title: Inherited human sex reversal due to impaired nucleocytoplasmic trafficking of SRY defines a male transcriptional threshold.
abstract: 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.
authors.affiliation: Departments of Biochemistry, Biomedical Engineering, and Medicine, Case Western Reserve University, Cleveland, OH 44106.
authors.forename: Yen-Shan
authors.initials: YS
authors.lastname: Chen
authors.forename: Joseph D
authors.initials: JD
authors.lastname: Racca
authors.forename: Nelson B
authors.initials: NB
authors.lastname: Phillips
authors.forename: Michael A
authors.initials: MA
authors.lastname: Weiss
mesh_terms: D021581:Active Transport, Cell Nucleus / Q000502:physiology; D015153:Blotting, Western; D002454:Cell Differentiation / Q000502:physiology; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism*; D047369:Chromatin Immunoprecipitation; D005260:Female; D018507:Gene Expression Regulation, Developmental / Q000235:genetics*; D006061:Gonadal Dysgenesis, 46,XY / Q000235:genetics*; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D008958:Models, Molecular; D011487:Protein Conformation; D055758:SOX9 Transcription Factor / Q000235:genetics / Q000378:metabolism*; D012708:Sertoli Cells / Q000166:cytology; D051876:Sex-Determining Region Y Protein / Q000235:genetics* / Q000378:metabolism*; D013737:Testis / Q000254:growth & development*
chemical_list: D055758:SOX9 Transcription Factor; C527932:SOX9 protein, human; C497745:SRY protein, human; D051876:Sex-Determining Region Y Protein
keywords: gene-regulatory network; gonadogenesis; organogenesis; protein-DNA interaction; sex determination