A conserved NR5A1-responsive enhancer regulates SRY in testis-determination.

Area of Science:

• Genetics
• Developmental Biology
• Molecular Endocrinology

Background:

• The SRY gene on the Y chromosome is essential for initiating mammalian testis development.
• The precise regulatory mechanisms controlling SRY expression remain largely unknown.
• Understanding SRY regulation is key to deciphering testis determination and related disorders.

Purpose of the Study:

• To identify and characterize regulatory elements controlling SRY gene expression in human testis determination.
• To investigate the role of the steroidogenic factor-1 (SF-1)/NR5A1 protein in SRY regulation.
• To explore the link between enhancer disruption and testis developmental abnormalities.

Main Methods:

• Comparative sequence analysis of mammalian SRY 5' regions to identify conserved motifs.
• Genomic analysis of individuals with disrupted testis determination to find mutations.
• In silico modeling and in vitro assays to assess enhancer function.
• Genome editing in a cellular model of human Sertoli cell formation.

Main Results:

• A conserved SF-1/NR5A1 binding motif was identified in an enhancer region 5 kb upstream of SRY.
• Single-base substitutions in this motif were found in individuals with disrupted testis determination.
• In vitro and genome editing experiments confirmed the enhancer's role in upregulating SRY expression.
• Disruption of this enhancer mimicked the effects of SRY coding region variants.

Conclusions:

• Human NR5A1 acts as a critical regulatory switch for testis determination by upregulating SRY expression.
• Disruption of this NR5A1 binding enhancer can cause testis dysgenesis, similar to SRY coding variants.
• Enhancer regulation plays a vital role in mammalian sex determination, with implications for understanding developmental disorders.