Characterization of Maternal Factor MOF/H4K16ac and the Impact of the Cryostress on Bovine Embryonic Development

Precise gene regulation is critical for mammalian embryo viability. Bovine embryos, which share high transcriptomic similarity with humans, serve as valuable models for understanding fundamental biological processes. Insights gained from studying bovine embryogenesis can transduce to broader biological research and advances facilitated reproductive technologies. Thus, investigating the molecular and cellular mechanisms in bovine embryo development, focusing on both intrinsic factors, such as maternal factors activities, and extrinsic stimuli, including assisted reproductive techniques like cryopreservation, is necessitated. The Male-on-the -First Absent (MOF) protein was identified as a critical and indispensable maternal factor activating the gene expression during embryo development in other species including Drosophila, mouse and pig. Meanwhile, the exposure of bovine blastocysts was reported to induce severe cellular activities disorders, leading to inferior quality of cryopreserved offspring. In this thesis, we present 1) the characterization of the maternal factor MOF and H4K16ac dynamics in bovine embryo development (Chapter II), and 2) the changes to the transcriptome and epigenome induced by standard and Ultra-fast cool vitrification followed by thawing in blastocysts (Chapter III). In Chapter II, we found the higher enrichment of MOF at both mRNA and protein levels during oogenesis. The abundance of MOF protein in total embryos shows a significant increase, consistent with the timing of bovine major zygotic genome activation. Moreover, we report the highest enrichment of MOF’s target, the activating histone marker H4K16ac, in the GV stage. Subsequently, H4K16ac undergoes depletion in metaphase II (MII) oocytes and de novo restoration in zygotes, suggesting the involvement of other factors in the oocyte maturation process. Our results provide insights into the maternal origin of MOF and H4K16ac and their dynamic patterns in bovine embryos, allowing continuing study of their functions during early embryogenesis. In Chapter III, we assessed the cryodamage in bovine blastocysts during the vitrification-thaw process comparing standard and Ultra-fast cooling rates, at both the transcriptome and epigenome levels. Transcriptome analysis revealed that DNA damage repair pathway genes were upregulated only in blastocysts cryopreserved with standard cooling rate, suggesting the exclusive cryodamage caused by the standard cooling protocol. Epigenetic staining results showed the elevated level of H3K9me3 in both the Standard and Ultra-fast Cool groups, elucidating the shared cryodamage induced by both vitrification methods, indicating the necessity of further improvement in cryopreservation techniques. Together, our results provide insights into the fundamental processes of embryogenesis and lead to advanced protocols for embryo cryopreservation, ultimately contributing to the knowledge of embryo development in biology.

Name thesis:degree_name

M.S., Animal Science

Level thesis:degree_level

Master of Science

Discipline thesis:degree_discipline

Animal Science

Grantor

Cornell University

Year dc:date.issued

2024

Author dc:creator

• Zhang, Jingzhi

Committee members dc:contributor.committeemember

• Cheong, Soon Hon
• Selvaraj, Vimal

• developmental biology
• embryo cryopreservation
• epigenetics modification
• ZGA

Language dc:language.iso

en

DOI

https://doi.org/10.7298/egg3-qe59

Dc Identifier Other

ProQuest Submission ID: 12236
ProQuest Publication ID: 31488608

OAI identifier oai:identifier

oai:ecommons.cornell.edu:1813/116364