DMRT6 coordinates the transition between mitotic and meiotic developmental programs during mammalian spermatogenesis

In mammals, a key transition in spermatogenesis is the exit from spermatogonial differentiation and mitotic proliferation and the entry into spermatocyte differentiation and meiosis. Although several genes that regulate this transition have been identified, how it is controlled and coordinated remains poorly understood. Here we examine the role in male gametogenesis of the Doublesex-related gene Dmrt6 (Dmrtb1) and find that Dmrt6 plays a critical role in directing germ cells through the mitotic to meiotic germ cell transition. DMRT6 protein is expressed in late mitotic spermatogonia. In mice of the C57BL/6J strain a null mutation in Dmrt6 disrupts spermatogonial differentiation, causing expression in inappropriate cell types of spermatogonial differentiation factors including SOHLH1, SOHLH2 and DMRT1 and the meiotic initiation factor STRA8 and causing most late spermatogonia to undergo apoptosis. In mice of the 129Sv background, most Dmrt6 mutant spermatogonia can complete differentiation and enter meiosis, but they show defects in chromosome pairing, establishment of the XY body, and processing of recombination foci, and mainly arrest in mid-pachynema. mRNA profiling of Dmrt6 mutant testes together with DMRT6 ChIP-seq suggest that DMRT6 represses genes involved in spermatogonial differentiation and activates genes required for meiotic prophase. Our results indicate that Dmrt6 plays a key role in coordinating the transition in gametogenic programs from spermatogonial differentiation and mitosis to spermatocyte development and meiosis. Six samples for RNA-Seq with three biological replicates in each group. Two samples for ChIP-Seq (one input and one ChIP).在哺乳动物的精子发生过程中，一个关键转变是精原细胞分化与有丝分裂增殖的退出，以及进入精母细胞分化和减数分裂阶段。尽管目前已鉴定出若干调控该转变的基因，但其具体的调控与协同机制仍未被充分阐明。本研究探究了Doublesex相关基因Dmrt6（Dmrtb1）在雄性配子发生中的功能，发现其在引导生殖细胞完成有丝分裂向减数分裂的转变过程中发挥关键作用。DMRT6蛋白在晚期有丝分裂精原细胞中表达。在C57BL/6J品系小鼠中，Dmrt6的功能缺失突变会破坏精原细胞分化，导致精原细胞分化因子（包括SOHLH1、SOHLH2与DMRT1）以及减数分裂起始因子STRA8在异常细胞类型中表达，并使多数晚期精原细胞发生凋亡。在129Sv背景的小鼠中，多数Dmrt6突变型精原细胞可完成分化并进入减数分裂，但它们存在染色体配对、XY小体建立以及重组焦点加工的缺陷，且主要在粗线期中期发生发育阻滞。对Dmrt6突变型睾丸的mRNA转录组分析结合DMRT6的染色质免疫共沉淀测序（ChIP-seq）实验结果表明，DMRT6可抑制精原细胞分化相关基因的表达，并激活减数分裂前期所需的基因。本研究结果显示，Dmrt6在协调配子发生程序从精原细胞分化与有丝分裂向精母细胞发育及减数分裂的转变中扮演核心角色。本研究设置两组各3次生物学重复，共6个RNA测序（RNA-Seq）样本；另有2个ChIP-seq样本，其中1个为输入对照，1个为免疫沉淀样本。