Human MAMLD1 Gene Variations Seem Not Sufficient to Explain a 46,XY DSD Phenotype

Area of Science:

• Genetics
• Endocrinology
• Developmental Biology

Background:

• The gene MAMLD1 is implicated in 46,XY disorders of sex development (DSD).
• However, its precise role is debated due to conflicting evidence from variant studies and knockout models.
• Some MAMLD1 variants are found in healthy individuals, and some mutations show normal function in vitro.

Purpose of the Study:

• To investigate MAMLD1 variations in 108 patients with 46,XY DSD.
• To functionally test identified MAMLD1 variants and assess their impact on sex development pathways.
• To compare Single Nucleotide Polymorphism (SNP) frequencies between patients and controls.

Main Methods:

• Screening for MAMLD1 variations in 108 46,XY DSD patients.
• Functional assays of MAMLD1 transcriptional activity on sex development-related promoters.
• Assessment of MAMLD1's effect on androgen production and protein expression via Western blots.

Main Results:

• Nine MAMLD1 mutations were identified, with seven being novel.
• Most identified MAMLD1 variants exhibited wild-type activity in functional tests.
• Only the L210X mutation demonstrated a loss of function; no significant impact on CYP17A1 activity or androgen production was observed for other variants.

Conclusions:

• MAMLD1 sequence variations alone may not be sufficient to cause the DSD phenotype in all carriers.
• MAMLD1 is expressed in adult human testes and adrenals, suggesting a potential role beyond early development.
• Further investigation is required to elucidate the complex role of MAMLD1 in sex development and adult physiology.