Aim:To identify a novel isoform of adaptin 2 beta subunit (named Ap2β-NY) and to investigate its relationship withtesticular development and spermatogenesis.Methods:Using a human testis cDNA microarray,a clone (Ap2β-NY),which was strongly expressed in adult testes but weakly expressed in embryo testes,was sequenced and analyzed.Using polymerase chain reaction (PCR),the tissue distribution and expression time pattern of Ap2β-NY were determined.Results:Ap2β-NY was identified and has been deposited in the GenBank (AY341427).The expression level ofAp2β-NY in the adult testis was about 3-fold higher than that in the embryo testis.PCR analysis using multi-tissue cDNAindicated that Ap2β-NY was highly expressed in the testis,spleen,thymus,prostate,ovary,blood leukocyte andbrain,but not in the heart,placenta,lung,liver,skeletal muscle,kidney and pancreas.In addition,Ap2β-NY wasvariably expressed in the testes of patients with spermatogenesis-disturbance and spermatogenesis-arrest but notexpressed in those of Sertoli-cell-only syndrome,which implied that,in the testis,Ap2β-NY was restrictively ex-pressed in germ cells.Conclusion:Ap2β-NY is an isoform of Ap2β and may be involved in regulating the processof spermatogenesis and testis development. Aim: To identify a novel isoform of adaptin 2 beta subunit (named Ap2β-NY) and to investigate its relationship withtesticular development and spermatogenesis. Methods: Using a human testis cDNA microarray, a clone (Ap2β-NY), which was strongly expressed in Adult testes but weakly expressed in embryo testes, was sequenced and analyzed. Using polymerase chain reaction (PCR), the tissue distribution and expression time pattern of Ap2β-NY were determined. Results: Ap2β-NY was identified and has been deposited in the GenBank (AY341427). The expression level of Ap2β-NY in the adult testis was about 3-fold higher than that in the embryo testis. PCR analysis using multi-tissue cDNAindicated that Ap2β-NY was highly expressed in the testis, spleen, thymus, prostate , ovary, blood leukocyte and brain, but not in the heart, placenta, lung, liver, skeletal muscle, kidney and pancreas.In addition, Ap2β-NY wasvariably expressed in the testes of patients with spermatogenesis-disturbance and spermatogenesis-arrest but not expressed in those of Sertoli-cell-only syndrome, which implied that, in the testis, Ap2β-NY was restrictively ex-pressed in germ cells. Conlusion: Ap2β-NY is an isoform of Ap2β and may be involved in regulating the process of spermatogenesis and testis development.