MIWI N-terminal RG motif promotes efficient pachytene piRNA production and spermatogenesis independent of LINE1 transposon silencing

by Chao Wei, Jiongjie Jing, Xiaoyuan Yan, Jeffrey M. Mann, Ruirong Geng, Huirong Xie, Elena Y. Demireva, Rex A. Hess, Deqiang Ding, Chen Chen PIWI proteins and their associated piRNAs act to silence transposons and promote gametogenesis. Murine PIWI proteins MIWI, MILI, and MIWI2 have multiple arginine and glycine (RG)-rich motifs at their N-terminal domains. Despite being known as docking sites for the TDRD family proteins, thein vivo regulatory roles for these RG motifs in directing PIWI in piRNA biogenesis and spermatogenesis remain elusive. To investigate the functional significance of RG motifs in mammalian PIWI proteinsin vivo, we genetically engineered an arginine to lysine (RK) point mutation of a conserved N-terminal RG motif in MIWI in mice. We show that this tiny MIWI RG motif is indispensable for piRNA biogenesis and male fertility. The RK mutation in the RG motif disrupts MIWI-TDRKH interaction and impairs enrichment of MIWI to the intermitochondrial cement (IMC) for efficient piRNA production. Despite significant overall piRNA level reduction, piRNA trimming and maturation are not affected by the RK mutation. Consequently,MiwiRK mutant mice show chromatoid body malformation, spermatogenic arrest, and male sterility. Surprisingly, LINE1 transposons are effectively silenced inMiwiRK mutant mice, indicating a LINE1-independent cause of germ cell arrest distinctive fromMiwi knockout mice. These findings reveal a crucial function of the RG motif in directing PIWI pr...
Source: PLoS Genetics - Category: Genetics & Stem Cells Authors: Source Type: research