The relationship between transcript expression levels of nuclear encoded (TFAM, NRF1) and mitochondrial encoded (MT-CO1) genes in single human oocytes during oocyte maturation

Abstract

In some cases of infertility in women, human oocytes fail to mature when they reach the metaphase II (MII) stage. Mitochondria plays an important role in oocyte maturation. A large number of mitochondrial DNA (mtDNA), copied in oocytes, is essential for providing adenosine triphosphate (ATP) during oocyte maturation. The purpose of this study was to identify the relationship between transcript expression levels of the mitochondrial encoded gene (MT-CO1) and two nuclear encoded genes, nuclear respiratory factor 1 (NRF1) and mitochondrial transcription factor A (TFAM) in various stages of human oocyte maturation. Nine consenting patients, age 21-35 years old, with male factors were selected for ovarian stimulation and intracytoplasmic sperm injection (ICSI) procedures. mRNA levels of mitochondrial-related genes were performed by singlecell TaqMan® quantitative real-time polymerase chain reaction (qRT-PCR). There was no significant relationship between the relative expression levels in germinal vesicle (GV) stage oocytes (p = 0.62). On the contrary, a significant relationship was seen between the relative expression levels of TFAM and NRF1 and the MT-CO1 genes at the stages of metaphase I (MI) and MII (p = 0.03 and p = 0.002). A relationship exists between the transcript expression levels of TFAM and NRF1, and MT-CO1 genes in various stages of human oocyte maturation.

Keywords: Mitochondria; Oocyte maturation; Quantitative real-time polymerase chain reaction (qRT-PCR); single-cell.

Figure 1

Relationship between mitochondrial related mRNA expression levels of TFAM, NRF1 and MTCO1 genes at GV, MI, MII stages of human oocyte maturation (A, B, C, respectively). A: p = 0.62; B: p = 0.03; C: p = 0.002. Superscript asterisk (*) shows statically significant differences (<0.05). Data are presented as means ± standard deviation (SD).

Figure 2

Relationship between the mean relative expression levels of nuclear encoded (TFAM, NRF1) and the mitochondrial encoded (MT-CO1) genes at various stages of the human oocyte maturation. GV: p = 0.58; MI: p = 0.23; MII: p = 0.012. Superscript asterisk (*) shows statically significant differences (<0.05). Data are presented as means ± standard deviation (SD).