Transposon-derived piRNA production in pre-natal and post-natal stages, in Dnmt3L and Miwi2 mutant tetses [small 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. Dnmt3L mutant animals were analyzed at 16.5dpc and 10dpp, and Miwi2 mutant animals at 10dpp, in parallel with control littermates. For 16.5dpc, testes from 7/8 mice were pooled per genotype. For 10dpp, three mice were pooled per genotype.