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Abstract：
Some X-linked genes necessary for spermiogenesis are specifically activated in the postmeiotic germ cells. However, the regulatory mechanism about this activation is not clearly understood. Here, we examined the potential mechanism controlling the transcriptional activation of the mouse testis specific gene A8 (Tsga8) gene in round spermatids. We observed that the Tsga8 expression was negatively correlated with the methylation level of the CpG sites in its core promoter. During spermatogenesis, the Tsga8 promoter was methylated in spermatogonia, and then demethylated in spermatocytes. The demethylation status of Tsga8 promoter was maintained through the postmeiotic germ cells, providing a potentially active chromatin for Tsga8 transcription. In vitro investigation showed that the E12 and Spz1 transcription factors can enhance the Tsga8 promoter activity by binding to the unmethylated E-box motif within the Tsga8 promoter. Additionally, the core Tsga8 promoter drove green fluorescent protein (GFP) expression in the germ cells of Tsga8-GFP transgenic mice, and the GFP expression pattern was similar to that of endogenous Tsga8. Moreover, the DNA methylation profile of the Tsga8-promoter-driven transgene was consistent with that of the endogenous Tsga8 promoter, indicating the existence of a similar epigenetic modification for the Tsga8 promoter to ensure its spatiotemporal expression in vivo. Taken together, this study reports the details of a regulatory mechanism that includes DNA methylation and transcription factors to mediate the postmeiotic expression of an X-linked gene.
摘要：
精子发生所必需的一些X连锁基因在减数分裂后生殖细胞中被特异性激活。然而,关于这种激活的调节机制尚不清楚。这里,我们研究了控制圆形精子细胞中小鼠睾丸特异性基因A8（Tsga8）基因转录激活的潜在机制。我们观察到Tsga8的表达与其核心启动子中CpG位点的甲基化水平呈负相关。在精子发生过程中,Tsga8启动子在精原细胞中甲基化，然后在精母细胞中去甲基化。通过减数分裂后生殖细胞维持Tsga8启动子的去甲基化状态,为Tsga8转录提供潜在的活性染色质。体外研究表明，E12和Spz1转录因子可以通过与Tsga8启动子内的未甲基化E-box基序结合来增强Tsga8启动子的活性。此外,核心Tsga8启动子驱动绿色荧光蛋白（GFP）在Tsga8-GFP转基因小鼠的生殖细胞中表达，GFP表达模式与内源性Tsga8相似。此外，Tsga8启动子驱动的转基因的DNA甲基化谱与内源性Tsga8启动子一致，表明Tsga8启动子存在类似的表观遗传修饰，以确保其在体内的时空表达。一起来看,这项研究报道了包括DNA甲基化和转录因子介导X连锁基因减数分裂后表达的调控机制的细节。
