Dynamic changes in mitochondrial DNA, distribution and activity within cat oocytes during folliculogenesis

Abstract

ContentsMitochondria play fundamental roles during oocyte development. The accumulation and spatial redistribution of these energy-producing organelles have been linked to the developmental competence of mammalian oocytes. Here, we assessed the copy number, distribution and activity of mitochondria within cat oocytes during folliculogenesis.In Experiment 1, oocytes were recovered from primordial (n = 152), primary (112), secondary (95), early (131), small (118), antral (86) and advanced antral (5) stages follicles, and mitochondria DNA extracted and quantified using qPCR. In Experiment 2, oocytes from pre-antral (n = 44), early antral (n = 66), small antral (n = 59), antral (n = 41) and advanced antral (n = 21) follicles were isolated and stained with CMXRos MitoTracker dye to assess mitochondrial distribution pattern and activity levels. Oocyte's mitochondria DNA (mtDNA) copy numbers gradually increased as folliculogenesis progressed, with a significant shift at the small antral stage (0.5 to <1 mm in diameter). The location of mitochondria gradually shifted from a homogeneous distribution throughout the cytoplasm in pre-antral oocytes to a pericortical concentration in the advanced antral stage. Quantification of CMXRos fluorescent intensity revealed a progressive increase in mitochondrial activity in oocytes from the pre-antral to the large antral follicles.Taken together, these findings demonstrated that cat oocytes undergo dynamic changes in mitochondrial copy number, distribution and activity during folliculogenesis. These significant modifications to this crucial cytoplasmic organelle are likely associated with the acquisition of developmental competency by cat oocytes.

Mitofusin1 in oocyte is essential for female fertility

“…Mitochondria are essential for normal cellular functions such as energy generation, calcium homeostasis, signal transduction and apoptosis [5], [6], [7]. They synthesize the vital energy currency ATP through oxidative metabolism for many processes including folliculogenesis, oocyte maturation, fertilization, and early embryonic development [8], [9]. Emerging evidence indicates that mitochondrial function is a critical determinant of oocytes developmental potential [10], [11].…”

Low Expression of Mitofusin 1 Gene Leads to Mitochondrial Dysfunction and Embryonic Genome Activation Failure in Ovine-Bovine Inter-Species Cloned Embryos

“…There is a great deal of communication between nuclear and mitochondrial genomes. Mitochondria synthesize ATP, an important energy currency, in many processes including oocyte maturation, fertilization, and early embryonic development [ 16 , 17 , 18 ]. Mitochondrial dysfunction may lead to the activation of apoptosis cascades that result in abnormal embryo development and defects [ 19 , 20 , 21 ].…”