Gene regulatory divergence in spermatogenesis between mouse and opossum

Mammalian spermatogenesis is a highly stereotyped and conserved developmental process that is essential for fitness. At the same time, gene expression in spermatogenic cells is rapidly evolving. This combination of features has been suggested to drive rapid fixation of new gene expression patterns. Using a high-resolution dataset comprising bulk and single-cell data from juvenile and adult testes of the opossum Monodelphis domestica, a model marsupial, we define the developmental timing of the spermatogenic first wave in opossum and delineate conserved and divergent gene expression programs across the placental-marsupial split by comparison to equivalent data from mouse, a model placental mammal. Epigenomic data confirmed divergent regulation at the level of transcription, and comparison to data from four additional amniote species identified hundreds of genes with evidence of rapid fixation of expression. This gene set encompasses known and previously undescribed regulators of spermatogenic development.哺乳动物精子发生（Mammalian spermatogenesis）是一种高度刻板且保守的发育过程，对生物体的适合度至关重要。与此同时，生精细胞（spermatogenic cells）中的基因表达处于快速进化状态。这种双重特征被认为推动了新基因表达模式的快速固定。本研究采用一套高分辨率数据集，涵盖模式有袋类（marsupial）动物灰短尾负鼠（Monodelphis domestica）幼龄与成年个体睾丸的批量测序数据（bulk data）与单细胞测序数据（single-cell data），明确了该物种精子发生首波的发育时序；通过与模式胎盘类哺乳动物小鼠的对应数据集进行比较，勾勒出胎盘类-有袋类分化（placental-marsupial split）节点处保守与趋异的基因表达调控程序。表观基因组数据（Epigenomic data）证实了转录层面的趋异调控；通过与另外4种羊膜动物（amniote species）的数据集开展比较，本研究鉴定出数百个存在表达快速固定迹象的基因。该基因集涵盖了已知的以及此前未被发现的精子发生发育调控因子。