Valdebenito, G. E. | Search bioRxiv

bioRxiv2026

A genetically encoded redox bottleneck constrains human developmental rate

The intrinsically slow pace of human development poses challenges for regenerative medicine and disease modeling. This trait is attributed to low metabolic rates, yet the endogenous mechanisms determining species-specific metabolic flux remain unknown. Here, we identify coupling between glycolytic NADH production and mitochondrial oxidation through the glycerol-3-phosphate (G3P) shuttle as a genetic bottleneck constraining human developmental tempo. Using stem cell-derived models of the segmentation clock, an oscillator whose period reflects developmental rate, we show that low expression of the G3P shuttle enzyme GPD1L limits NADH oxidation in human progenitors compared to mouse. Overexpressing GPD1L boosts metabolic flux, accelerating the segmentation clock, cell cycle, and differentiation across germ layers. G3P-mediated redox coupling is thus a genetically encoded, rate-limiting mechanism that sets the tempo of human development.

developmental biology↗

bioRxiv2024

Metabolic remodelling in hiPSC-derived myofibres carrying the m.3243A>G mutation

Mutations in mitochondrial DNA cause severe multisystem disease, frequently associated with muscle weakness. The m.3243A>G mutation is the major cause of Mitochondrial Encephalomyopathy Lactic Acidosis and Stroke Like episodes (MELAS). Experimental models that recapitulate the disease phenotype in vitro for disease modelling or drug screening are very limited. We have therefore generated hiPSC-derived muscle fibres with variable heteroplasmic mtDNA mutation load without significantly affecting muscle differentiation potential. The cells are excitable and show physiological characteristics of muscle fibres and show well organised myofibrillar structure. In cells carrying the m.3243A>G, the mitochondrial membrane potential and oxygen consumption were reduced in relation to the mutant load. We have shown through proteomic, phosphoproteomic, and metabolomic analyses that the m.3243A>G mutation variably affects the cell phenotype in relation to the mutant load. This variation is reflected by an increase in the NADH/NAD+ ratio, which in turns influences key nutrient-sensing pathways in the myofibres. This model enables detailed study of the impact of the mutation on cellular bioenergetics and on muscle physiology with the potential to provide a platform for drug screening.

cell biology↗