Organizational and expressional uniqueness of a testis-specific mRNA transcript of protooncogene c-kit receptor in water buffalo Bubalus bubalis

Abstract

Protooncogene c-kit receptor is implicated with spermatogenesis, melanogenesis, and hematopoeisis, and undergoes tissue/stage specific alternate splicing. We have isolated 2973-bp full-length cDNA sequence (CDS) of this gene from testis and other tissues of water buffalo Bubalus bubalis. Upon comparison, the c-kit sequences showed tissue specific nucleotide changes resulting in novel truncated peptides. These peptides lacked intracellular and/or transmembrane domains in all the tissues except testis. Other alternately spliced tissue-specific transcripts were also detected, which are the integral parts of the open reading frame and have been reported in other mammals. Phylogenetic analysis of the sequences revealed unique tyrosine kinase domain in buffalo. Copy number calculation and expressional analysis of c-kit using real-time PCR established its single copy status and highest expression (137-177 folds) in testis compared to that (least) in liver. c-kit expression was detected in semen samples although 10 times lesser compared to that in testis. The highest expression of c-kit in testis and the presence of mRNA transcript in sperms substantiate its predominant role in spermatogenesis. This study establishes unequivocal involvement of an autosomal gene c-kit receptor in testicular function.