ketumutant mice uncover an essential meiotic function for the ancient RNA helicase YTHDC2

Abstract

Mechanisms regulating mammalian meiotic progression are poorly understood. Here we identify mouse YTHDC2 as a critical component. A screen yielded a sterile mutant, "ketu", caused by a Ythdc2 missense mutation. Mutant germ cells enter meiosis but proceed prematurely to aberrant metaphase and apoptosis, and display defects in transitioning from spermatogonial to meiotic gene expression programs. ketu phenocopies mutants lacking MEIOC, a YTHDC2 partner. Consistent with roles in post-transcriptional regulation, YTHDC2 is cytoplasmic, has 3ʹ→5ʹ RNA helicase activity in vitro, and has similarity within its YTH domain to an N 6 -methyladenosine recognition pocket. Orthologs are present throughout metazoans, but are diverged in nematodes and, more dramatically, Drosophilidae, where Bgcn is descended from a Ythdc2 gene duplication. We also uncover similarity between MEIOC and Bam, a Bgcn partner unique to schizophoran flies. We propose that regulation of gene expression by YTHDC2-MEIOC is an evolutionarily ancient strategy for controlling the germline transition into meiosis. Version 2: The following experimental changes were incorporated:• RNA-seq analyses of wild-type and Ythdc2 mutant testes at 8, 9, and 10 dpp (i.e., during the germline transition into meiosis).• Purification and characterization of recombinant YTHDC2 protein, demonstrating RNA helicase activity and effect of the ketu mutation.• Expanded histological and cytological analyses (DMC1-staining; PAS-staining and TUNEL assay at 8 dpp; further pH3 and tubulin staining along with SYCP3 staining in abnormal metaphases to evaluate premature metaphase entry; BrdU incorporation to evaluate premeiotic DNA replication; and more complete evaluation of persistent CCNA2 expression), including quantification of stainings at multiple ages (pH3, α-tubulin, BrdU, SYCP3, and CCNA2 stainings as well as TUNEL assay). Cem Meydan, Nathalie Lailler, Christopher E. Mason, and Christopher D. Lima were added as coauthors.

Readers of the m6A epitranscriptomic code

“…Consistently with its high expression in mammalian germlines [55][56][57], YTHDC2 is required for proper male and female fertility. Ythdc2-deficient mice are viable but infertile with males and females having smaller testes and ovaries respectively.…”

YTHDC2 Promotes the Apoptosis of Colorectal Cancer Cells Through the p38MAPK Signaling Pathway

“…Many studies have indicated YTHDC2 to be crucial for fertility in both male and female mice, with particular importance in spermatogenesis [21][22][23][24] . Other studies have indicated that YTHDC2 may be related to autism spectrum disorder [25] , hepatitis C [21] , pancreatic adenocarcinoma [26] , and CRC [27] . The present research demonstrates that the expression of YTHDC2 is negatively correlated with overall survival and tumor stage in CRC.…”

Functions of N6-methyladenosine and its role in cancer

“…YTHDC2 is an RNA-induced ATPase with a 3′ -to-5′ RNA helicase activity [97]. Germ cells down-regulated YTHDC2 enter meiosis but process prematurely to abnormal metaphase and apoptosis [98,99].…”