Expression of a novel bHLH-Zip gene in human testis

Aim: To identify specifically expressed genes in the adult and fetal testes. Methods: A human testis cDNA microarray was established. Then the mRNA of adult and fetal testis was purified and probes were prepared by a reverse transcription reaction with the testis mRNA as template. The microarray was hybridized with probes of adult and fetal testes. The nucleic sequences of differentially expressed genes were determined and homologies were searched in the databases of the GenBank. Results: When hybridized with adult or fetal testis probes, the positive clones were 96.8 % and 95.4 %, respectively. Among these genes, one was a new testis-specific gene, which was named TSPI. TSPI was highly expressed in human adult testis. The cDNA of TSPI was 1,484 bp in length. The cDNA sequence of this clone was deposited in the Genbank (AF333098). TSPI was also determined as Interim Gen Symbol (Unigene, No. Hs.98266). Protein analysis showed that TSPI contained two functional domains: an N-terminal basic helix-loop-helix (bHLH) and a C-terminal leucine zipper (Zip). Homologous analysis showed that the 430 amino acid sequences deduced from the 1,293 bp open reading frame (ORF) had a homology with the human gene FLJ2509 (AK098575). TSPI had also a sequence homology with Spz I protein of mouse. Expression profiles showed that TSPI was specifically and strongly expressed in the testis. Conclusion: TSP1 is a gene highly expressed in adult testis. It may play an important role in spermatogenesis in the humans.