The 23rd International Symposium on Developmental Biotechnology[Geun-Hwi Jo] > 학회발표

Role of ATF5 in Maintaining Mitochondrial Proteostasis and Embryo Quality under Heat Stress in Bovine Oocytes During In vitro culture

Geun-Hwi Jo^1,2*, Hyo-Jin Park^1,2, Jin-Hyuk Yoo^1,2and Deog-Bon Koo^1,2,3

¹Department of Biotechnology, College of Engineering, ²Center for Infertility, ³Department of Companion Animal Industry, College of Natural and Life Sciences, Daegu University, 201 Daegudae-ro Jillyang, Gyeongsan, Gyeongbuk 38453, Republic of Korea

Heat stress (HS) impairs the reproductive performance of livestock animals by disrupting oocyte development, embryonic progression, and conception rates. Elevated temperatures during in vitro culture induce oxidative stress and mitochondrial dysfunction in early embryos, resulting in reduced blastocyst formation. However, the link between mitochondrial unfolded protein response (UPR^mt) signaling, particularly activating transcription factor 5 (ATF5), and mitochondrial function in bovine oocytes under HS remains unclear.

In current study, cumulus–oocyte complexes (COCs) were matured for 22 h at either 38.5 °C (control, Con) or 41.5 °C (HS), followed by in vitro fertilization (IVF) and 7 days of embryo culture. Cleavage and blastocyst formation rates, mitochondrial membrane potential (ΔΨm), reactive oxygen species (ROS), and calcium (Ca²⁺) levels were assessed using JC-1, MitoSOX, and Rhod-2 staining. Blastocyst formation was significantly lower in the HS group (p < 0.01), accompanied by decreased ΔΨm and increased ROS and mitochondrial Ca²⁺ accumulation. Immunofluorescence showed enhanced nuclear localization of ATF5 in HS blastocysts, and qPCR revealed elevated expression of UPR^mt-related genes (Lonp1, HSPD1, HSPA9 as ATF5 downstream factors). Furthermore, RNA-seq analysis of HS-treated oocytes showed distinct gene expression changes across categories, with upregulation of mitochondrial stress-response genes and downregulation of energy metabolism-related genes (e.g., [00]↑, [00]↓), indicating disrupted mitochondrial homeostasis.

These results demonstrate that HS during oocyte maturation induces ATF5-mediated mitochondrial dysfunction in bovine embryos during IVC process, suggesting a critical role for ATF5 in preserving oocyte viability and developmental competence under thermal stress.

Keywords) Heat stress (HS), Mitochondrial Unfolded Protein Response (UPR^mt), Bovine embryos, ATF5, In vitro culture(IVC) 

E-mail : rmsgnl159@naver.com (Geun-Hi Jo)

Funding

This work was supported by the National Research Foundation of Korea (NRF) funded by the government (MSIT) of the Republic of Korea (RS-2021-NR061941 and RS-2022-NR069006). This study was supported by the Gyeongsangbuk-do Regional Innovation System and Education (RISE) Project.