Biology subjects

Piasecki, A. J.

Publications and source records attributed to Piasecki, A. J..

2 recordsLinked to original sources

bioRxiv2026

Mitochondrial subpopulations in oocytes and cumulus cells exhibit distinct age-associated changes and selective plasticity in response to NMN supplementation

BackgroundMitochondrial dysfunction is a leading contributor to the decline in oocyte quality associated with maternal aging. Prior investigations of mitochondrial function in the ovarian follicle have largely treated the mitochondrial pool as a homogeneous population, reporting aggregate values that may obscure biologically meaningful differences between distinct mitochondrial subpopulations. The present study addresses this limitation by characterizing mitochondrial subpopulation dynamics in oocytes and cumulus granulosa cells at single-organelle resolution using fluorescence-activated mitochondria sorting (FAMS). ResultsAnalysis of the aggregate mitochondrial population in mouse oocytes revealed no significant age-associated differences in mitochondrial DNA copy number or membrane potential, a result that would previously have been interpreted as evidence of minimal age-related mitochondrial change. Subpopulation analysis revealed this conclusion to be incomplete: aged oocytes showed significantly elevated mitochondrial DNA copy number specifically within the high membrane potential and small mitochondrial subpopulations, with no significant differences in the low membrane potential or large subpopulations. NMN supplementation normalized mitochondrial DNA copy number in the high membrane potential and small subpopulations toward young levels while producing an opposing effect in large mitochondria, demonstrating subpopulation-specific rather than uniform rejuvenation. In cumulus cells, significant age-associated changes were detectable at the aggregate level, including a reduction in mitochondrial DNA copy number and an elevation in membrane potential, and subpopulation analysis further resolved these findings. The age-associated reduction in cumulus cell mitochondrial DNA copy number was driven predominantly by the high membrane potential subpopulation. NMN supplementation exerted opposing effects on small and large cumulus cell mitochondrial subpopulations, increasing mitochondrial DNA copy number above both young and aged levels in small mitochondria while further reducing it below aged levels in large mitochondria. ConclusionsViewing the mitochondrial pool as a heterogeneous mixture of functionally distinct subpopulations rather than a uniform population reveals age-associated alterations in oocytes and cumulus cells that are undetectable by aggregate analysis. NMN supplementation exerts subpopulation-specific effects in both cell types, identifying specific mitochondrial subtypes as more precise targets for future mechanistic investigation of age-associated infertility than the mitochondrial pool considered in aggregate.

developmental biology↗

bioRxiv2026

Mitochondria-Associated Transcription Precedes Oxidative Phosphorylation Activation During Human Pre-Implantation Embryogenesis

Mitochondria undergo significant structural and functional changes during human pre-implantation embryogenesis, yet the transcriptional activity of both nuclear-encoded mitochondria-associated genes and mitochondrially transcribed genes across this developmental window remains poorly characterized. While mitochondria are established as the primary energy source for the early embryo, emerging evidence suggests they may also influence lineage specification through epigenetic regulation and metabolite availability. To investigate this, we reanalyzed two publicly available human single-cell RNA sequencing datasets filtered for mitochondria-associated genes using the MitoCarta 3.0 reference database, with separate analyses conducted on the nuclear-encoded and mitochondrially transcribed subsets. The first dataset spanned individual blastomeres from the oocyte through blastocyst stage, and the second compared trophectoderm and inner cell mass cells isolated from blastocysts. Mitochondria-associated gene expression was sufficient to cluster human blastomeres by developmental stage, with morula and blastocyst stage cells forming well-defined clusters. Mitochondrially transcribed genes were found to be the primary drivers of clustering in earlier developmental stages, while nuclear-encoded mitochondria-associated genes drove clustering at the blastocyst stage. A pronounced shift in the expression of both gene sets was identified at the transition from the 4-cell to the 8-cell stage, with 115 unique differentially expressed genes identified across the two stages immediately following this transition, compared to only 5 across the two prior stages. The timing of this transcriptional upregulation, preceding the known onset of oxidative phosphorylation at approximately the 32-cell stage, suggests a mitochondrial role in early embryogenesis beyond energy production. Analysis of trophectoderm and inner cell mass cells showed that mitochondrial gene expression profiles partially distinguished these two lineages, consistent with known differences in mitochondrial activity between them. These findings suggest that both nuclear-encoded and mitochondrially transcribed gene expression is upregulated prior to the first lineage specification event in the human embryo, potentially contributing to epigenetic regulation and cell fate determination through altered metabolite availability. A limitation of this study is its reliance on transcriptomic data alone; future work incorporating functional metabolite measurements will be needed to establish causality. Nonetheless, these data reframe mitochondria as active participants in early human developmental programming rather than passive energy suppliers.

developmental biology↗