Molecular mechanism of sex determination and its disease

在人类中，就像在其他哺乳动物中一样，性别决定由一个被称为睾丸决定因子TDF的显性开关控制。SRY基因被认为是TDF，它编码一个转录因子，其中一个HMG盒作为DNA结合域。已在15%的人类XY性反转病例中发现SRY HMG盒突变。将小鼠SRY基因(Sry)导入XX雌性小鼠诱导睾丸分化和随后的雄性发育。然而，对SRY的转录调控机制知之甚少。WT1突变在Denys-Drash综合征(DDS)合并泌尿生殖系统畸形的患者中经常被观察到，在对WT1相关蛋白进行分析时，我们发现WT1与Sox30结合，Sox30编码一个带有一个HMG盒的新的转录因子。进一步分析表明，WT1与其HMG盒结合。这一观察结果促使我们分析了WT1和SRY之间的相互作用，这两种基因都在早期性腺的体细胞中表达。我们的研究结果表明：1)WT1在体外和培养细胞中与SRY结合。ii)WT1和SRY协同激活含有SRY结合序列的启动子和SRY启动子的转录。iii)在DDS中发现的WT1突变体没有表现出这种活性。iv)WT1以SRY依赖的方式被招募到SRY结合序列上，而DDS突变体的招募显著减少。这些观察表明WT1和SRY的相互作用在早期性腺发育和疾病中起着重要作用。最近，我们建立了同时表达WT1和SRY的细胞系。我们目前正在分析该细胞系的表达谱，这将揭示WT1和SRY调控的靶基因。

In humans, as in other mammals, sex determination is controlled by a dominant switch termed TDF for Testis Determining Factor. The SRY gene is thought to be the TDF, which encodes a transcription factor with one HMG box as a DNA binding domain. Mutations in the SRY HMG box have been identified in 15% cases of XY sex reversal in humans. Introduction of mouse SRY gene (Sry) into XX female mice induced testis differentiation and subsequent male development. However, little is known about mechanism of transcriptional regulation by SRY. WT1 mutations have frequently been observed in Denys-Drash syndrome (DDS) patients with urogenital malformation.During analysis of WT1-associated proteins, we found that WT1 bound to Sox30, which encodes a novel transcription factor with one HMG box. Further analysis showed that WT1 bound to its HMG box. This observation prompted us to analyze interaction between WT1 and SRY, both of which are expressed in the somatic cells of early gonads. We showed the following results:i) WT1 binds to SRY in vitro and in cultured cells.ii) WT1 and SRY synergistically activate transcription from a promoter that contains SRY binding sequence and also from the SRY promoter.iii) WT1 mutants found in DDS, however, did not show this activity.iv) WT1 is recruited on a SRY-binding sequence in a SRY-dependent manner, while recruitment of DDS mutants is significantly reduced.These observations suggest that WT1 and SRY interaction plays an important role in early gonadal development and its disease. Recently we have established cell lines which express both WT1 and SRY. We are currently analyzing the expression profile of this cell line, which will reveal target genes regulated by WT1 and SRY.