatgc ttatctgtaa gtatcctatt tagggaagaa gattaaactc 2041 tcttttcaaa aaaacaaagt gaaatgcctg gattcacatt aaaacaatgg gctctcgttt 2101 gctataatat tttaaagctg tttaatcaac agtggagtct gctctataaa tatagattat 2161 ttgttcaata aactggctga gcttagagag aggtgcagaa ttcctggttc tgagcaggtg 2221 cccagaaggt accattaggt gccatgatcc aggctgaacc aatatacagt ggggctgaag 2281 tctgcaagga ggttgctggc ttgggctgac ctcactaatg ccatcagcag cggtaggtaa 2341 attttttctc cttgggtatt acaagttttt gtctggagcc aaccaagctt gccaccaaca 2401 tattgagagt aatacactat tgaaagttat cttggatggg gagaaaaaaa aatagtggtt 2461 ttccttgttt gcaaaaactt ccttcctatt ctcatttttt cttaattttc tttaatttag 2521 tccaagttcc agttctttta ggccttctct ttgatttatt ttcccctgca tgtgagaagc 2581 agttcagaaa aaggtctata tctccacctc ctagtgagtt agagtgtttt ctcagagcac 2641 ctctgggtgg caaagggaag catgttcctg ccaaggtttg ctgtggattc agaagcacca 2701 ggagcaagag accagaagga tgatctgctc ctttgtaacg ttgttgaggg ccctcttgtt 2761 tccaatgagc agcttatagg ttactcacag tccactttct cactggacac acaaagtggc 2821 tctttatcta cctttgcggg agattttcac tctcctgcaa atgatcgttc tcacactcat 2881 attagctcat gttggaattt cccatcctgc catgtccttt cccatttctt tttggctttt 2941 ttgcctccac cttttagccc acatcattta actccactac tgtgaaagct tgcttaaaga 3001 aaatccctct tggccgggtg tggtagccca cgcctctaat cccagcactt tgggaggctg 3061 aggcggggag atcacaaggt caggagatcg agaccagcct gaccaacatg gtgaaaccct 3121 gtctctacta aaaatacaaa aattagctgg gcgtgttggc acacacctgt aatcccagct 3181 actcaggagg ctgaggcagg agaattactt taacctgcgg ggggagccta gattgcgcta 3241 ctgcactcca gcctaggcaa cagagggaga ctctgtctca ttaaaaaaaa aaaaaaaaaa 3301 aaaaaaaggc cgggcttggt ggctcatgcc tgtaatccca gcactttggg aggccgaggc 3361 gggcggatca cgaggtcagg agatcgagac cacagtgaaa ccctgtctct actaaaaaca 3421 caaaaaatta gtcgggcgtg gtggtgggcg cctgtggtcc cagctgctcg ggaggctgag 3481 gcaggagaat ggcgtgaacc tgggaggcgg agcttgcgct gagccgagat cgtgccactg 3541 cactccagcc tgggcgacag agcgagactc tgtctcaaaa aaaaaaaaat atcccttttg 3601 ttgtgtttga atgccacctt tcagtcttct tccttaagaa tgttaggaag gggctttgca 3661 aacctctagt ggcaacagtc ttccttccct tcttcctacc acgttggaaa tgcaggactc 3721 atgtcagtca gcatgtgacc gagtctttca tgaacacttt gctcctctat gtctcattta 3781 tgcaaaattc ctggtgactc tccactaaca tttttaaagt gaaagcaaac tttcacttta 3841 aaaaaagtga gcgagaggat cccttgagcc caggagttca aggccagtct gggcaacata 3901 gcaagacccc atccctaaaa aaaaaaaaat aagttttatt aaatgtggca ctttccccta 3961 gaagggcagt aaccccagga accagtctgc ctcttttcga ataaaggaga ctttttaaaa 4021 agaaaaaatt tctttttagg gtggggtgct ctttatctag catctttcct tcctccttct 4081 ctctgcaaaa ttcaacattc atgacagagg gccacaccaa ccacgggttt atagagagag 4141 gaactgaaca gctgttgatt cccatctgga atatatttaa tgtttgcctg cttgtggagc 4201 atggtattta aagggtgtgg atggatgaat gtttaaaaaa aaacacacaa aactatgcac 4261 aagctgtatg agagatggct aggtccatct atgatttttt ttaaaagaag aattttaata 4321 ccttttcttt gacagtgaac tgtatttaga aatatgatct ttattgtgaa atgctcataa 4381 aatgcaacca aactgcatgt ttggccatag gctagaataa tatattaaaa gaattaatgg 4441 aaagtagtat tgtctgggtt tcatgaaact attccagata atattctcca gcaaaactta 4501 tggtaacctg tattttataa tgtcaatctg ctggaccaag ttaatttaga aaataatttt 4561 taatcctcag attttcaaaa cttggactac tgcaagactg atatgtactt tttatgccca 4621 aatcatattt ttcaaagata ggacatcata aggcatcatt atttctaatg tatcttttaa 4681 ctagatagaa aaagctttac tgtctaaaca ggacttctgc tcaaaaccta atgggaaagc 4741 tatttctggg gtaagatttg taacagtgct tctaggtcat ttcatgtttt atagggaaaa 4801 agatctttgt acacctcctc aacctgttag tagaaatgtt gacttcgatt ttttgcaccc 4861 tcttcacagg acctcataag ttgcctctgt tcttggaaag caatgggaat aaaaatatgc 4921 tgttgaaaat agtgcatggg gccaggcaca gtggttatgc ctgtaatccc aacactttgg 4981 gaggctgagg cgggcgcatc atgaggtcag gagatcaaga ccatcctgac caacacgtgg 5041 tgaaacccca tctctactaa aataaataaa aaaaaaaatt agccaggcgt ggtggtgcac 5101 gcctgtagtc tcagctactc gggaagctga gacacaagaa ttgcttgaac ccgggaggtg 5161 gaggttgcag tgagccaaga ttgcgccact gcactccagc ctggctacag agtgagactc 5221 cgtctcgaaa aaagaaaata gtacatggag ggcatgcatt ttagtttagg aaacccccct 5281 cccttcccag ttccagaggg agaaattata agctatactg tgccaaaagt gagtggggct 5341 gcagagagaa tggtgccttt tctcaccttc tgagttaatg cccgacatct gccattggat 5401 tcattgacca aaggaagtca tttctactgt ataaactcag gagtatcata gcccaacaag 5461 taaataataa atgttcattg gttttggaag gaaggaaagg tgagtattac cccaccaaat 5521 accagcgaag agcaccctgg ctttggccat ctttccaagg ttcataattg ctgtgggcct 5581 ggtgagccct gttcccaggt atgcaaggga gggcttctcc aggccagaca tttctgtagg 5641 ttttcaggta gcaactcccc catcatattt tgggtgtcat tccccactct ctctccccac 5701 ttctcagcct gtgccccaga aacaaccaca gcagcctcat tctgcagact taacatctgt 5761 caaataacct tcctgaaaag gaaagttatt ggaggaatcc aggccaaaca acaagtagaa 5821 tagagccatc taaagttatt aataatgagt tcagggaaat agatgaattt tttcctggca 5881 tagtcaatat ttatatctca caacaagtca aaaataattt tccatttgga aaacaaaaca 5941 caccatgact gtaattgtta aggcatataa tcatgaactt cacatgctcc ctcaacaaac 6001 gttactgctc tagggaaatc atagaaaagg accctcttac tccccagggg atcaaagcaa 6061 gtccccttag gaatttcatg tgtgccgtgg gtctgttttt atttcacagt gactagtcat 6121 atactggagt agctctgttg ttcattattt gtaacaggtc catgtaacag tcaagttagc 6181 attcaagcaa ttatggatgt gatactatga tgtacttttg ttatgattgt atatgcttaa 6241 taacaaagtt atttttctta aaaaaaaaaa aaaaaa SEQ ID: NO 3 Mus musculus CCBE1 amino acid sequence, Accession code NM_178793.4 MVPPP LPSRG GAAKR QLGKS LGPLL LLLAL GHTWT YREEP EDRDR EVCSE NKITT TKYPC LKSSG ELTTC FRKKC CKGYK FVLGQ CIPED YDICA QAPCE QQCTD NFGRV LCTCY PGYRY DRERH QKRER PYCLD IDECA TSNTT LCAHI CINTM GSYHC ECREG YILED DGRTC TRGDK YPNDT GHEEK SENEV KAGTC CATCK EFSQM KQTVL QLKQK MALLP NNAAE LGKYV NGDKV LASNA YLPGP PGLPG GQGPP GSPGP KGSPG FPGMP GPPGQ PGPRG SMGPM GPSPD LSHIK QGRRG PVGPP GAPGR HGSKG ERGAP GPPGS PGPPG SFDFL LLVLA DIRND IAELQ EKVFG HRTHS SAEDF PLPQE FSSYP ETLDF GSGDD YSRRT EARDP EAPRN FYP SEQ ID: NO 4 Mus musculus CCBE1 cDNA nucleotide sequence, Accession code NM_178793.4    1 gaaggcggct gcggccgcgg agcctccctg ggcacagcgc agggagagag ctcgggcgcc   61 gagaagaagc cgcgagcttc cccgatggtg ccgccgcctc ttccgagccg gggaggagca  121 gccaagaggc agctgggcaa gagcctgggg ccgctgctgc tactcctggc gctgggacac  181 acgtggacct accgagagga acccgaggac cgcgacagag aagtgtgctc tgaaaacaag  241 atcaccacga ccaaataccc atgtctgaag tcttcgggcg agctcaccac gtgcttcagg  301 aaaaaatgct gcaaaggata taaatttgtt cttggacagt gtattccaga agattatgac  361 atttgtgccc aagctccctg tgaacagcag tgcacggata acttcggccg tgtgctgtgc  421 acgtgctacc cgggataccg atatgaccgc gagagacacc aaaagcggga gagaccgtac  481 tgtctggata tcgatgaatg tgccaccagc aataccactc tctgtgcaca tatctgcatc  541 aacaccatgg gcagctacca ctgtgagtgt cgggagggct acatccttga ggacgatggg  601 aggacctgca caaggggaga caaatacccc aatgacactg ggcatgaaga gaagtccgag  661 aatgaggtga aagccgggac ctgctgcgcc acatgcaaag agttctccca gatgaagcag  721 accgtgctgc agctgaaaca gaagatggcg ctgctcccca acaatgccgc tgaactgggc  781 aagtatgtca atggtgacaa ggtactggcc tcaaacgcct accttccagg acctcctggc  841 ctgcctgggg gacagggccc accaggctca ccaggaccca aggggagccc tggattcccc  901 ggtatgccag gccctcctgg acagccaggc ccacggggct caatgggacc tatgggacct  961 tcccctgacc tgtctcatat taagcaaggc cggaggggcc ccgtgggccc accaggagca 1021 ccaggaagac acggctccaa gggggagaga ggagcacccg gacccccggg gtctccggga 1081 cccccaggtt ctttcgactt cctgctgctt gtgctggcgg acattcgaaa tgacatcgca 1141 gagctgcagg agaaggtgtt tggacaccgg actcactctt ccgccgagga cttcccccta 1201 cctcaggaat tctccagcta cccagagacg ctggactttg gctctggaga tgactactcc 1261 agaagaactg aagcaaggga ccccgaggcc ccaagaaatt tttatccata gcacatccca 1321 tatcctcacg ccaccagaag agaagcatgc cttcgacctt ccccttactc tgtttccaaa 1381 cccggttttc caagtttcct gtgcatcaca ctagcaacag gaagatgtga tgggttaacg 1441 tgctgttctt gaagagccaa tgggtggttg acatcaagac tttcttcaac gtccgatttt 1501 ttcaagagct tttgggtttc tgagttcatc attccacaga atcttcaact ttggcagagt 1561 gcaaaagagg ggaaaatggc accgtgggtt cttaggagtg taaggttcct tctaaaaaga 1621 aaataatgtt caaatgcttg actattcatt ccctactgtc aggagtaagg cttttagggt 1681 gggggtgggg gtggaggggc atggaaggag caaccatgga gaataacatt gatagaaaat 1741 gattttcctt agcaatatcc cagatttcaa attctgcatc ctattttcca acttgatggg 1801 ggtttttttt tgtttgtttg ttttggtttg gttttttgtt ttttgggggt gtttgtttgt 1861 ttgtttgtct ttaaatttgg ttacagaaac aagagattgg aaagaatgtg ttcagagaga 1921 tagagaatta gccttatatt tcctgtctca taggttgccg aatttagaat tcagatacga 1981 cagtcattga ttcgtgcaaa tcctatgtgg aggagggagt ttgtttgtaa gggcttgatc 2041 atgttttcta gggagcttgg ggtgaggaaa cactctgtgc atactagaac agagggctcc 2101 tggagaccag gacgattgaa gactacatgg tcaaaagcat tgtcctgctc catacatgtt 2161 gatgatttgt gaaataagat ggctgacatt taagaagaag tacaagatgc cctggcactg 2221 acagggttgc cagatgtgcc agcaaggcct gatccaggct gaatcaaggc tggagggaaa 2281 tcactgccct ggaatcttag ccaaggatgt caaggggaca ttgagaagtg cttcactaaa 2341 atcagattaa tcagaagcag attaatctac tcttaagaga tttgaagttc tcaccagggc 2401 acacttggaa cagcatacag ctgagaggtc tctgagatag agaaggagga ggagtttttg 2461 ataaattgga ataattttcc actatttgcc ccctgatttg gttagaatcc ctgttgttct 2521 gggtgtcctt gactttttgt cctgggccac aaggaaacgg cttggaggcc agcacatttc 2581 ccaatgtctc cctaagtccc ttcttggagt atgtctagat ccccagggaa tcatgttccc 2641 agaaaggagc aagaggccag caggttcctt cttggtatct ctgggttctt gtttcaggga 2701 tctgcttccg ggctccttag tgaacacttt ctccttgggt gtgcagcagg ctccgtgatc 2761 ttgctcacat ggttgcccac accagggtcc cagtttgcta tcctgcagtg cccccttata 2821 tttctaagaa gtttgagatt gcattgatct tttccctata tcacttaagc ctccatcgtc 2881 ttcccacacc tactgtgaca gcttgttgga ggaaacagct attggtttgc atgacactgc 2941 atccaccatc cactcttctt tctgagcaat aagaaggggc tctgtctaca gagccagcca 3001 gagcctcgtg ggctttcact tcccctctcc cacctcccta ccctcatccc tctctcctgg 3061 ttctcttcct tttccttttt tttctctctt cctctcctcc tcttttgctc cttctctcct 3121 tcatttcctc tacccctatc ctagcttccc tgcctttcca cctctccttt cttacttgct 3181 tccttcctcc ctccttccct ccctcccttt ctccttctct ccctccatct ttcttccttt 3241 ctactccctc cctcccttcc tacctaccta cttccttcct tccctttttt cttccttagt 3301 tccctctctc tgctccctcc ctccttccct ccatgcttgc ctgcctatct tcctacccag 3361 ttagaaaggc aggattccca cacactccca cccaaatccc cagtggctgt ccatcagcag 3421 tcctgatgaa ggcaagcaca cacttgcatc gcttgcttgc tgtctcaccc tccttccccc 3481 ttcagtctct cctgaacctg tgcatcacca cagatagcct tgtcaactgt ggcttcctga 3541 agagatggat gcaaccgcag tcaagtgcca cctggaatct atttagtgct tgcctgctta 3601 tagaacccat cttttaaagg gtgtggatgg atgaattctc aaaactatgc acaggctctg 3661 tgagcaataa ttatgtccat ctttttttat gaggaatttt ataactactt tttatgtcta 3721 ctttttttag acagtgaaat gtatgtagaa atataatctt tattgccaaa tgctggtaaa 3781 acgcgagcac actccatgct tggctggagg ccaggataat gtactgaaag aatgaagaga 3841 aagtcataat atctgggatt catgagtctg tctagataat tacctccagg aaaacataat 3901 agcctatatt ttgtgatctc aatatgccat gtcaatttag ataatcgtta ctcctcagat 3961 tttcaaaaca tggaatacta actaactaca agaccaacgc atgtcctcta cttattcaaa 4021 tcatggattt ttagtgataa agcattattg ctcccatatc ttttagttgt ggacagaaaa 4081 aaaaatcaaa gcttttctgt ctaaacaaat ttctgctcaa aatatcatag gaaggccttt 4141 gggaggaagg acagttcaga acaaatttac cgagtcactt catatctcac agggaaaata 4201 ttttagtttt ttatacgccc ttcaacactt tagtagaaat ggtcaacttt tctaatattt 4261 ccactggtta agacttggtt atgaattgcc tctgtgttta taaagcaatg agaataaaat 4321 ttcactgaaa ataatataaa gaagactttc attttagttt aggaaaactg aattttccaa 4381 ttccagaagg aaaaaaataa ccagttttcc tgtgccagtt aagtgttagg agctaggtgt 4441 gatggtggac acctgtaatc ccagcacctg agaagcacag ctaggcagat caggagttca 4501 aggtcagcct cagctacata acaagtgtga ggccagcctg ggctatctga gagtctatct 4561 caaaataata atgatgatga tgataatgtg atgataataa agaataataa ttagcagagg 4621 actaaagaga tggctcagag gttaaggatt cttgctgctc ttccagagat acagagctca 4681 gtttccagct cttgcacagg cagctcacaa catctgtaaa cacaggtcca ggtgatctgg 4741 cgccctcttc tggcttccat agtacctgca ctcacatgca cacacacaca tagatataca 4801 aacacataat tacaaataaa gtctttttta aaggagtggg tacaaagagg atgctgcctt 4861 ttcttgcttt ctatgttact ttccaatact tgctacggaa ttaactaaag tcatattgct 4921 gtgtggagcc aggccactat ccagcaggaa aattataagt gcccagtgat cttggaagaa 4981 gttttggccc atcaaaggcc aggtgcagag caccctggta gacccaggta agtcatgttc 5041 cctttccaag gttctgaaca tccttggcct tggaagtacc actatcaggc acattggcac 5101 aaaacttctt catgaccatc catcaaactt taccttgagg tctcaggaag ccacccccct 5161 atcttatttt gagcatcatt tttcattttc ctcctcttcc aaattcaaac agacagcctc 5221 aggagcctcc ttctgcaagc ttatcttcca gacaactgtt ctaaaaggga aagctattgg 5281 ctggaatctg agccatacaa ttagtaatat agaggcttct gttctattca gggaaataca 5341 tgggtcattt cctgatgcag caatcatgta tgtttcacaa catgtcaaaa ataattttct 5401 ctttggattt ttcaagggcc gtcattgtta aagctgaaat ggtgtgcttt atatactctt 5461 cctacaaatg ttaccatcag agaggaacca tgaaaaagga catatgggct atccatccct 5521 cagagagctc agtatgtttt gtccgattcc cagagcttga tccctgagtg gttcttgagt 5581 ctgtttttat ttctcagtca ctggtcatat atttcagtat ctctgtgcat tatttatatc 5641 agatcttgta acagtcaaac tgatattcca acagtcatgg atgtaatact aggaagtgcg 5701 tttgtatgac tgtatatgct taataacaaa gttatttttc tt SEQ ID: NO 5 Danio rerio CCBE1 amino acid sequence, Accession code NM_001163923 MIYPG RGASL SVAVA LVLFS SGAPW TFREE KEDVD REVCS ESKIA TTKYP CVKST GEVTT CYRKK CCEGF KFVLG QCIPE DYDVC AGAPC EQQCT DHFGR VVCTC YDGYR YDRER HRNRE KPYCL DIDEC ANNNE TVCSQ MCVNT PGSYR CDCHS GFYLE DDGKT CTKGE RAPLF EKSDN VMKEG TCSAT CEDFH QMKMT VLQLK QKMSL LSSNT EINKQ MTNEK MMMTT NSFLP GPPGP PGPAG TPGAK GSSGS PGQMG PPGLP GPRGD MGPIG PSPDL SHIKQ GRRGP VGPPG APGRD GMKGE RGFPG PSGPP GPPGS FDFLL LMMAD IRNDI AELQS KVFSR PLHSS FEDFP SAPDS WRDTP ENLDF GSGED YKSQS PPKSS RKRKL PRNLK NPDWP V SEQ ID: NO 6 Danio rerio CCBE1 partial cDNA nucleotide sequence, Accession code NM_001163923    1 ggaatctgcg cgtggggctt cgcaggaggt aaccaatcaa tactctccca attcctccga   61 aacaagcgct gaacttcaag actggattta aagggacaaa tatcttttaa tcatctcaga  121 gtgtctgaaa tgatctaccc gggcagagga gcatctctca gtgtggccgt ggcgctcgta  181 ctgttctcat cgggagctcc gtggactttc cgagaggaga aggaggatgt agacagagaa  241 gtgtgttcag aaagcaaaat cgcaacgacg aagtacccgt gcgtaaagtc cactggagag  301 gtgaccacat gctacagaaa gaagtgctgt gaaggtttca agtttgtcct gggtcagtgt  361 attccagaag attatgatgt gtgtgccggc gccccgtgtg aacagcagtg tacggatcat  421 ttcggtcggg ttgtttgcac ctgctatgac gggtatcgat atgaccggga acgacacaga  481 aacagggaga aaccatattg cctggacatt gatgaatgtg ccaacaataa cgagactgtg  541 tgctcacaga tgtgtgtgaa cactcccggc agctaccggt gcgactgcca cagcggcttc  601 tacctggagg atgatgggaa gacatgcacc aagggcgaga gagctccact ctttgaaaaa  661 tcagacaacg tcatgaaaga aggcacgtgt tcggccacat gcgaggactt ccatcagatg  721 aagatgactg ttctccaact caaacagaag atgtccttat tgtcgagcaa caccgagatc  781 aataagcaga tgaccaatga aaaaatgatg atgacgacaa attcattttt acctggacct  841 ccagggcctc ctgggcctgc agggacgcct ggagccaaag gatcctctgg ctctcctgga  901 cagatggggc caccaggctt acctggtccc agaggtgaca tgggacccat tggaccctcc  961 cctgacctgt cgcatatcaa acagggtcga cgtggcccag tgggtcctcc tggggctcca 1021 gggagagatg gcatgaaggg agagcgaggg tttcccggcc cttccggacc tccaggccca 1081 ccaggatcct ttgacttcct gttactcatg atggctgaca ttcgtaacga catcgctgag 1141 ctgcagagta aagtcttcag cagaccgtta cattcttcat ttgaggattt cccatctgcc 1201 ccggacagct ggagagacac accggagaac ctggacttcg gatccggcga agactacaaa 1261 tcccagagcc ctcccaagag cagcaggaag aggaaattac ctcggaactt aaaaaatccc 1321 gattggccgg tttgagactg tcagtaaaca atacaagaac tgaaaaaact gatggtgtaa 1381 atattacaga atgactgcta tttaactgta tactcgctga ggaaagaagg ctgaatatat 1441 ttcactgtat gaaatttcta tttttataac ataaaagatg tacatttttt gtaaaaaaaa 1501 aaaaaaaaaa aaaaaaa SEQ ID: NO 7 Human CCBE collagen domain B GRRGP VGPPG APGRD GSKGE RGAPG PRGSP GPPG SEQ ID: NO 8 Human CCBE1 collagen domain A LPGPP GLPGG QGPPG SPGPK GSPGF PGMPG PPGQP GPRGS MGPMG P