The Infertility of Repeat-Breeder Cows During Summer Is Associated with Decreased Mitochondrial DNA and Increased Expression of Mitochondrial and Apoptotic Genes in Oocytes

Author(s)

Ferreira, Roberta Machado ; Chiaratti, Marcos Roberto ; Macabelli, Carolina Habermann ; Rodrigues, Carlos Alberto ; Ferraz, Marcio Leao ; Watanabe, Yeda Fumie ; Smith, Lawrence Charles ; Meirelles, Flavio Vieira ; Baruselli, Pietro Sampaio

• Document type: Journal article
• Source: BIOLOGY OF REPRODUCTION; v. 94, n. 3 MAR 1 2016.
• Web of Science Citations: 17

Abstract

Oocyte quality is known to be a major cause of infertility in repeat-breeder (RB) and heat-stressed dairy cows. However, the mechanisms by which RB oocytes become less capable of supporting embryo development remain largely unknown. Thus, the aim of this study was to investigate whether the decreased oocyte competence of RB cows (RBs) during summer is associated with an altered gene expression profile and a decrease in mitochondrial DNA (mtDNA) copy number. Therefore, oocytes collected from heifers, non-RBs in peak lactation (PLs), and RBs were used to evaluate mtDNA amounts as well as the expression levels of genes associated with the mitochondria (MT-CO1, NRF1, POLG, POLG2, PPARGC1A, and TFAM), apoptosis (BAX, BCL2, and ITM2B), and oocyte maturation (BMP15, FGF8, FGF10, FGF16, FGF17, and GDF9). The oocytes retrieved from RBs during winter contained over eight times more mtDNA than those retrieved from RBs during summer. They also contained significantly less mtDNA than oocytes retrieved from heifers and PLs during summer. Moreover, the expression of mitochondria-(NRF1, POLG, POLG2, PPARGC1A, and TFAM) and apoptosis-related (BAX and ITM2B) genes, as well as of GDF9, in RB oocytes collected during summer was significantly greater than that in oocytes collected from heifers and PLs during the same season. In oocytes from heifers and PLs, the expression levels of these genes were lower in those collected during summer compared with winter, but this difference was not observed in oocytes collected from RBs. Altogether, these data provide evidence of altered gene expression and reduced mtDNA copy number in the oocytes collected from RBs during summer. This indicates a loss of fertility in RBs during summer, which might be caused by a possible mitochondrial dysfunction associated with a greater chance of oocytes to undergo apoptosis. (AU)

• FAPESP's process: 09/00938-3 - Effect of season on oocyte quality and in vitro embryo production in Holstein cows (Bos taurus) of different categories
• Grantee: Pietro Sampaio Baruselli
• Support Opportunities: Regular Research Grants
• FAPESP's process: 10/13384-3 - Effect of introducing embryonic or somatic mitochondria on development and on mitochondrial inheritance in cattle
• Grantee: Flávio Vieira Meirelles
• Support Opportunities: Regular Research Grants
• FAPESP's process: 11/14207-0 - Effect of season on oocyte quality of buffaloes (Bubalus bubalis): analysis of gene expression and mitochondrial DNA copy number
• Grantee: Carolina Habermann Macabelli
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• FAPESP's process: 10/09561-7 - Effect of introducing a large amount of embryonic or somatic mitochondria on development and on mitochondrial inheritance in bovines
• Grantee: Marcos Roberto Chiaratti
• Support Opportunities: Scholarships in Brazil - Post-Doctoral
• FAPESP's process: 12/07510-1 - Molecular evaluation of oocyte maturation and use of cytoplasmic transfer to increse oocyte competence of repeat breeder dairy cows
• Grantee: Roberta Machado Ferreira Saran
• Support Opportunities: Scholarships in Brazil - Post-Doctoral