Iterative oxidation by TET1 is required for reprogramming of imprinting control regions and patterning of mouse sperm hypomethylated regions.

Ten-eleven translocation (TET) enzymes iteratively oxidize 5-methylcytosine (5mC) to generate 5-hydroxymethylcytosine (5hmC), 5-formylcytosine, and 5-carboxylcytosine to facilitate active genome demethylation. Whether these bases are required to promote replication-coupled dilution or activate base excision repair during mammalian germline reprogramming remains unresolved due to the inability to decouple TET activities. Here, we generated two mouse lines expressing catalytically inactive TET1 (Tet1-HxD) and TET1 that stalls oxidation at 5hmC (Tet1-V). Tet1 knockout and catalytic mutant primordial germ cells (PGCs) fail to erase methylation at select imprinting control regions and promoters of meiosis-associated genes, validating the requirement for the iterative oxidation of 5mC for complete germline reprogramming. TET1V and TET1HxD rescue most hypermethylation of Tet1 −/− sperm, suggesting the role of TET1 beyond its oxidative capability. We additionally identify a broader class of hypermethylated regions in Tet1 mutant mouse sperm that depend on TET oxidation for reprogramming. Our study demonstrates the link between TET1-mediated germline reprogramming and sperm methylome patterning. [Display omitted] • Non-catalytic and 5hmC-stalling TET1 mice decouple active demethylation pathways • TET1 proficiency to generate 5fC/5caC is required for germline reprogramming • Full-length TET1 catalytic mutants rescue most methylation defects of Tet1-KO sperm • TET1 catalytic activity is important for the integrity of sperm hypomethylated regions Prasasya et al. investigate the role of TET1 catalytic activity in germline reprogramming. Using catalytically inactive and 5hmC-stalling TET1 mice, they demonstrate the requirement of 5mC oxidation into 5fC/5caC for the demethylation of select imprinting control regions, meiotic gene promoters, and an additional subset of loci classified as sperm hypomethylated regions. [ABSTRACT FROM AUTHOR]