Expression data from mir-35-41(nDf50) mutant embryos grown at 20 degrees, compared to wild type

Gene expression in early animal embryogenesis is in large part controlled post-transcriptionally. Maternally-contributed microRNAs may therefore play important roles in early development. We have elucidated a major biological role of the nematode mir-35 family of maternally-contributed, essential microRNAs. We show that this microRNA family regulates the sex determination pathway at multiple levels, acting both upstream and downstream of her-1 to prevent aberrantly activated male developmental programs in hermaphrodite embryos. The predicted target genes that act downstream of the mir-35 family in this process, sup-26 and nhl-2, both encode RNA binding proteins, thus delineating a previously unknown post-transcriptional regulatory subnetwork within the well-studied sex determination pathway of C. elegans. Repression of nhl-2 by the mir-35 family is not only required for proper sex determination but also for viability, showing that a single microRNA target site can be essential. Since sex determination in C. elegans requires zygotic gene expression to read the sex chromosome karyotype, early embryos must remain gender-nave; our findings show that the mir-35 family microRNAs act in the early embryo to function as a developmental timer that preserves navet and prevents premature deleterious developmental decisions. The mir-35 family of microRNAs is essential for development. The mir-35-41(nDf50) allele deleted 7 of 8 mir-35 family members, and presents a hypomorphic phenotype in which embryonic lethality is temperature sensitive. To characterize the molecular phenotype associated with loss of mir-35 family function, we profiled gene expression in mir-35-41(nDf50) mutant embryos at both permissive (20) and restrictive (25) temperatures. (Refer to A microRNA family exerts maternal control on sex determination in C. elegans)动物早期胚胎发生过程中的基因表达，在很大程度上受转录后调控机制支配。因此，母体来源的微小RNA（microRNA）可能在早期发育中发挥关键作用。我们阐明了线虫mir-35家族这一母体贡献的必需微小RNA家族的主要生物学功能。研究发现，该微小RNA家族可在多个层面调控性别决定通路，分别作用于her-1的上游与下游，以阻止雌雄同体胚胎中异常激活的雄性发育程序。该通路中mir-35家族下游的预测靶基因sup-26与nhl-2均编码RNA结合蛋白，由此在研究较为透彻的秀丽隐杆线虫（C. elegans）性别决定通路中，勾勒出一条此前未被发现的转录后调控子网。mir-35家族对nhl-2的抑制不仅是正常性别决定所必需的，同时也对个体存活至关重要，这表明单个微小RNA靶位点即可发挥必需功能。由于秀丽隐杆线虫的性别决定需要合子基因表达来读取性染色体核型，早期胚胎必须维持性别未分化状态；我们的研究结果显示，mir-35家族微小RNA可在早期胚胎中充当发育计时器，维持未分化状态并防止过早出现有害的发育决策。mir-35家族微小RNA对胚胎发育不可或缺。mir-35-41(nDf50)等位基因缺失了该家族8个成员中的7个，表现出减效表型，其胚胎致死性具有温度敏感性。为了表征mir-35家族功能缺失对应的分子表型，我们在允许温度（20℃）与限制性温度（25℃）下，对mir-35-41(nDf50)突变体胚胎的基因表达谱进行了分析。（参阅《A microRNA family exerts maternal control on sex determination in C. elegans》）