BACKGROUND Caenorhabditis elegans seam cells serve as a good model to understand how genes and signaling pathways interact to control asymmetric cell fates. The stage-specific pattern of seam cell division is coordinated by a genetic network that includes WNT asymmetry pathway components WRM-1, LIT-1, and POP-1, as well as heterochronic microRNAs (miRNAs) and their downstream targets. Mutations in pry-1, a negative regulator of WNT signaling that belongs to the Axin family, were shown to cause seam cell defects; however, the mechanism of PRY-1 action and its interactions with miRNAs remain unclear. RESULTS We found that pry-1 mutants in C. elegans exhibit seam cell, cuticle, and alae defects. To examine this further, a miRNA transcriptome analysis was carried out, which showed that let-7 (miR-48, miR-84, miR-241) and lin-4 (lin-4, miR-237) family members were upregulated in the absence of pry-1 function. Similar phenotypes and patterns of miRNA overexpression were also observed in C. briggsae pry-1 mutants, a species that is closely related to C. elegans. RNA interference-mediated silencing of wrm-1 and lit-1 in the C. elegans pry-1 mutants rescued the seam cell defect, whereas pop-1 silencing enhanced the phenotype, suggesting that all three proteins are likely important for PRY-1 function in seam cells. We also found that these miRNAs were overexpressed in pop-1 hypomorphic animals, suggesting that PRY-1 may be required for POP-1-mediated miRNA suppression. Analysis of the let-7 and lin-4-family heterochronic targets, lin-28 and hbl-1, showed that both genes were significantly downregulated in pry-1 mutants, and furthermore, lin-28 silencing reduced the number of seam cells in mutant animals. CONCLUSIONS Our results show that PRY-1 plays a conserved role to maintain normal expression of heterochronic miRNAs in nematodes. Furthermore, we demonstrated that PRY-1 acts upstream of the WNT asymmetry pathway components WRM-1, LIT-1, and POP-1, and miRNA target genes in seam cell development.

中文翻译：

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PRY-1 / Axin在异时miRNA介导的接缝细胞发育中的作用。

背景技术秀丽隐杆线虫接缝细胞是了解基因和信号传导途径如何相互作用以控制不对称细胞命运的良好模型。接缝细胞分裂的特定阶段模式由一个遗传网络协调，该遗传网络包括WNT不对称途径成分WRM-1，LIT-1和POP-1，以及异时微RNA（miRNA）及其下游靶标。pry-1（属于Axin家族的WNT信号的负调节剂）中的突变被证明会引起接缝细胞缺陷。然而，PRY-1的作用机理及其与miRNA的相互作用尚不清楚。结果我们发现秀丽隐杆线虫中的pry-1突变体显示出接缝细胞，表皮和alae缺陷。为了进一步检查，进行了miRNA转录组分析，结果显示let-7（miR-48，miR-84，miR-241）和lin-4（lin-4，miR-237）家庭成员在不存在pry-1功能的情况下上调。在Briggsae pry-1突变体（与秀丽隐杆线虫密切相关的物种）中也观察到了类似的miRNA表型和miRNA过表达模式。秀丽隐杆线虫pry-1突变体中wrm-1和lit-1的RNA干扰介导的沉默拯救了接缝细胞缺陷，而pop-1沉默增强了表型，表明这三种蛋白可能对PRY-1的功能很重要在接缝细胞中。我们还发现，这些miRNA在pop-1亚型动物中过表达，这表明POP-1介导的miRNA抑制可能需要PRY-1。对let-7和lin-4家族异质性靶标lin-28和hbl-1的分析表明，这两个基因在pry-1突变体中均显着下调，此外，lin-28沉默减少了突变动物中接缝细胞的数量。结论我们的结果表明，PRY-1在线虫中可以保持异时性miRNA的正常表达。此外，我们证明了PRY-1在WNT不对称途径组分WRM-1，LIT-1和POP-1以及上游miRNA靶基因在接缝细胞发育中起作用。