FTO Knockout Causes Chromosome Instability and G2/M Arrest in Mouse GC-1 Cells

N(6)-methyladenosine (m(6)A) is the most abundant modification on eukaryotic mRNA. m(6)A plays important roles in the regulation of post-transcriptional RNA splicing, translation, and degradation. Increasing studies have uncovered the significance of m(6)A in various biological processes such as stem cell fate determination, carcinogenesis, adipogenesis, stress response, etc, which put forwards a novel conception called epitranscriptome. However, functions of the fat mass and obesity-associated protein (FTO), the first characterized m(6)A demethylase, in spermatogenesis remains obscure. Here we reported that depletion of FTO by CRISPR/Cas9 induces chromosome instability and G2/M arrest in mouse spermatogonia, which was partially rescued by expression of wild type FTO but not demethylase inactivated FTO. FTO depletion significantly decreased the expression of mitotic checkpoint complex and G2/M regulators. We further demonstrated that the m(6)A modification on Mad1, Mad2, Bub1b, Cdk1, and Ccnb2 were directly targeted by FTO. Therefore, FTO regulates cell cycle and mitosis checkpoint in spermatogonia because of its m(6)A demethylase activity. The findings give novel insights into the role of RNA methylation in spermatogenesis.