STX2 is a causative gene for nonobstructive azoospermia.

Area of Science:

• Genetics
• Reproductive Biology
• Human Molecular Genetics

Background:

• STX2 encodes a sulfoglycolipid transporter, crucial for biological processes.
• Stx2 nullizygosity in mice leads to spermatogenic failure, but human STX2 mutations remain uncharacterized.

Purpose of the Study:

• To investigate the role of STX2 mutations in human nonobstructive azoospermia.
• To identify genetic causes of male infertility in Japanese men.

Main Methods:

• STX2 mutation analysis was performed on 131 Japanese men diagnosed with nonobstructive azoospermia.
• Genetic analysis included PCR-based cDNA screening and assessment of loss-of-heterozygosity.
• Testicular histology and hormone levels were evaluated in the mutation-positive patient.

Main Results:

• A homozygous frameshift mutation (c.8_12delACCGG, p.(Asp3Alafs*8)) in STX2 was identified in one patient.
• The patient presented with azoospermia, small testes, elevated FSH, and testicular histology showing maturation arrest and multinucleated spermatocytes.
• Loss-of-heterozygosity in the STX2 region suggested potential parental consanguinity.

Conclusions:

• STX2 nullizygosity causes nonsyndromic maturation arrest with multinucleated spermatocytes in humans.
• STX2 mutations represent a rare but identifiable cause of nonobstructive azoospermia.
• This finding expands the understanding of genetic factors contributing to male infertility.