Fam60a is a component of the mSin3A-HDAC transcriptional corepressor complex and inhibits Tet-mediated DNA demethylation

Fam60a was identified as a highly expressed gene of unknown function in mouse embryonic stem cells. We have examined the role of Fam60a in mouse development. Most Fam60a mutant embryos manifest hypoplasia of visceral organs and die in utero. Fam60a interacts with components of the mSin3A-HDAC transcriptional corepressor complex and is recruited to the promoter regions of a subset of genes throughout the genome. Genome-wide gene expression analysis revealed that Fam60a target genes are either up- or down-regulated in Fam60a mutant embryos. In cultured cells, Fam60a inhibited the global conversion of 5-methylcytosine to 5-hydroxymethylcytosine mediated by TET1. Furthermore, bisulfite sequencing analysis of Fam60a target gene promoters showed that the DNA methylation level of Adhfe1 is maintained at embryonic day (E) 7.5 but is markedly reduced at E9.5 in Fam60a mutant embryos, suggesting that DNA demethylation is enhanced in the mutant. Our data suggest that Fam60a is a component of the mSin3A-HDAC complex and is required for proper embryogenesis, at least in part as a result of its inhibition of Tet-mediated DNA demethylation at specific gene promoters.Fam60a是在小鼠胚胎干细胞中被鉴定出的高表达、功能未知的基因。本研究针对Fam60a在小鼠发育过程中的功能展开了探究。多数Fam60a基因突变的胚胎表现出内脏器官发育不全，并于子宫内死亡。Fam60a可与mSin3A-HDAC转录共抑制复合物（mSin3A-HDAC transcriptional corepressor complex）的组分相互结合，并被招募至全基因组中部分基因的启动子区域。全基因组基因表达分析显示，在Fam60a基因突变的胚胎中，Fam60a的靶基因呈现上调或下调表达。在培养细胞中，Fam60a可抑制由TET1介导的5-甲基胞嘧啶(5-methylcytosine)向5-羟甲基胞嘧啶(5-hydroxymethylcytosine)的全基因组转化。此外，针对Fam60a靶基因启动子区域的亚硫酸氢盐测序分析显示，在Fam60a基因突变的胚胎中，Adhfe1的DNA甲基化水平在胚胎发育第7.5天（E7.5）仍维持稳定，但在第9.5天（E9.5）显著降低，提示突变体中DNA去甲基化过程被增强。本研究数据表明，Fam60a是mSin3A-HDAC复合物的组分之一，且对正常胚胎发育不可或缺，其功能至少部分通过抑制特定基因启动子区域的TET1介导的DNA去甲基化来实现。