The XRN1-regulated RNA helicase activity of YTHDC2 ensures mouse fertility independently of m6A recognition

The functional consequence of N-6-methyladenosine (m(6)A) RNA modification is mediated by reader proteins of the YTH family. YTH domain-containing 2 (YTHDC2) is essential for mammalian fertility, but its molecular function is poorly understood. Here, we identify U-rich motifs as binding sites of YTHDC2 on 3' UTRs of mouse testicular RNA targets. Although its YTH domain is an m6A-binder in vitro, the YTH point mutant mice are fertile. Significantly, the loss of its 3'-> 5' RNA helicase activity causes mouse infertility, with the catalytic-dead mutation being dominant negative. Biochemical studies reveal that the weak helicase activity of YTHDC2 is enhanced by its interaction with the 5'-> 3' exoribonuclease XRN1. Single-cell transcriptomics indicate that Ythdc2 mutant mitotic germ cells transition into meiosis but accumulate a transcriptome with mixed mitotic/meiotic identity that fail to progress further into meiosis. Finally, our demonstration that ythdc2 mutant zebrafish are infertile highlights its conserved role in animal germ cell development.

Automated summary

The YTHDC2 protein plays a crucial role in mammalian fertility by binding to specific sites on the 3' UTRs of mouse testicular RNA targets. The loss of its 3'-> 5' RNA helicase activity leads to infertility in mice. Furthermore, its weak helicase activity is enhanced through interaction with the exoribonuclease XRN1. Studies on ythdc2 mutant zebrafish demonstrate its conserved role in animal germ cell development.