Alternative splicing, chromosome assignment and subcellular localization of the testicular haploid expressed gene (THEG).

We have previously isolated and characterized the mouse Testicular Haploid Expressed Gene (Theg) that is specifically expressed in haploid germ cells. We now describe the molecular cloning and characterization of the human homologue (THEG) of mouse Theg. Expression studies by using both dot blot and Northern blot techniques revealed that human THEG is expressed specifically in the testis. Additionally, we found two alternatively spliced transcripts (THEG major and THEG minor) for THEG by using reverse transcription-polymerase chain reaction on human testicular RNA. Sequence analysis of these PCR products demonstrated that the smaller transcript (THEG minor) lacks 72 bp which was also observed for the mouse Theg. We have isolated the cDNAs of human THEG major and THEG minor, containing the complete open reading frames, which encode putative nuclear proteins of 379 amino acids and 355 amino acids, respectively. Database searches identified two genomic clones on chromosome 19 harboring the human THEG gene, which is approximately 14 kb pairs in size, contains eight exons, and comparison of the two cDNA sequences with the genomic sequence indicated that the smaller transcript lacks exon 3. Furthermore, we assigned the human THEG gene (THEG) to human chromosome 19ptel--> p13 by fluorescence in situ hybridization. Moreover, we detected mouse THEG protein prominently in the nucleus of round spermatids by using an antibody against THEG on both testicular sections and cellular suspensions. Additionally, the subcellular localization of mouse THEG was confirmed by a green fluorescent protein (GFP) fusion protein of mouse THEG which was found mainly in the nucleus of transfected NIH3T3 cells. These data suggest that both human and mouse THEG are specifically expressed in the nucleus of haploid male germ cells and are involved in the regulation of nuclear functions.