Aberrant levels of DNA methylation and H3K9 acetylation in the testicular cells of crossbred cattle–yak showing infertility

Abstract

Although the interspecies hybridization of bovids, such as cattle–yak (Bos taurus × Bos grunniens), has heterosis benefits, the infertility of hybrid males affects the maintenance of dominant traits in subsequent generations. To achieve reproductive capacity, male germ cell development requires coordinated changes in gene expression, including DNA methylation and generalized histone modifications. Although gene expression‐related mechanisms underlying hybrid male sterility have been investigated recently, information on the cell types and stage‐specific controls remains limited. Here, we used immunohistochemistry and image analyses to evaluate the 5‐methylcytosine (5MC) and acetyl‐histone H3 Lys9 (AcK9) expression in all spermatogonia and testicular somatic cell types to determine their roles in cattle–yak spermatogenesis. Testicular tissues from yak (1–3 years old) and backcrossed hybrids (2 years old) were used. In yak, the AcK9 expression levels increased in all cell types during maturation, but the 5MC expression levels did not change until reaching 3 years when they increased in all testicular cell types, except spermatogonia. Cattle–yak hybrids showed higher 5MC expression levels and different AcK9 expression levels in all cell types compared to the same‐aged yak. These results suggested that both gene modulation by AcK9 and constant levels of DNA methylation are required for spermatogenesis during maturation in yak. Therefore, inappropriate expression levels of both AcK9 and DNA methylation might be the major factors for disruption of normal germ cell development in cattle–yak. Additionally, various modulations occurred depending on the cell type. Further experiments are needed to identify the stage‐specific gene expression modulations in each cell type in yak and cattle–yak to potentially solve the infertility issue in crossbreeding.

Disruption of cell proliferation and apoptosis balance in the testes of crossbred cattle‐yaks affects spermatogenic cell fate and sterility

“…Treatment with the histone deacetylation inhibitor trichostatin A increased AcK9 and inhibited PCNA transcription in adipose‐derived stem cells (Wang et al, 2016). Our previous study showed lower levels of AcK9 in spermatogonia and Leydig cells in hybrid cattle‐yak testes than in yaks of the same age (Phakdeedindan et al, 2021). The increased proliferation of both spermatogonia and Leydig cells in the hybrid cattle‐yak testes was thought to be one of the effects caused by lower levels of AcK9.…”

“…Furthermore, apoptosis was observed in Leydig cells in hybrid cattle-yak testes. Our previous study demonstrated that testicular cells, including spermatogonia and Leydig cells, showed higher DNA methylation in cattle-yak testes than in yaks of the same age (Phakdeedindan et al, 2021). Because DNA methylation affects genes involved in various cellular pathways, including apoptosis in cells (Gopisetty et al, 2006), different levels of apoptosis in cattleyak spermatogenic cells and Leydig cells may be induced by different levels of DNA methylation.…”

“…Treatment with the histone deacetylation inhibitor trichostatin A increased AcK9 and inhibited PCNA transcription in adipose-derived stem cells(Wang et al, 2016). Our previous study showed lower levels of AcK9 in spermatogonia and Leydig cells in hybrid cattle-yak testes than in yaks of the same age(Phakdeedindan et al, 2021). The increased proliferation of both spermatogonia and Leydig cells in the hybrid cattle-yak testes was thought to be one of the effects caused by lower levels of AcK9.The present results also showed that apoptosis increased during maturation in yaks; however, all types of somatic cells, including Sertoli cells, myoid cells and Leydig cells, showed no apoptosis at all ages, suggesting that apoptosis only occurs in spermatogenic cells during maturation in yaks with normal spermatogenesis.…”

“…To understand sterility in cattle-yak crossbreeds, we previously focused on changes in DNA methylation and histone acetylation, which can mediate the changes in gene expression of many molecules for spermatogenesis (Phakdeedindan et al, 2021). DNA methylation levels of all testicular cell types in yaks, except for spermatogonia, did not change during maturation; however, hypermethylation occurred in F2 backcross cattle-yaks, indicating that gene expression was highly suppressed (Phakdeedindan et al, 2021). In addition, acetyl-histone H3 Lys9 (AcK9) expression in spermatogonia and testicular somatic cells in F2 backcross cattle-yaks was significantly different from that in yaks of the same age (Phakdeedindan et al, 2021).…”

“…DNA methylation levels of all testicular cell types in yaks, except for spermatogonia, did not change during maturation; however, hypermethylation occurred in F2 backcross cattle‐yaks, indicating that gene expression was highly suppressed (Phakdeedindan et al, 2021). In addition, acetyl‐histone H3 Lys9 (AcK9) expression in spermatogonia and testicular somatic cells in F2 backcross cattle‐yaks was significantly different from that in yaks of the same age (Phakdeedindan et al, 2021). Therefore, we considered that inappropriate expression levels of both AcK9 and DNA methylation may be major factors in the induction of infertility in male cattle‐yaks following spermatogenesis arrest.…”