Background: Human &beta-defensin 126 (12kDa) is a small cationic glycoprotein that is highly rich of cysteine. DEFB126 gene is located on the subtelomeric end of 20p1.3 in human. High expression of this protein is reported in epididymis. This polypeptide coats the plasma membrane of sperm during epididy‌mal transit. It is likely that &beta -defensin 126 might have role in unexplained male infertility since it involves in sperm maturation and capacitation. The current research designed to investigate if there is relation between &beta-defensin 126 gene mutation and unexplained male infertility.

Materials and Methods: In this case-control study we followed a two cytosine nucleotides deletion of &beta-defensin 126 gene in 35 Iranian men with unexplained infertility and 40 fertile men with normal spermogeram as control group. Standard PCR, SSCP(Single strand conformational polymorphism), and sequencing were used to detect genetic alteration of &beta-defensin 126. ELISA was performed for the assessment of the protein expression on sperm cells.

Results: Analysis of genetic data revealed 28.6% homozygote deletion in unexplained infertile men while this deletion was detected in 7.5% of controls. The deletion frequency was statistically higher in infertile patients than normal control group (p<0.05). The protein expression was less in men with del/del genotype compare to the other genotypes (p<0.005).

Conclusion: Our study shows that this common sequence variation of &beta-defensin 126 takes part in impairment of male reproductive function. Consequently, men with the del/del genotype are significantly less fertile than men who carry the wild type allele.