Dev105130 1..12

The ability of adult stem cells to reside in a quiescent state is crucial for preventing premature exhaustion of the stem cell pool. However, the intrinsic epigenetic factors that regulate spermatogonial stem cell quiescenceare largelyunknown.Here,we investigate inmicehowDNA methyltransferase 3-like (DNMT3L), an epigenetic regulator important for interpreting chromatin context and facilitating de novo DNA methylation, sustains the long-term male germ cell pool. We demonstrated that stem cell-enriched THY1 spermatogonial stem/ progenitor cells (SPCs) constituted a DNMT3L-expressing population in postnatal testes. DNMT3L influenced the stability of promyelocytic leukemia zinc finger (PLZF), potentially by downregulatingCdk2/CDK2 expression, which sequestered CDK2-mediated PLZF degradation. Reduced PLZF inDnmt3l KOTHY1 cells released its antagonist, Sallike protein 4A (SALL4A), which is associated with overactivated ERK and AKT signaling cascades. Furthermore, DNMT3L was required to suppress thecell proliferation-promoting factorSALL4B inTHY1SPCs and to prevent premature stem cell exhaustion. Our results indicate that DNMT3L is required todelicatelybalance the cyclingandquiescenceof SPCs. These findings reveal a novel role for DNMT3L in modulating postnatal SPC cell fate decisions.