Genetic evidence that ZFY is not the testis-determining factor

Area of Science:

• Genetics
• Developmental Biology
• Molecular Biology

Background:

• Mammalian sex determination is primarily controlled by the testis-determining gene (TDF) located on the Y chromosome.
• Previous studies localized TDF to the distal Y-specific region, near the pseudoautosomal region, through analysis of sex chromosome abnormalities.
• The ZFY gene, encoding a zinc-finger protein, was a strong candidate for TDF, but its X-linked homolog (ZFX) and autosomal homologs in marsupials raised questions.

Purpose of the Study:

• To investigate the role of the ZFY gene in male sex determination.
• To precisely map the location of the testis-determining gene (TDF) on the human Y chromosome.
• To analyze genetic exchange between sex chromosomes in individuals with atypical sex development.

Main Methods:

• Genomic analysis of XX males lacking the ZFY gene.
• Investigation of sex chromosome exchange events during male meiosis.
• Localization of Y-specific sequences relative to the pseudoautosomal boundary.

Main Results:

• XX males lacking the ZFY gene were identified and analyzed.
• These individuals exhibited male phenotypes, suggesting ZFY might not be the sole TDF.
• Crucially, genetic exchange between the X and Y chromosomes, involving Y-specific sequences near the pseudoautosomal boundary, was observed in these ZFY-negative XX males.

Conclusions:

• The findings challenge ZFY as the primary testis-determining gene.
• The observed genetic exchange redefines the critical region for TDF localization on the Y chromosome.
• TDF must lie within the newly defined region, necessitating further investigation into other candidate genes or regulatory elements.