O'Neil E V, Dupont S M, Capel B
Department of Cell Biology, Duke University School of Medicine, Durham NC 27710.
bioRxiv. 2025 Mar 4:2025.02.28.640455. doi: 10.1101/2025.02.28.640455.
The bipotential gonad is the precursor organ to both the ovary and testis and develops as part of the embryonic urogenital system. In mice, gonadogenesis initiates around embryonic day 9.5 (E9.5), when coelomic epithelial (CE) cells overlaying the mesonephric ducts proliferate and acquire the competence to differentiate into the two main cell types of the embryonic gonad, the pre-supporting cells and interstitial cell lineages. While some transcription factors that drive gonadal cell fate are known, HLH factors have not been investigated in this capacity. In the present study, we found that HLH binding sites are highly represented upstream of gonadal genes. We investigated the HLH factor Transcription Factor 4 (TCF4) which is expressed in the CE and GATA4+ somatic cells in both sexes prior to sex determination. TCF4 is maintained in ovarian pre-supporting cells and interstitial cells of both sexes but is silenced specifically in male pre-supporting cells. To characterize TCF4's role in gonad differentiation we acquired a mutant mouse model that lacks the TCF4 DNA-binding domain and assessed morphology of the gonads at E15.5. While mutants develop gonads, we observed sex-specific effects on the gonads. Relative to wildtype littermates, SOX9 expression was higher in the Sertoli cells of XY mutant testes, while FOXL2 and NR2F2 were reduced in the supporting and interstitial cell lineages of XX mutant ovaries, respectively. Furthermore, the supporting: interstitial cell ratio was altered in XX ovaries. These effects may occur downstream of changes to epigenetic programming or gene expression in somatic gonadal cells in mutant mice, as TCF4 binds the Mediator complex, RNA polymerase holoenzyme, and chromatin remodelers in early somatic cells. We hypothesize that TCF4 drives a gonadal program that advances female fate but is specifically silenced in male supporting cells as these pathways diverge.
双潜能性腺是卵巢和睾丸的前体器官，作为胚胎泌尿生殖系统的一部分发育而成。在小鼠中，性腺发生始于胚胎第9.5天（E9.5）左右，此时覆盖中肾管的体腔上皮（CE）细胞增殖，并获得分化为胚胎性腺两种主要细胞类型（前支持细胞和间质细胞谱系）的能力。虽然已知一些驱动性腺细胞命运的转录因子，但尚未对HLH因子在此方面进行研究。在本研究中，我们发现HLH结合位点在性腺基因上游高度富集。我们研究了HLH因子转录因子4（TCF4），它在性别决定之前在两性的CE和GATA4 + 体细胞中表达。TCF4在两性的卵巢前支持细胞和间质细胞中维持表达，但在雄性前支持细胞中特异性沉默。为了表征TCF4在性腺分化中的作用，我们获得了一个缺乏TCF4 DNA结合结构域的突变小鼠模型，并在E15.5评估性腺形态。虽然突变体发育出性腺，但我们观察到性腺有性别特异性影响。相对于野生型同窝仔，XY突变体睾丸的支持细胞中SOX9表达较高，而XX突变体卵巢的支持细胞和间质细胞谱系中FOXL2和NR2F2分别减少。此外，XX卵巢中的支持细胞：间质细胞比例发生改变。这些影响可能发生在突变小鼠性腺体细胞中表观遗传编程或基因表达变化的下游，因为TCF4在早期体细胞中与中介复合物、RNA聚合酶全酶和染色质重塑因子结合。我们假设TCF4驱动一个性腺程序，该程序促进雌性命运，但在雄性支持细胞中随着这些途径的分化而特异性沉默。
