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.