Abnormalities of sex differentiation

Area of Science:

• Genetics
• Endocrinology
• Developmental Biology

Background:

• Sex differentiation is a complex process involving genetic and hormonal factors.
• Key genes like DAX-1, androgen receptor, and cytochrome P450c17 play crucial roles in this cascade.
• Understanding mutations in these genes is vital for diagnosing and managing disorders of sex development.

Purpose of the Study:

• To investigate the functional roles of DAX-1, androgen receptor, and P450c17 in sex differentiation.
• To identify genetic mutations responsible for congenital adrenal hypoplasia, hypogonadotropic hypogonadism, and androgen insensitivity syndrome.
• To elucidate the structure-function relationships of the androgen receptor and the molecular basis of P450c17 deficiencies.

Main Methods:

• Analysis of DAX-1 genes in patients with congenital adrenal hypoplasia and hypogonadotropic hypogonadism using PCR and sequencing.
• Detailed analysis of 15 cases of Androgen Insensitivity Syndrome (AIS) to correlate androgen receptor gene mutations with clinical phenotypes.
• Sequencing of the CYP17 (P450c17) gene, reconstruction of mutations, and expression studies in COS1 cells to characterize enzyme activities.

Main Results:

• Identified both inherited and de novo mutations in the DAX-1 gene causing congenital adrenal hypoplasia and hypogonadotropic hypogonadism.
• Established clear structure-function relationships for the androgen receptor in 15 AIS cases.
• Characterized the kinetic properties of mutant P450c17 enzymes, revealing combined deficiencies in 17 alpha-hydroxylase and 17,20-lyase activities.

Conclusions:

• Mutations in DAX-1 are a significant cause of congenital adrenal hypoplasia and hypogonadotropic hypogonadism.
• Androgen receptor gene mutations directly correlate with the clinical spectrum of AIS.
• Deficiencies in P450c17 function underlie 17 alpha-hydroxylase deficiency, often involving combined enzymatic defects.