稀有鮈鲫卵膜zp基因敲除和转基因斑马鱼构建

EGG CHORION ZP GENE MUTANTS AND TRANSGENIC LINES CONSTRUCT IN RARE MINNOW AND ZEBRAFISH

  • 摘要: 通过稀有鮈(Gobiocypris rarus)卵膜蛋白质组测序鉴定黏性卵膜中富集的透明带蛋白(Zona pellucida glycoproteins, Zps), 建立可用于卵型研究的稀有鮈鲫 zp 基因突变体和转基因斑马鱼(Danio rerio)。实验收集稀有鮈鲫胚胎(1hour post fertilization, hpf), 分离收集足量卵膜, 提取卵膜中的蛋白质进行测序分析。将测序数据进行拼接并与鲤科鱼类蛋白质进行比对, 选取匹配度和丰度最高的基因 zp2l2zp4l 进行实验。分别在 zp2l2zp4l 的第一个外显子、第六个外显子设计 CRISPR/Cas9 敲除靶点, 构建 zp 基因突变体。扩增斑马鱼 zp3.2 基因上游启动子序列(2874 base pairs, bps)和 zp2l2zp4l 编码序列(1137、3009 bp), 通过无缝克隆(In-fusion cloning)将 zp3.2 启动子连接进入具有 Tol2 转座元件的质粒中, 构得质粒 pT2AL-zp3.2-eGPF; 再将 zp2l2zp4l 编码序列克隆到 pT2AL-zp3.2-eGPF 质粒中, 得到可用于胚胎注射的转基因质粒 pT2AL-zp3.2-zp2l2-eGPFpT2AL-zp3.2-zp4l-eGPF。体外转录合成转座酶 mRNA 与构建的转基因质粒混合进行斑马鱼胚胎显微注射。通过稀有鮈鲫胚胎显微注射及三代鉴定, 成功在稀有鮈鲫中敲除 zp2l2zp4l 获得稳定遗传的纯合突变体; 稀有鮈鲫 zp 转基因斑马鱼经传代鉴定, 筛选得到了可稳定遗传的转基因品系 Tg(zp3.2:zp2l2-eGPF)Tg(zp3.2:zp4l-eGPF), 这 2 个转基因品系的绿色荧光蛋白在斑马鱼胚胎发育的 15d (days post fertilization, dpf)开始在卵巢和肝脏中表达。实验构建 zp2l2zp4l 稀有鮈鲫突变体和转基因斑马鱼的方法, 为鲤科鱼类卵型形成机制的研究提供了可行的实验思路和技术路线。

     

    Abstract: This study aims to identify the zona pellucida glycoproteins (Zps) enriched in the sticky egg chorion of the rare minnow (Gobiocypris rarus) by sequencing the egg chorion proteome, and further aims to construct G. rarus mutants and zebrafish (Danio rerio) transgenic lines of zp genes to investigate the mechanism of egg chorion formation during evolution. After collecting G. rarus embryos at 1hour post fertilization (hpf), the egg chorion was separated from embryos, and proteins were extracted for sequencing analysis. Protein sequences were assembled sequentially, and full sequences were BLASTed against cyprinid proteins. Genes encoding these egg chorion proteins were selected as candidate genes, and based on BLAST results, we focused on zp2l2 and zp4l. We designed CRISPR/Cas9 target site in exon 1 and exon 6 of zp2l2 and zp4l to knockout genes and construct G. rarus mutants. The upstream promoter (2874 base pair, bp) of zebrafish zp3.2 gene and the coding sequence (CDS) of G. rarus zp2l2 (1137 bp) and zp4l (3009 bp) were amplified separately. The promoter of zp3.2 was firstly ligated into the vector pT2AL-ef1a-eGPF vector (containing Tol2 transposon elements) through In-fusion cloning to construct the plasmid pT2AL-zp3.2-eGPF. And then, the amplified CDS of zp2l2 and zp4l were cloned into pT2AL-zp3.2-eGPF plasmid to construct the transgenic plasmids pT2AL-zp3.2-zp2l2-eGPF and pT2AL-zp3.2-zp4l-eGPF, which were used for embryo injection. Transposase (TPase) mRNA was synthesized by in vitro transcription, mixed with constructed transgenic plasmids, and injected into zebrafish embryos to generate transgenic strains. By injecting gRNA/Cas9 protein complexes and applying a traditional three-generation screening protocol, zp2l2 and zp4l were knocked out, and stably inherited homozygous mutants were obtained in G. rarus. Additionally, using the Tol2 transposon system, we successfully created stable and inheritable transgenic zebrafish lines, Tg(zp3.2:zp2l2-eGPF) and Tg(zp3.2:zp4l-eGPF). The expression of enhanced green fluorescent protein (eGFP) was first detected at 15 days post-fertilization (dpf) in both transgenic zebrafish ovary and liver. In general, the construction of egg chorion genes zp2l2 and zp4l knocked out G. rarus mutants, as well as transgenic zebrafish lines, provide workable experimental ideas and technical routes for the mechanism research of the egg chorion formation in cyprids.

     

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