Functional study of a novel c.630delG (p.Y211Tfs*85) mutation in NR5A1 gene in a Chinese boy with 46,XY disorders of sex development

A novel MAMLD1 variant in a newborn with hypospadias and elevated 17-hydroxyprogesterone

PURPOSE

Disorders of sex development (DSD) have complex pathogenesis, and evidence suggests an association between MAMLD1 defects and DSD. MAMLD1 is expressed in gonadal tissues and affected males exhibit hypospadias, steroid hormone abnormalities, or gonadal underdevelopment. We performed genetic testing on a newborn patient with severe hypospadias and an elevation of 17-hydroxyprogesterone (17α-OH) for the diagnosis of DSD.

METHODS

Genetic testing of the proband and parents was conducted using whole-exome and Sanger sequencing. The identified variant was transfected into HEK293T cells to assess mutant protein expression using western blot (WB) and into steroidogenic NCI-H295R cells to assess MAMLD1 and CYP17A1 transcript levels using qPCR. Molecular dynamics simulations were performed to construct a structural model and analyze potential biological implications.

RESULTS

A novel heterozygous variant was identified in the proband's MAMLD1, NM_005491.5: c.1619_1637del (p.Gln540Alafs*72), inherited from the mother. In transfected cells, the wild-type and mutant proteins were 86.2 and 68.3 kDa, respectively, indicating the formation of a truncated protein. While MAMLD1 transcription was not affected, CYP17A1 transcription levels decreased with the variant compared to wild-type, suggesting an impact on the transactivation of CYP17A1. The truncated protein exhibited enhanced hydrophobicity, owing to the absence of the C-terminal structural portion, resulting in a looser protein structure.

CONCLUSION

Severe hypospadias in the proband may be attributed to a novel MAMLD1 variant, whereas the 17α-OH elevation might be related to interference with CYP17A1 transcriptional activation. This study expands the spectrum of MAMLD1 variants and underscores the critical role of genetic testing in the diagnosis of DSD.

A novel c.64G > T (p.G22C) NR5A1 variant in a Chinese adolescent with 46,XY disorders of sex development: a case report

BACKGROUND

Adolescents with 46,XY disorders of sex development (DSD) face additional medical and psychological challenges. To optimize management and minimize hazards, correct and early clinical and molecular diagnosis is necessary.

CASE PRESENTATION

We report a 13-year-old Chinese adolescent with absent Müllerian derivatives and suspected testis in the inguinal area. History, examinations, and assistant examinations were available for clinical diagnosis of 46,XY DSD. The subsequent targeting specific disease-causing genes, comprising 360 endocrine disease-causing genes, was employed for molecular diagnosis. A novel variation in nuclear receptor subfamily 5 group A member 1 (NR5A1) [c.64G > T (p.G22C)] was identified in the patient. In vitro functional analyses of the novel variant suggested no impairment to NR5A1 mRNA or protein expression relative to wild-type, and immunofluorescence confirmed similar localization of NR5A1 mutant to the cell nucleus. However, we observed decreased DNA-binding affinity by the NR5A1 variant, while dual-luciferase reporter assays showed that the mutant effectively downregulated the transactivation capacity of anti-Müllerian hormone. We described a novel NR5A1 variant and demonstrated its adverse effects on the functional integrity of the NR5A1 protein resulting in serious impairment of its modulation of gonadal development.

CONCLUSIONS

This study adds one novel NR5A1 variant to the pool of pathogenic variants and enriches the adolescents of information available about the mutation spectrum of this gene in Chinese population.

Diverse Regulation but Conserved Function: SOX9 in Vertebrate Sex Determination

Sex determination occurs early during embryogenesis among vertebrates. It involves the differentiation of the bipotential gonad to ovaries or testes by a fascinating diversity of molecular switches. In most mammals, the switch is SRY (sex determining region Y); in other vertebrates it could be one of a variety of genes including Dmrt1 or dmy. Downstream of the switch gene, SOX9 upregulation is a central event in testes development, controlled by gonad-specific enhancers across the 2 Mb SOX9 locus. SOX9 is a ‘hub’ gene of gonadal development, regulated positively in males and negatively in females. Despite this diversity, SOX9 protein sequence and function among vertebrates remains highly conserved. This article explores the cellular, morphological, and genetic mechanisms initiated by SOX9 for male gonad differentiation.

Disorders of Sex Development: Classification, Review, and Impact on Fertility

In this review, the elements included in both sex determination and sex differentiation are briefly analyzed, exposing the pathophysiological and clinical classification of disorders or anomalies of sex development. Anomalies in sex determination without sex ambiguity include gonadal dysgenesis, polysomies, male XX, and Klinefelter syndrome (dysgenesis and polysomies with a female phenotype; and sex reversal and Klinefelter with a male phenotype). Other infertility situations could also be included here as minor degrees of dysgenesis. Anomalies in sex determination with sex ambiguity should (usually) include testicular dysgenesis and ovotesticular disorders. Among the anomalies in sex differentiation, we include: (1) males with androgen deficiency (MAD) that correspond to those individuals whose karyotype and gonads are male (XY and testes), but the phenotype can be female due to different hormonal abnormalities. (2) females with androgen excess (FAE); these patients have ovaries and a 46,XX karyotype, but present varying degrees of external genital virilization as a result of an enzyme abnormality that affects adrenal steroid biosynthesis and leads to congenital adrenal hyperplasia; less frequently, this can be caused by iatrogenia or tumors. (3) Kallman syndrome. All of these anomalies are reviewed and analyzed herein, as well as related fertility problems.