Expression of mitochondrial transcription factor A (TFAM) during porcine gametogenesis and preimplantation embryo development

Abstract

Mitochondrial transcription factor A (TFAM) is responsible for stability, maintenance, and transcriptional control of mitochondrial DNA (mtDNA). We have studied the expression and distribution of TFAM in the gametes and preimplantation embryos of the domestic pig (Sus scrofa). We hypothesized that TFAM is not present in the boar sperm mitochondria to reduce the possibility of paternal mtDNA propagation in the progeny. In contrast, we anticipated that Tfam gene is expressed in a developmental stage-dependent manner in porcine oocytes and embryos. The appropriate TFAM band of 25 kDa was detected by Western blotting in ejaculated boar spermatozoa, as well as in porcine oocytes and zygotes. Boar sperm extracts also displayed several bands >25 kDa suggestive of post-translational modification by ubiquitination, confirmed by affinity purification of ubiquitinated proteins. TFAM immunoreactivity was relegated to the sperm tail principal piece and sperm head in fully differentiated spermatozoa. The content of Tfam mRNA increased considerably from the germinal vesicle to blastocyst stage and also between in vitro fertilized and cultured blastocysts compared to in vivo-derived blastocysts. TFAM protein accumulated in the oocytes during maturation and was reduced by proteolysis after fertilization. This pattern was not mirrored in parthenogenetically activated oocytes and zygotes reconstructed by SCNT, suggesting deviant processing of TFAM protein and transcript after oocyte/embryo manipulation. Thus, TFAM may exert a critical role in porcine gametogenesis and preimplantation embryo development. Altogether, our data on the role of TFAM in mitochondrial function and inheritance have broad implications for cell physiology and evolutionary biology.

Posttranslational modification of mitochondrial transcription factor A in impaired mitochondria biogenesis: Implications in diabetic retinopathy and metabolic memory phenomenon

“…The presence of a high molecular weight band, instead of ~25KD band, suggests that high glucose polyubiquinated TFAM. In support others have shown tetra-ubiquitination of TFAM in sperm extracts during porcine gametogenesis (Antelman, Manandhar et al 2008). Figure 4b presents the quantification of the ubiquitinated TFAM.…”

Autophagy and ubiquitin–proteasome system contribute to sperm mitophagy after mammalian fertilization

“…S12). Mitochondrial membrane and matrix proteins such as prohibitin and TFAM, as well as those identified in the present study by copurification with the UBA domain of SQSTM1 are ubiquitinated (14,15). Thus, it is possible that the whole sperm mitochondrial sheath is recognized by the oocyte autophagy machinery as one large aggresome.…”

Regulation of mitochondrial DNA accumulation during oocyte growth and meiotic maturation in the mouse

“…Previous data that have suggested that TFAM might be a limiting factor in mtDNA replication in mammalian oocytes and embryos. In the pig, although Tfam declines during oocyte maturation (Spikings et al 2007), both TFAM (Antelman et al 2008) and mtDNA (Spikings et al 2007) accumulate during this time. Additionally, as discussed earlier, mtDNA replication resumes in embryos near the time of implantation (Piko & Taylor 1987, Ebert et al 1988, Kameyama et al 2007, May-Panloup et al 2007; in mouse and cow, this is correlated with a sharp increase in the quantity of Tfam , May-Panloup et al 2007.…”