The spermatogenesis and oogenesis-specific helix-loop-helix transcription factor 2 (Sohlh2) is exclusively expressed in germ cells of male and female gonad. Sohlh2 acts as a transcriptional factor via its specific DNA binding site, E-box to regulate target genes such as Lhx8, Zp genes, Ngn3. Sohlh2 localize in the female oocyte and in the male spermatogonia. However, the regulatory mechanism of Sohlh2 was poorly understood. In this study, we examine the patterns interacting with Sohlh2. First, we performed immunoprecipitation with the antibody against Sohlh2 protein extracts from the testis. Two-dimensional SDS-gel showed sexual distinguishable protein including Fkbp12, 13, 3, 59. Among them, Fkbp3 is a member of the immunophilin protein family, which play a role in immunoregulation and basic cellular processes involving protein folding and trafficking. Protein is a cis-trans prolyl isomerase that binds the immunosuppressants FK506 and rapamycin. It has a higher affinity for rapamycin than for FK506 and thus may be an important target molecule for immunosuppression by rapamycin. In the expression analysis of Fkbp3 is detected in the multiple tissues; intestine, stomach, kidney, spleen, liver, heart, brain, lung, uterus, ovary, testis. Here, we identified that Fkbp3 mRNA is detected in the ovary and testis, kidney, liver, heart, brain, lung. Immunostaning assay shows that Fkbp3 is localized at the spermatogonia in testis. In further studies, in order to confirm the interaction between Fkbp3 and Sohlh2, we will perform immunoprecipitation.

The spermatogenesis and oogenesis-specific helix-loop-helix transcription factor 2 (Sohlh2) is exclusively expressed in germ cells of male and female gonad. Sohlh2 acts as a transcriptional factor via its specific DNA binding site, E-box to regulate target genes such as Lhx8, Zp genes, Ngn3. Sohlh2 localize in the female oocyte and in the male spermatogonia. In recent studies, Sohlh2 knockout (KO) mice occurs abnormal spermagoenesis resulting in sperm defect. Sohlh2 KO male mice were infertility due to disruption of numerous gene expression. However, the gene profiles of Sohlh2 KO testes were not characterized and the regulatory mechanism of Sohlh2 was poorly understood. In this study, we analyzed the gene profiles and examined the possible mechanism of Sohlh2 in the spermatogenesis. First, we performed histological analysis such as Hematoxylin and eosin stain, Tunel assay, and Immunohistochemistry to show the onset of disruption of Sohlh2 KO testes. These results showed that Sohlh2 KO testes have atrophic seminiferous tubule due to increased apoptosis at 2 weeks old. And then we analyzed the whole gene profiles in the Sohlh2 KO testes at 2 weeks old. We found that 91 genes were regulated at least 5-fold in knockout testes. Among these, several genes are involved in meiotic process. Quantitative-PCR results are shown that several meiotic factors are significantly down-regulated in 2-weeks-old Sohlh2 KO testes compared with that of wild type mice. Through chromosome spreading assay, we observed that the formation of synaptonemal complex of homologous chromosome during the meiosis in Sohlh2 KO testes was not completed. These suggest that Sohlh2 is critical for regulation of numerous factors including meiotic factors either directly or indirectly. Therefore, mis-regulation of meiotic factors at prophase I of meiosis during spermatogenesis leads to disruption of spermatogenesis in Sohlh2 KO testes. Further studies are needed to look at the mechanism of Sohlh2 for regulation of target genes in detail.

SOHLH2 is a novel germ cell-specific transcription factor that is crucial for folliculogenesis in the ovary and spermatogenesis in the testis. SOHLH2 represents a candidate gene for infertility with premature ovarian failure. We analyzed whether mutations in the SOHLH2 gene in 98 Korean women with premature ovarian failure. The sequence analysis identified six novel SNPs (c.431-41G>C, c.656A>T, c.1000+27C>T, c.1000+33G>T, c1258-106G>A, and c.2094+ 11T>C) from Korean patients with premature ovarian failure. The c.656A>T found in exon 7 results in change of an amino acid, tyrosine to phenylalanine. Functional mutations in SOHLH2 gene are rare in Korean women with premature ovarian failure.