Expression of a novel dipeptidyl peptidase 8 (DPP8) transcript variant, DPP8-v3, in human testis

Aim: To investigate the role of a novel dipeptidyl peptidase 8 transcript variant (DPP8-v3) gene in testis development and/or spermatogenesis. Methods: A human testis cDNA microarray was hybridized with mRNA of human adult and fetal testes. Differentially expressed clones were sequenced and characterized and their expression was analyzed by real-time reverse transcription polymerase chain reaction (RT-PCR) and Southern-blot analysis. Results: A new transcript variant of the human dipeptidyl peptidase (DPP8), exhibiting a 5-fold higher expression level in human adult than that in fetal testes, was cloned and was named DPP8 variant 3 (DPP8-v3). The full-length sequence of DPP8-v3 was 3,030 bp, encoding a protein of 898 amino acids. Conclusion: DPP8-v3 is a novel human DPP8 transcript variant highly expressed in the adult testis. Similar to DPPIV, DPP8-v3 may play a key role in the immunoregulation of testes and accordingly may influence spermatogenesis and male fertility.