The Porcine TSPY Gene Is Tricopy but Not a Copy Number Variant

Testis-Specific Protein Y-Encoded (TSPY) Is Required for Male Early Embryo Development in Bos taurus

TSPY is a highly conserved multi-copy gene with copy number variation (CNV) among species, populations, individuals and within families. TSPY has been shown to be involved in male development and fertility. However, information on TSPY in embryonic preimplantation stages is lacking. This study aims to determine whether TSPY CNV plays a role in male early development. Using sex-sorted semen from three different bulls, male embryo groups referred to as 1Y, 2Y and 3Y, were produced by in vitro fertilization (IVF). Developmental competency was assessed by cleavage and blastocyst rates. Embryos at different developmental stages were analyzed for TSPY CN, mRNA and protein levels. Furthermore, TSPY RNA knockdown was performed and embryos were assessed as per above. Development competency was only significantly different at the blastocyst stage, with 3Y being the highest. TSPY CNV and transcripts were detected in the range of 20-75 CN for 1Y, 20-65 CN for 2Y and 20-150 CN for 3Y, with corresponding averages of 30.2 ± 2.5, 33.0 ± 2.4 and 82.3 ± 3.6 copies, respectively. TSPY transcripts exhibited an inverse logarithmic pattern, with 3Y showing significantly higher TSPY. TSPY proteins, detected only in blastocysts, were not significantly different among groups. TSPY knockdown resulted in a significant TSPY depletion (p < 0.05), with no development observed after the eight-cell stage in male embryos, suggesting that TSPY is required for male embryo development.

Copy number variation of horse Y chromosome genes in normal equine populations and in horses with abnormal sex development and subfertility: relationship of copy number variations with Y haplogroups

Structural rearrangements like copy number variations in the male-specific Y chromosome have been associated with male fertility phenotypes in human and mouse but have been sparsely studied in other mammalian species. Here, we designed digital droplet PCR assays for 7 horse male-specific Y chromosome multicopy genes and SRY and evaluated their absolute copy numbers in 209 normal male horses of 22 breeds, 73 XY horses with disorders of sex development and/or infertility, 5 Przewalski's horses and 2 kulans. This established baseline copy number for these genes in horses. The TSPY gene showed the highest copy number and was the most copy number variable between individuals and breeds. SRY was a single-copy gene in most horses but had 2-3 copies in some indigenous breeds. Since SRY is flanked by 2 copies of RBMY, their copy number variations were interrelated and may lead to SRY-negative XY disorders of sex development. The Przewalski's horse and kulan had 1 copy of SRY and RBMY. TSPY and ETSTY2 showed significant copy number variations between cryptorchid and normal males (P < 0.05). No significant copy number variations were observed in subfertile/infertile males. Notably, copy number of TSPY and ETSTY5 differed between successive male generations and between cloned horses, indicating germline and somatic mechanisms for copy number variations. We observed no correlation between male-specific Y chromosome gene copy number variations and male-specific Y chromosome haplotypes. We conclude that the ampliconic male-specific Y chromosome reference assembly has deficiencies and further studies with an improved male-specific Y chromosome assembly are needed to determine selective constraints over horse male-specific Y chromosome gene copy number and their relation to stallion reproduction and male biology.

Highly dynamic temporal changes of TSPY gene copy number in aging bulls

The Y-chromosomal TSPY gene is one of the highest copy number mammalian protein coding gene and represents a unique biological model to study various aspects of genomic copy number variations. This study investigated the age-related copy number variability of the bovine TSPY gene, a new and unstudied aspect of the biology of TSPY that has been shown to vary among cattle breeds, individual bulls and somatic tissues. The subjects of this prospective 30-month long study were 25 Holstein bulls, sampled every six months. Real-time quantitative PCR was used to determine the relative TSPY copy number (rTSPY CN) and telomere length in the DNA samples extracted from blood. Twenty bulls showed an altered rTSPY CN after 30 months, although only 9 bulls showed a significant change (4 significant increase while 5 significant decrease, P<0.01). The sequential sampling provided the flow of rTSPY CN over six observations in 30 months and wide-spread variation of rTSPY CN was detected. Although a clear trend of the direction of change was not identifiable, the highly dynamic changes of individual rTSPY CN in aging bulls were observed here for the first time. In summary we have observed a highly variable rTSPY CN in bulls over a short period of time. Our results suggest the importance of further long term studies of the dynamics of rTSPY CN variablility.

A tremendous expansion of copy number in crossbred bulls ( × )

Crossbreeding between cattle () and yak () exhibits significant hybrid advantages in milk yield and meat production. By contrast, cattle-yak F hybrid bulls are sterile. Copy number variations (CNV) of multicopy gene families in male-specific regions of the mammalian Y chromosome (MSY) affect human and animal fertility. The present study investigated CNV of (), (), (), and () in 5 yak breed bulls ( = 63), cattle-yak F ( = 22) and F ( = 2) hybrid bulls, and Chinese Yellow (CY) cattle bulls ( = 10) by quantitative real-time PCR. showed restricted amplification in yak bulls in that the average geometric mean copy number (CN) was estimated to be 4 copies. The most compelling finding is that there is a tremendous expansion of CN in F hybrids (385 copies; 95% confidence interval [CI] = 351-421) and F hybrids (356 copies) compared with the male parent breed CY cattle (142 copies; 95% CI = 95-211). Copy numbers of and were also extensively expanded on the Y chromosome in yak and CY cattle bulls. The geometric mean CN of and were estimated to be 123 (95% CI = 114-132) and 250 copies (95% CI = 233-268) in yak bulls and 71 (95% CI = 61-82) and 133 (95% CI = 107-164) copies in CY cattle, respectively. Yak and CY cattle have 2 copies of the gene on the Y chromosome. Similarly to gene, the F and F hybrid bulls have higher CN of , , and than CY cattle ( < 0.01). These results indicated that the MSY of yak and cattle-yak crossbred hybrids was fundamentally different from cattle MSY in the context of genomic organization. Based on the model of cattle-yak F and F hybrid bull sterility, the CNV of may serve as a potential risk factor for crossbred bull ( × ) infertility. To our knowledge, this is the first study to examine differences in multicopy genes in MSY between yak and cattle-yak bulls.