利用iCaspase9特异性诱导鸡原始生殖细胞消除的研究

Specific induction of ablation of chicken primordial germ cells using iCaspase9

  • 摘要: 【目的】制备在生殖细胞特异表达iCaspase9的鸡原始生殖细胞系(PGCs),提升外源性PGCs的生殖传递效率,为生产诱导不育的雄性或雌性受体鸡胚打下基础。【方法】利用piggyBac转座子将iCaspase9片段整合到鸡基因组中,构建稳定转染iCaspase9片段的CAG-iCaspase9-mCherry DF-1细胞系,通过荧光微显镜观察鉴定其在iCaspase9系统诱导底物B/B二聚化配体作用下的细胞消除效果;再利用CRISPR/Cas9技术将iCaspase9片段定点插入DAZL基因第11外显子之后构建Dazl-iCaspase9-EGFP PGCs,经iCaspase9片段插入鉴定和PGCs生殖特性鉴定后,通过荧光微显镜观察鉴定其在B/B二聚化配体诱导下的消除效果。【结果】成功建立的CAG-iCaspase9-mCherry DF-1细胞系与野生型DF-1细胞(WT DF-1)的生长增殖无显著差异(P>0.05,下同);CCK-8法测定发现,0.25~5.00 nmol/L B/B二聚化配体对WT DF-1细胞生长数量无显著影响,但CAG-iCaspase9-mCherry DF-1细胞在添加B/B二聚化配体后,细胞数量较空白对照组极显著降低(P<0.01,下同),且失去正常的细胞形态,逐渐变圆甚至凋亡。成功建立的DAZL-iCaspase9-EGFP PGCs仍特异性高表达CvhNanogPouVDAZLCdhDdx4等生殖细胞相关基因,在蛋白水平上也能鉴定出DAZL、SSEA1和CVH等蛋白,说明插入iCaspse9片段后并没有改变生PGCs的殖细胞特异性;在0.25 nmol/L B/B二聚化配体诱导作用下,DAZL-iCaspae9-EGFP PGCs数量显著减少,几乎全部消除,说明iCaspase9系统可诱导细胞凋亡而有效消除内源性PGCs。【结论】利用iCaspase9系统构建获得的DAZL-iCaspase9-EGFP PGCs在不改变其生殖细胞特性的同时,可在B/B二聚化配体诱导下有效消除内源性PGCs,为建立高效鸡种质资源恢复和基因编辑鸡制备等研究提供无内源性PGCs的受体鸡胚。

     

    Abstract: 【Objective】The purpose of the study was to prepare chicken germ cell lines that express iCaspase9 specifically in primordial germ cells(PGCs),to improve the reproductive transmission efficiency of exogenous PGCs,and to lay the foundation for the production of male or female receptor chicken embryos that induce infertility.【Method】The iCaspase9 fragment was integrated into the chicken genome using the piggyBac transposon,and a stable CAG-iCaspase9mCherry DF-1 cell line transfected with the iCaspase9 fragment was constructed. Its cell ablation effect under the induction of substrate B/B homodimerizer by the iCaspase9 system was identified by fluorescence microscope. Using CRISPR/Cas9 technology,the iCaspase9 fragment was inserted into the 11th exon of the DAZL gene to construct Dazl-iCaspase9EGFP PGCs. After identification of iCaspase9 fragment insertion and PGC reproductive characteristics,its ablation effect under B/B homodimerizer induction was identified by fluorescence microscope.【Result】There was no significant difference in growth and proliferation between the successfully established CAG-iCaspase9-mCherry DF-1 cell line and wildtype DF-1 cells(WT DF-1)(P>0.05,the same below). CCK-8 assay revealed that 0.25-5.00 nmol/L B/B homodimerizer had no significant effect on the growth of WT DF-1 cells. However,after adding B/B homodimerizer to CAG-iCaspase9-mCherry DF-1 cells,the number of cells extremely significantly decreased compared to the blank control group(P<0.01, the same below),and normal cell morphology was lost,which gradually becoming round or even apoptotic. The successfully established DAZL-iCaspase9-EGFP PGCs still specifically and highly expressed germ cell related genes such as Cvh,Nanog,PouV,DAZL,Cdh,and Ddx4. Proteins such as DAZL,SSEA1,and CVH could also be identified at the protein level,indicating that the insertion of iCaspase9 fragments did not alter the germ cell specificity of PGCs. Under the induction effect of 0.25 nmol/L B/B homodimerizer,the number of DAZL-iCaspae9-EGFP PGCs significantly decreased and almost all of them were eliminated,indicating that the iCaspase9 system can induce cell apoptosis and effectively eliminate endogenous PGCs.【Conclusion】The DAZL-iCaspase9-EGFP PGCs constructed using the iCaspase9 system can significantly eliminate endogenous PGCs under B/B homodimerizer induction without altering their germ cell characteristics,which provides a receptor chicken embryo without endogenous PGCs for establishing efficient chicken germplasm resource recovery and gene editing chicken preparation research.

     

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