Biology subjects

Sawai, A.

Publications and source records attributed to Sawai, A..

4 recordsLinked to original sources

bioRxiv2026

PHC2-Dependent PRC1 Assemblies Stabilize Motor Neuron Hox Codes

Polycomb Repressive Complexes PRC1 and PRC2 establish and maintain chromatin architectures critical for cell-type specific gene expression. In the developing spinal cord, PRC1 is essential for implementing Hox-dependent transcriptional programs that diversify motor neuron identities. Although PRC1 can assemble into subnuclear condensates, whether these structures contribute to the specification and maintenance of neuronal subtype fates remains unclear. Using chick and mouse models, we show that canonical PRC1 components - BMI1, PHC2, CBX2, RING1B - coalesce into subnuclear assemblies as neural progenitors differentiate into motor neurons. Disrupting PHC2 polymerization in either neural progenitors or postmitotic neurons dismantles BMI1-containing PRC1 assemblies, triggering derepression of caudal Hox genes and a cell autonomous loss of segment-specific motor neuron fates. Mouse mutants lacking the core PRC1 subunit Ring1 fail to form BMI1-containing assemblies, despite intact PHC2 and CBX2 polymers. In contrast, motor neuron-restricted deletion of core PRC2 subunits (Ezh1/2) depletes H3K27me3 histone marks but retains PRC1 assemblies and Hox boundaries. Together, these findings indicate that PHC2-dependent PRC1 assemblies stabilize Hox transcriptional boundaries and motor neuron segmental identities.

developmental biology↗

bioRxiv2025

Conserved metabolic adaptation mechanisms in cancer cells and yeast against mitochondrial dysfunction indicate an additional role of aerobic glycolysis for cell survival

Eukaryotic cells primarily generate ATP through oxidative phosphorylation and substrate-level phosphorylation. Despite the superior efficiency of oxidative phosphorylation, eukaryotic cells often utilize both pathways as aerobic glycolysis even in the presence of oxygen. However, its role in cell survival remains poorly understood. In this study, aerobic glycolysis of the Warburg effect in breast cancer cells (MCF7) and the Crabtree effect in a laboratory strain of Saccharomyces cerevisiae (S288C) were compared following treatment with electron transport chain inhibitors, including FCCP, antimycin A, and oligomycin. MCF7 and S288C exhibited strikingly similar metabolic rewiring toward substrate-level phosphorylation against the inhibitor treatment, suggesting that mitochondrial oxidative phosphorylation and cytosolic substrate-level phosphorylation communicate through a common mechanism. Measurements of mitochondrial membrane potential (MMP) and ATP concentration further indicated that cytosolic ATP was transported into the mitochondria under conditions of reduced electron transport chain activity. This ATP was likely utilized by the reverse mode of H+/ATPase to maintain the MMP which contributed to avoiding programmed cell death. These results suggest that the ATP supply to mitochondria plays a conserved role in aerobic glycolysis across yeast and mammalian cancer cells. This mechanism likely contributes to cell survival under conditions of fluctuating oxygen availability.

cell biology↗

bioRxiv2021

Aerobic glycolysis in cancer cells supplies ATP while preventing excess metabolic thermogenesis

Adenosine triphosphate (ATP) regeneration by substrate-level phosphorylation is a general feature of cancer metabolism, even under normoxic conditions (aerobic glycolysis). However, it is unclear why cancer cells prefer inefficient aerobic glycolysis over the highly efficient process of oxidative phosphorylation for ATP regeneration. To investigate the metabolic principles underlying aerobic glycolysis, we performed 13C-metabolic flux analysis of 12 cultured cancer cell lines and explored the metabolic constraints required to reproduce the results using in silico metabolic simulations. We found that the measured flux distribution can be reproduced by maximizing the ATP consumption in the flux balance analysis considering a limitation of metabolic heat dissipation (enthalpy change). It suggests that aerobic glycolysis may be preferable because metabolic heat production during one mol of ATP regeneration by aerobic glycolysis was less than that produced by oxidative phosphorylation (OXPHOS). Consistent with the simulation, OXPHOS inhibition induced metabolic redirection to aerobic glycolysis while maintaining the intracellular temperature. Furthermore, the dependency on aerobic glycolysis was partly alleviated upon culturing at low temperatures. Our data suggest that metabolic thermogenesis is an important factor in understanding aerobic glycolysis in cancer cells and that an advantage of aerobic glycolysis is the reduction in metabolic heat generation during ATP regeneration.

cancer biology↗

bioRxiv2021

PRC1 Sustains the Memory of Neuronal Fate Independent of PRC2 Function

Polycomb repressive complexes (PRCs) 1 and 2 maintain stable cellular memories of early fate decisions by establishing heritable patterns of gene repression. PRCs repress transcription through histone modifications and chromatin compaction, but their roles in neuronal subtype diversification are poorly defined. We unexpectedly found that PRC2 is dispensable to preserve the morphogen-induced positional fates of spinal motor neurons (MNs), while PRC1 is essential for the specification of segmentally-restricted subtypes. Mutation of the core PRC1 component Ring1 in mice leads to increased chromatin accessibility and ectopic expression of a broad variety of fates determinants, including Hox transcription factors, while neuronal class-specific features are maintained. Loss of MN subtype identities in Ring1 mutants is due to the suppression of Hox networks by derepressed caudal Hox genes. These results indicate that PRC1 can function independently of de novo PRC2-dependent histone methylation to maintain chromatin topology and transcriptional memory at the time of neuronal differentiation.

neuroscience↗