Transposon expression kinetics in Dnmt3L-/- developing testes [RNA-seq]. Mus musculus

We examined the kinetics of production of mRNAs and small RNAs derived from transposable elements during mouse spermatogenesis, in whole gonads of wildtype and DNA methylation-deficient males (Dnmt3L and Miwi2 mutants). We found that in absence of DNA methylation, transposon reactivation is not constitutive but rather occurs in a class- and development-specific manner : both the intensity of reactivation and the number of reactivated transposon classes increased as germ cells progress in meiosis. Moreover, we observed that transposon silencing before meiosis is not due to increased cleavage by the piRNA machinery. In contrast, the burst of transposon transcripts occurring at meiosis in the absence of DNA methylation serve as substrates for increased piRNA production Overall design: Six whole testis samples were analyzed, corresponding to three time points (16.5dpc, 10dpp and 20dpp) each for Dnamt3L-/- animals and control littermates. For 16.5dpc, testes from 7/8 mice were pooled per genotype. For the other stages, three mice were pooled per genotype.

我们对小鼠精子发生过程中，野生型与DNA甲基化缺陷型（Dnmt3L及Miwi2突变体）雄性个体的全性腺中，源自转座因子的信使RNA（mRNA）与小RNA的产生动力学开展了分析。
研究发现，在DNA甲基化缺失的条件下，转座子激活并非组成型发生，而是以类别及发育阶段特异性的方式进行：随着生殖细胞进入减数分裂进程，转座子激活的强度与被激活的转座子类别数量均显著提升。
此外，我们观察到减数分裂前的转座子沉默并非由piRNA（Piwi-interacting RNA）机制介导的切割增强所导致。与之相反，DNA甲基化缺失时减数分裂阶段出现的转座子转录本爆发，可作为piRNA生成增强的底物。
整体实验设计：共分析6份全睾丸样本，对应3个时间点（胚胎期16.5天（16.5dpc）、产后10天（10dpp）及产后20天（20dpp）），分别用于Dnmt3L-/-突变体动物及其同窝野生型对照。其中，16.5dpc时间点的样本为每个基因型混合7~8只小鼠的睾丸；其余阶段的样本则为每个基因型混合3只小鼠的睾丸。