The Y-chromosomal and autosomal testis-determining genes

Area of Science:

• Genetics
• Developmental Biology
• Endocrinology

Background:

• XX males are individuals with 46,XX karyotype who exhibit male phenotypes.
• Testicular differentiation is primarily regulated by the testis-determining factor (TDF) on the Y chromosome.
• The genetic basis for XX maleness, particularly in cases lacking Y-DNA, requires further elucidation.

Purpose of the Study:

• To investigate the genetic mechanisms underlying XX maleness and true hermaphroditism.
• To determine the role of Y-chromosome-specific DNA (Y-DNA) and potential autosomal factors in sex determination.
• To analyze familial instances of XX testicular differentiation and inheritance patterns.

Main Methods:

• Analysis of Y-DNA sequences in XX males and XX true hermaphrodites.
• Clinical examination of individuals with ambiguous genitalia and XX karyotypes.
• Pedigree analysis of familial cases to identify inheritance patterns.

Main Results:

• A majority of XX males possess Y-DNA, implicating the TDF.
• Some XX males without detectable Y-DNA exhibit ambiguous genitalia, suggesting alternative genetic causes.
• Familial XX maleness often shows autosomal dominant inheritance, indicating the presence of an autosomal testis-determining factor (TDFA).

Conclusions:

• XX maleness can result from the presence of TDF or an autosomal dominant factor (TDFA).
• TDFA can cause variable expressivity, including true hermaphroditism and genital ambiguity in XX individuals.
• The study suggests that TDFA is responsible for XX testicular differentiation in families without detectable Y-DNA.