Molecular mechanism of sex determination and its disease

在人类中，与其他哺乳动物一样，性别决定是由一个显性开关控制的，该开关被称为睾丸决定因子（Testis Determining Factor）。SRY基因被认为是TDF，其编码具有一个HMG盒作为DNA结合结构域的转录因子。在人类15%的XY性反转病例中，已经确定了SRY HMG盒中的突变。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，人们对SRY的转录调节机制知之甚少。另一种转录因子WT 1在伴有泌尿生殖畸形的Denys-Drash综合征（DDS）患者中也经常发生突变，在分析WT 1相关蛋白的过程中，我们发现WT 1与Sox 30结合，后者编码一种新的具有一个HMG盒的转录因子。进一步分析表明WT 1与其HMG盒结合。这一观察结果促使我们分析WT 1和SRY之间的相互作用，这两者都在早期性腺的体细胞中表达。我们在Oncogene上发表了一篇论文，描述了以下结果。i）WT 1在体外和培养的细胞中与SRY结合，并且这种相互作用由WT 1的锌指结构域和SRY的HMG盒介导。ii）WT 1和SRY协同激活从含有SRY结合序列的启动子以及从SRY启动子的转录。然而，DDS中发现的WT 1突变体没有显示出这种活性。（3）WT 1以SRY依赖的方式被募集到SRY结合序列上，而DDS突变体的募集则被显著抑制，这表明WT 1和SRY的相互作用在性腺发育早期及其疾病中起着重要作用。

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. Mutations of another transcription factor, WT1, are frequently 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 published a paper describing the following results in Oncogene. i) WT1 binds to SRY in vitro and in cultured cells and this interaction is mediated by the zinc finger domain of WT1 and the HMG box of SRY. ii) WT1 and SRY synergistically activate transcription from a promoter that contains SRY binding sequence and also from the SRY promoter. WT1 mutants found in DDS, however, did not show this activity. iii) WT1 is recruited on a SRY-binding sequence in a SRY dependent manner, while recruitment of DDS mutants is significantly inhibited.These observations suggest that WT1 and SRY interaction plays an important role in early gonadal development and its disease.