De novo DNA methylation (DNAme) in mammalian germ cells is dependent on DNMT3A and DNMT3L. However, oocytes and spermatozoa show distinct patterns of DNAme. In mouse oocytes, de novo DNAme requires the lysine methyltransferase (KMTase) SETD2, which deposits H3K36me3. We show here that SETD2 is dispensable for de novo DNAme in the male germline. Instead, the lysine methyltransferase NSD1, which broadly deposits H3K36me2 in euchromatic regions, plays a critical role in de novo DNAme in prospermatogonia, including at imprinted genes. However, males deficient in germline NSD1 show a more severe defect in spermatogenesis than Dnmt3l^−/− males. Notably, unlike DNMT3L, NSD1 safeguards a subset of genes against H3K27me3-associated transcriptional silencing. In contrast, H3K36me2 in oocytes is predominantly dependent on SETD2 and coincides with H3K36me3. Furthermore, females with NSD1-deficient oocytes are fertile. Thus, the sexually dimorphic pattern of DNAme in mature mouse gametes is orchestrated by distinct profiles of H3K36 methylation.

哺乳动物生殖细胞中的从头 DNA 甲基化 (DNAme) 依赖于 DNMT3A 和 DNMT3L。然而，卵母细胞和精子显示出不同的 DNAme 模式。在小鼠卵母细胞中，从头 DNAme 需要赖氨酸甲基转移酶 (KMTase) SETD2，它会沉积 H3K36me3。我们在这里表明，SETD2 对于雄性生殖系中的从头 DNAme 是可有可无的。相反，赖氨酸甲基转移酶 NSD1 在常染色质区域广泛沉积 H3K36me2，在原精原细胞的从头 DNAme 中起关键作用，包括印迹基因。然而，缺乏生殖系 NSD1 的男性在精子发生方面表现出比Dnmt3l更严重的缺陷^-/-男性。值得注意的是，与 DNMT3L 不同，NSD1 保护基因子集免受 H3K27me3 相关的转录沉默。相比之下，卵母细胞中的 H3K36me2 主要依赖于 SETD2，并且与 H3K36me3 一致。此外，具有 NSD1 缺陷卵母细胞的雌性具有生育能力。因此，成熟小鼠配子中 DNAme 的性二态模式是由 H3K36 甲基化的不同特征所协调的。