Genetic Polymorphisms within The Intronless ACTL7A and ACTL7B Genes Encoding Spermatogenesis-Specific Actin-Like Proteins in Japanese Males

Actins play essential roles in cellular morphogenesis. In mice, the t-actin 1 and 2 genes, which encode actin-like proteins, are specifically expressed in haploid germ cells. Both T-ACTIN 1/ACTLB and T-ACTIN 2/ACTL7A have also been cloned as orthologous genes in humans; they are present on chromosome 9q31.3 as intronless genes. Defects of germ cell-specific genes can introduce infertility without somatic function impairment. We defined T-ACTIN 1 and T-ACTIN 2, which are also specifically expressed in the testis by reverse-transcription polymerase chain reaction (RT-PCR). To examine whether genetic polymorphisms of the T-ACTIN 1 and 2 genes are associated with male infertility, we screened for T-ACTIN 1 and 2 polymorphisms by direct the sequencing of DNA from 282 sterile and 89 fertile Japanese men. We identified five and six single nucleotide polymorphisms (SNPs) in the T-ACTIN 1 and 2 regions, respectively, in 371 subjects. Among these genetic polymorphisms was a novel SNP that was not in the National Center for Biotechnology Information SNP database. Although we could not determine whether these SNPs cause infertility, the prevalence of these genetic polymorphisms may be useful for analyzing polymorphisms in future large-scale genetic analyses.