Sperm-borne small RNAs regulate α-tubulin acetylation and epigenetic modification of early bovine somatic cell nuclear transfer embryos

Abstract

Accumulated evidence indicates that sperm-borne small RNA plays a crucial role in embryonic development, especially the absence of the sperm-borne small RNA might be a major cause of the abnormal development of cloned embryos. In this study, we found that sperm-borne small RNA can affect abnormal pronuclear-like structures, postpone the timing of first embryo cleavage and enhance developmental competence of bovine somatic cell nuclear transfer (SCNT) embryos. In addition, the supplementation of sperm-borne small RNA can significantly increase live birth rates and decrease the birth weights of cloned offspring. To investigate the underlying mechanisms, the levels of α-tubulin K40 acetylation (Ac α-tubulin K40) and histone H3 lysine 9 trimethylation (H3K9me3) during early embryo development were investigated in SCNT embryos with sperm-borne small RNA supplementation (termed as T-NT), compared to those normal SCNT embryos and embryos obtained from standard IVF. The results showed that sperm-borne small RNA can significantly decrease the H3K9me3 levels at the pronuclear and two-cell stages, while significantly increase Ac α-tubulin K40 levels at anaphase and telophase of bovine SCNT embryos during the first cleavage. Collectively, our study for the first time demonstrates that sperm-borne small RNA plays a crucial role in the developmental competence of SCNT embryos by regulating H3K9me3 and Ac α-tubulin K40. Further studies will be required to determine how sperm small RNA regulate the H3K9me3 and Acα-tubulin K40. Our study suggests that the supplementation of sperm-borne small RNA is a potential application to improve the cloning efficiency.

Insights into the roles of sperm in animal cloning

“…The drastic PTM-mediated cytoskeletal remodeling undoubtedly plays an important role during embryo development. A recent study found a different α-tubulin acetylation pattern between SCNT and fertilized embryos [39].…”

“…Significant differences in cytoskeletal organization and post-transcriptional modification of cytoskeleton were observed in SCNT and IVF embryos. The abnormal cytoskeleton remodeling was considered to be responsible for the abnormal development of SCNT embryos, in particular abnormal pronuclear structures, faster development kinetics, and higher ratio of blastomere fragments [39].…”

“…Abnormal centrosomes and failed "pronuclear" migration are related to errors in spindle morphology, chromosome alignment, and cytokinesis in SCNT embryos, which can lead to chromosome instability, disorder of transcriptional regulation and DNA replication, and DNA damage [44]. The complete deletion of sperm regulators in SCNT embryos may be an important reason for the abnormal PCC and pronucleus formation [39].…”

“…Sperm small RNA could regulate the epigenetic state and cytoskeleton remodeling in SCNT embryos (Fig. 2), [39]. Many studies have been performed on individual sample types, such as oocytes, sperm, or donor cells.…”

“…piRNA is also involved in maternal mRNA degradation and plays an important role in regulating protein translation, mediating ubiquitination degradation, germ cell development, sex determination, and embryonic development. The latest study found that H3K9me3 in SCNT embryos significantly reduced, and injecting small RNA into SCNT embryos could significantly enhance cloning efficiency [39]. The molecular mechanism of action of sperm small RNA in regulating SCNT embryo reprogramming is still not clear and needs to be explored in subsequent studies.…”