O-8: Some Variations of the TSSK2 Gene May be Associated with Impaired Spermatogenesis

Background: Tssk2, a member of the testis specific serine/threonine kinase (TSSK) family, is expressed predominantly in the testis and crucial for the formation and function of the sperm cells in mouse. Targeted deletion of Tssk1 and 2 in male chimeric mice caused infertility due to haploinsufficiency of the genes. Therefore it is reasonable to postulate that mutations in its human homologue TSSK2 gene may also play a role in impaired spermatogenesis in humans and our study is aimed to explore the possible association between mutations in the TSSK2 gene and idiopathic infertility in humans. Materials and Methods: A total of 494 patients with azoospermia or severe oligozoospermia and 357 fertile controls were included in our study. Mutation screening of the TSSK2 was performed by DHPLC and DNA sequencing. Genotyping was carried out by PCR restriction fragment length polymorphism. The allele and genotype frequencies of the patient and control groups were calculated by counting. The software HWE was used to evaluate the Hardy-Weinberg equilibrium of the SNPs. Differences in genotypic and allelic frequencies of the SNPs between infertile patients and controls were assessed by χ2 test using software SPSS11.0. Results: Four single nucleotide transitions were identified, including c.80 A>G (rs3747052), c.774 C>T (rs1052756)°c. 839 C>T (rs1052763)°c. 1026 G>A (rs1052773). The frequencies of minor alleles of all the 4 transitions were over 1% in both infertile patients and controls, so they were SNPs and their genotypes were in Hardy-Weinberg equilibrium. At c.80 A>G, both the frequencies of allele G (p=0.027, odds ratio (OR) =2.515, 95% confidence interval (CI) 1.077-5.868) and the genotype AG (p=0.026, OR=2.553, 95% CI 1.088- 5.993) were significantly greater in patients than those in controls. Also, the frequencies of allele T of c.774 C>T (p=0.003, OR=1.403, 95% CI 1.125-1.750) and carriers with allele T (CT+TT) (p<0.001, OR=1.571, 95% CI 1.194-2.067) were significantly higher in patients than those in controls. However, for the other two SNPs no obvious differences in either allele or genotype frequencies were found between the two groups. The allele G of c.80 A>G (rs3747052) and allele T of c.774 C>T (rs1052756) may be a genetic risk factor for the development of male infertility. Bioinformatics analysis show that the c.80A>G mutation may influence the activity of TSSK2 and the c.774C>T mutation may influence the expression of TSSK2. Conclusion: To our knowledge, present study is the first systematic mutation analysis of the TSSK2 gene in human infertility with azoospermia or severe oligozoospermia. Our findings indicate that some nucleotide variations in the TSSK2 gene may be associated with impaired spermatogenesis and male infertility