Inherited human sex reversal due to impaired nucleocytoplasmic trafficking of SRY defines a male transcriptional threshold
Inherited human sex reversal due to impaired nucleocytoplasmic trafficking of SRY defines a male transcriptional threshold
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DOI：
10.1073/pnas.1300828110
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发表时间：
2013-09-17
影响因子：
11.1
通讯作者：
Weiss, Michael A.
中科院分区：
文献类型：
--
作者：
Chen, Yen-Shan;Racca, Joseph D.;Weiss, Michael A.
人类的睾丸决定是由Y染色体上的性别决定区（SRY）启动的。SRY基因突变导致性腺发育不全，表现为女性体细胞表型。两个微妙的变体（V60 L和I90 M在高迁移率族盒）定义了遗传等位基因共享的XY不育女儿和可育父亲。而特定的DNA结合和弯曲在大鼠胚胎前支持细胞系中不受影响，由于受损的核输入（V60 L;由Exportin-4介导）或输出（I90 M;由染色体区域维持1介导），变体在核质穿梭中表现出选择性缺陷。穿梭减少限制了磷酸化（活化）SRY的核积累，从而减少了调节支持细胞分化的DNA位点[睾丸特异性SRY盒9（Sox 9）增强子]的占用。尽管生物化学和细胞生物学扰动的不同模式，V60 L和I90 M各自在瞬时转染测定中将Sox 9表达减弱两倍。在V60 A的研究中也观察到这种衰减，V60 A是一种与卵睾丸相关的临床变体，因此不同细胞命运之间存在不确定性。这个共有的双重阈值让人想起转录因子单倍不足的常染色体综合征，包括与SOX 9突变相关的XY性逆转。我们的研究结果表明，SRY的核质穿梭是必要的睾丸发育的强大启动。虽然也有特征的有蹄类动物的直系同源物，这种穿梭是不保守的啮齿类动物，其中受损的核出口的高迁移率族盒和进口依赖性磷酸化的补偿微卫星相关的转录激活结构域。由于SRY核质穿梭的细微缺陷导致的人类性别逆转表明其转录活性处于发育模糊的边缘。
Human testis determination is initiated by SRY (sex determining region on Y chromosome). Mutations in SRY cause gonadal dysgenesis with female somatic phenotype. Two subtle variants (V60L and I90M in the high-mobility group box) define inherited alleles shared by an XY sterile daughter and fertile father. Whereas specific DNA binding and bending are unaffected in a rat embryonic pre-Sertoli cell line, the variants exhibited selective defects in nucleocytoplasmic shuttling due to impaired nuclear import (V60L; mediated by Exportin-4) or export (I90M; mediated by chromosome region maintenance 1). Decreased shuttling limits nuclear accumulation of phosphorylated (activated) SRY, in turn reducing occupancy of DNA sites regulating Sertoli-cell differentiation [the testis-specific SRY-box 9 (Sox9) enhancer]. Despite distinct patterns of biochemical and cell-biological perturbations, V60L and I90M each attenuated Sox9 expression in transient transfection assays by twofold. Such attenuation was also observed in studies of V60A, a clinical variant associated with ovotestes and hence ambiguity between divergent cell fates. This shared twofold threshold is reminiscent of autosomal syndromes of transcription-factor haploinsufficiency, including XY sex reversal associated with mutations in SOX9. Our results demonstrate that nucleocytoplasmic shuttling of SRY is necessary for robust initiation of testicular development. Although also characteristic of ungulate orthologs, such shuttling is not conserved among rodents wherein impaired nuclear export of the high-mobility group box and import-dependent phosphorylation are compensated by a microsatellite-associated transcriptional activation domain. Human sex reversal due to subtle defects in the nucleocytoplasmic shuttling of SRY suggests that its transcriptional activity lies near the edge of developmental ambiguity.