Cell line with METTL3 gene knocked out, its construction method and interference vector

Abstract

A pig intestinal tract epithelium cell line with METTL3 gene knocked out and a construction method therefor. A gene interference vector for METTL3 form a pig is also provided.

Claims

1. A method for constructing METTL3 gene knockout cell line, comprising: processing gene knockout by an m6A methyltransferase gene Mettl3 to obtain a pig intestinal epithelial cell line which is capable of tolerating LPS (lipopolysaccharide) stimulation led fatty acid absorption disorder; comprising steps of: (1) designing shRNA according to the m6A methyltransferase gene mettl3, wherein sequence of the mettl3 is shown in SEQ ID No.1, and sequence of the shRNA is shown in SEQ ID No.2 and SEQ ID No.3; (2) phosphorylating m6A methyltransferase gene mettl3 shRNA; (3) connecting the phosphorylated mettl3 shRNA to Lentivirus Expression Vector to obtain a mettl3 shRNA lentivirus expression vector; (4) enveloping the mettl3 shRNA lentivirus expression vector obtained in step (3) with 293A cells; (5) infecting the mettl3 shRNA lentivirus obtained in step (4) with intestinal epithelial cells, and then by puromycin, screening and obtaining the intestinal epithelial cells which are genetically modified to knock out the m6A methyltransferase gene mettl3.

2. The method according to claim 1, wherein the construction method of the mettl3 shRNA lentivirus expression vector comprises steps of: step (1) digesting the expression vector of shRNA lentivirus by bbsI, and obtaining the linear vector by gel recovery; step (2) obraining phosphorylated mettl3 shRNA, and connecting the expression vector of prsi9-u6 lentivirus by T4 ligase.

3. A pig intestinal epithelial cell line obtained by the establishment method according to claim 1, which is resistant to LPS stimulation leading to fatty acid absorption disorder.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a Agarose gel electrophoresis to identify the Mettl3 shRNA lentivirus expression vector by PCR;

(2) FIG. 2 is a schematic diagram of pRSI9-U6 lentivirus vector;

(3) FIG. 3A is a diagram showing Western blot results of Mettl3 protein expression level after Mettl3 shRNA lentivirus infecting epithelial cells;

(4) FIG. 3B is a diagram showing a transcription level of Mettl3 in intestinal epithelial cells after gene editing;

(5) The mean value of data represents three biological repeats, and the error line represents standard error (SE). Significance analysis * means P<0.05, ** means P<0.01.

(6) FIG. 4 is a diagram showing fatty acid absorption of gene editing intestinal epithelial cells edited by laser confocal scanning microscope;

(7) FIG. 5 is a diagram showing fatty acid absorption of gene editing intestinal epithelial cells by flow cytometry. The left part is the fatty acid absorption of different treatment groups, and the right part is the quantitative statistics of the left figure. The average value of data represents three biological repeats. The error line represents the standard error (SE). Significance analysis * means P<0.05, ** means P<0.01.

(8) FIG. 6 is a diagram showing absorption of fatty acids in gene edited intestinal epithelial cells by ultraviolet spectrophotometry; the average value of data represents three biological repeats. The error line represents the standard error (SE). Significance analysis * means P<0.05, ** means P<0.01.

(9) FIG. 7 is a diagram showing effect of Mettl3 plasmid infection on fatty acid absorption in Mettl3 knock-out intestinal epithelial cells.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

(10) The invention will be further described in combination with the attached drawings and embodiments.

Example 1. Acquisition of Mettl3 shRNA Lentivirus Expression Vector

(11) Mettl3 shRNA in the invention was designed with online shRNA design tool: http://www.broadinstitute.org/rnai/public/seq/search; Mettl3 gene sequence is shown in SEQ ID No.1, shRNA sequence includes upstream sequence P1 and downstream sequence P2, as follows:

(12) TABLE-US-00001 P1 (upstream sequence): (SEQ ID No. 2) ACCGG GAGATCCTAGAACTATTAAAT CTCGAG ATTTAATAGTTCTAG GATCTC TTTTTTG; P2 (downstream sequence): (SEQ ID No. 3) CGAACAAAAAA GAGATCCTAGAACTATTAAAT CTCGAG ATTTAATAGTTCTAG GATCTC C.

(13) Mettl3 shRNA was phosphorylated by T4 Polynucleotide Kinase at 37° C. for 30 minutes, then at 95° C. for 2 minutes and natural cooling to room temperature.

(14) The expression vector of shRNA lentivirus was digested by BbsI and recovered by gel to obtain linear vector; the phosphorylated Mettl3 shRNA was incubated with T4 ligase at room temperature for 2 hours and then connected to the expression vector of pRSI9-U6 lentivirus. The strain DH5 α was transformed by heat shock method and the plasmid was extracted for PCR identification. The primer sequence is as follows.

(15) TABLE-US-00002 (SEQ ID NO. 4) Forward: 5′-GAGGGCCTATTTCCCATGATTCC-3′, (SEQ ID NO. 5) Reverse: 5′-ACAGTCCGAAACCCCAAACGCACGAA-3′.

(16) The reaction conditions were 94° C. pre-denaturation for 3 min, 94° C. denaturation for 15 s, 56° C. annealing for 30 s, 72° C. extension for 2 min, 25 reaction cycles to obtain the positive clones. As shown in FIG. 1, the PCR products of the selected clones were larger than those of the negative control group, indicating that the shRNA of Mettl3 was indeed inserted into the expression vector of pRSI9-U6 lentivirus as shown in FIG. 2.

Example 2. The Envelope of Mettl3 shRNA Lentivirus

(17) 2 μg of the Mettl3 shRNA lentivirus expression plasmid obtained by the method in Example 1 was transferred into lentivirus element 0.25 μg VSVG and 1 μg PsPax by lipofect Libo2000; after 24 hours, it was replaced with 1.5m1 complete culture medium; after 48 hours, the virus was collected to obtain Mettl3 shRNA lentivirus.

Example 3. Gene Editing of Intestinal Epithelial Cell Line

(18) 500 μL of the Mettl3 shRNA lentivirus obtained by the method in Example 2 was added to the intestinal epithelial cell IPEC-J2, which was transformed into a complete medium 24 hours later, and 4 μg/mL purinomycin was added 48 hours later for screening. Finally, the intestinal epithelial cell with Mettl3 gene edited was verified by fluorescent quantitative PCR and Western blot. As shown in FIG. 3A-3B, the expression level of Mettl3 in intestinal epithelial cells of the Mettl3 shRNA lentivirus infected group was significantly lower than that of the empty vector group.

Example 4. Analysis of Fatty Acid Absorption of Gene Edited Intestinal Epithelial Cells by Laser Confocal Method

(19) The Mettl3 knock-out intestinal epithelial cells obtained by the method in Example 3 were stimulated with 100 μg/mL lipopolysaccharide (LPS) for 0 hour, 3 hours or 6 hours respectively with normal cells (Scramble) as control; the fatty acids labeled with BODIPY were added and incubated at 37° C. for 5 minutes, and the absorption of fatty acids was detected by laser confocal. The results showed that the tolerance of Mettl3 knock-out intestinal epithelial cells to LPS stimulation induced fatty acid absorption disorder was significantly higher than that of normal cells. As shown in FIG. 4, LPS stimulation was carried out for the control group and Mettl3 knock-out intestinal epithelial cells respectively. The results showed that the absorption of fatty acids in the control group was significantly blocked under LPS stimulation, but Mettl3 knock-out intestinal epithelial cells showed obvious tolerance.

Example 5. Gene Editing of Fatty Acid Absorption in Intestinal Epithelial Cells by Flow Cytometry

(20) The Mettl3 knock-out intestinal epithelial cells obtained by the method in Example 3 were stimulated with 100 μg/mL lipopolysaccharide (LPS) for 0 hour, 3 hours or 6 hours respectively with normal cells (Scramble) as control; the fatty acids labeled with BODIPY were added and incubated at 37° C. for 5 minutes, and the absorption of fatty acids was detected by 488 nm wavelength flow cytometry. The results showed that the tolerance of Mettl3 knock-out intestinal epithelial cells to LPS induced fatty acid absorption disorder was significantly higher than that of normal cells. As shown in FIG. 5, the control group (Scramble) and the Mettl3 knock-out intestinal epithelial cells (shMettl3) were stimulated with LPS for 0, 3 or 6 hours respectively.

Example 6. Detection of Fatty Acid Absorption in Gene Edited Intestinal Epithelial Cells by UV Spectrophotometry

(21) The normal and gene edited IPEC-J2 cells were seeded with gelatin coated, 96 well, black or transparent plates respectively. After overnight culture, the serum was starved for at least 8 hours with FBS free medium, treated with 1 mg/mL LPS for 0, 3, 6 hours, and then washed briefly with phosphate buffered saline (PBS). At the same time, add BODIPY FA (molecular probe γ-D3823) and fatty acid free bovine serum albumin (BSA) (2:1 molar ratio) into PBS and pre-incubate in 37° C. water bath for 10 minutes; after adding cells, incubate at 37° C. for 5 minutes, wash twice with PBS added with 0.5% BSA, each time for 2 min, in order to inhibit the extracellular fluorescence, add 0.4% trypan blue (50 μL per pore), and measure immediately with ultraviolet spectrophotometer. Intracellular fluorescence was measured (488 nm for excitation, 515 nm for emission, 495 nm for cut off). As shown in FIG. 6, the control group (Scramble) and the Mettl3 gene edited intestinal epithelial cells (shMettl3) were stimulated with LPS for 0, 3 and 6 hours respectively. The absorption of fluorescent labeled fatty acids was detected by UV spectrophotometry.

Example 7. Effect of Mettl3 Plasmid Infection on Fatty Acid Absorption of Intestinal Epithelial Cells

(22) The Mettl3 knock-out intestinal epithelial cells obtained by the method in Example 3 were transferred with pcDNA3.1empty plasmid and Mettl3 plasmid by Lipo2000. 24 hours later, 100 μg/mL LPS was used to stimulate for 0 hour, 3 hours, 6 hours respectively. The fatty acid labeled with BODIPY was added and incubated at 37° C. for 5 minutes. The absorption of fatty acid was detected by flow cytometry (wavelength 488 nm). The results showed that compared with the empty body group, the fatty acid absorption level of Mettl3 plasmid group decreased significantly under LPS stimulation, which indicated that Mettl3 played an important role in the tolerance of fatty acid absorption disorder. As shown in FIG. 7, the intestinal epithelial cells with Mettl3 gene knocked out by gene editing were transferred into pcDNA3.1 empty plasmid and Mettl3 plasmid, and then LPS stimulation treatment was carried out for 0 hour, 3 hours and 6 hours. The absorption of fluorescent labeled fatty acids was detected by confocal laser.