Abstract
BackgroundThe Y chromosome in mammal is paternally inherited and harbors genes related to male fertility and spermatogenesis. The unique intra-chromosomal recombination pattern of Y chromosome and morphological difference of this chromosome between Bos taurus and Bos indicus make it an ideal model for studying structural variation, especially in crossbred (Bos taurus × Bos indicus) bulls. Copy Number Variation (CNV) is a type of genomic structural variation that gives information complementary to SNP data. The purpose of this study was to find out copy number differences of four Y chromosomal spermatogenesis-related candidate genes in genomic DNA of crossbred and purebred Indicine bulls.ResultFour Y chromosomal candidate genes of spermatogenesis namely, sex determining gene on Y chromosome (SRY), DEAD box polypeptide 3-Y chromosome (DDX3Y), Ubiquitin specific peptidase 9, Y-linked (USP9Y), testis-specific protein on Y chromosome (TSPY) were evaluated. Absolute copy numbers of Y chromosomal genes were determined by standard curve-based quantitative real time PCR. Copy numbers of SRY and TSPY genes per unit amount of genomic DNA are higher in crossbred than Indicine bulls. However, no difference was observed in DDX3Y and USP9Y gene copy numbers between two groups.ConclusionThe present study demonstrates that the structural organization of Y chromosomes differs between crossbred and Indicine bulls which are reproductively healthy as observed from analysis of semen attributes. The absolute copy numbers of SRY and TSPY genes in unit mass of genomic DNA of crossbred bulls are significantly higher than Indicine bulls. No alteration in absolute copies of DDX3Y and USP9Y gene was found between the genome of crossbred and Indicine bulls. This study suggests that the DDX3Y and USP9Y are likely to be single copy genes in the genome of crossbred and Indicine bulls and variation in Y chromosome length between crossbred and Indicine bulls may be due to the copy number variation of SRY gene and TSPY array.
Highlights
The Y chromosome in mammal is paternally inherited and harbors genes related to male fertility and spermatogenesis
The absolute copy numbers of sex determining gene on Y chromosome (SRY) and testis-specific protein on Y chromosome (TSPY) genes in unit mass of genomic DNA of crossbred bulls are significantly higher than Indicine bulls
No alteration in absolute copies of DEAD box polypeptide 3-Y chromosome (DDX3Y) and USP9Y gene was found between the genome of crossbred and Indicine bulls
Summary
The Y chromosome in mammal is paternally inherited and harbors genes related to male fertility and spermatogenesis. The unique intra-chromosomal recombination pattern of Y chromosome and morphological difference of this chromosome between Bos taurus and Bos indicus make it an ideal model for studying structural variation, especially in crossbred (Bos taurus × Bos indicus) bulls. The purpose of this study was to find out copy number differences of four Y chromosomal spermatogenesis-related candidate genes in genomic DNA of crossbred and purebred Indicine bulls. In absence of inter-chromosomal recombination the repeated gene sequences within a chromatid or between sister chromatids act as substrates for recombination. The protein product of the TSPY gene probably interacts with type B cyclins and activates cyclin B-CDK complexes. The activated complex, in turn, impacts on biological machineries in spermatogonial cell renewal and in prophase I spermatocyte differentiation [13]
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