Conclusions
These data provide new insight into the protective role that MCU-dependent mitochondrial Ca2+ signalling plays in meiotic progress, in addition to demonstrating a new mechanism of mitochondrial energy regulation by AMPK signalling that influences meiotic maturation.
Methods
We demonstrated that cell cycle-dependent mitochondrial Ca2+ connects energy sensing to mitochondrial activity in meiosis progression within mouse oocytes. Further, we established a model in mouse oocytes using siRNA knockdowns that target mitochondrial calcium uniporters (MCUs) in order to inhibit mitochondrial Ca2+ concentrations.
Results
Decreased numbers of oocytes successfully progressed to the germinal vesicle stage and extruded the first polar body during in vitro culture after inhibition, while spindle checkpoint-dependent meiosis was also delayed. Mitochondrial Ca2+ levels changed, and this was followed by altered mitochondrial masses and ATP levels within oocytes during the entirety of meiosis progression. Abnormal mitochondrial Ca2+ concentrations in oocytes then hindered meiotic progress and activated AMP-activated protein kinase (AMPK) signalling that is associated with gene expression. Conclusions: These data provide new insight into the protective role that MCU-dependent mitochondrial Ca2+ signalling plays in meiotic progress, in addition to demonstrating a new mechanism of mitochondrial energy regulation by AMPK signalling that influences meiotic maturation.