Some aspects of energy coupling by mitochondria

Neuronal mitochondrial calcium uniporter deficiency exacerbates axonal injury and suppresses remyelination in mice subjected to experimental autoimmune encephalomyelitis

High-capacity mitochondrial calcium (Ca²⁺) uptake by the mitochondrial Ca²⁺ uniporter (MCU) is strategically positioned to support the survival and remyelination of axons in multiple sclerosis (MS) by undocking mitochondria, buffering Ca²⁺ and elevating adenosine triphosphate (ATP) synthesis at metabolically stressed sites. Respiratory chain deficits in MS are proposed to metabolically compromise axon survival and remyelination by suppressing MCU activity. In support of this hypothesis, clinical scores, mitochondrial dysfunction, myelin loss, axon damage and inflammation were elevated while remyelination was blocked in neuronal MCU deficient (Thy1-MCU Def) mice relative to Thy1 controls subjected to experimental autoimmune encephalomyelitis (EAE). At the first sign of walking deficits, mitochondria in EAE/Thy1 axons showed signs of activation. By contrast, cytoskeletal damage, fragmented mitochondria and large autophagosomes were seen in EAE/Thy1-MCU Def axons. As EAE severity increased, EAE/Thy1 axons were filled with massively swollen mitochondria with damaged cristae while EAE/Thy1-MCU Def axons were riddled with late autophagosomes. ATP concentrations and mitochondrial gene expression were suppressed while calpain activity, autophagy-related gene mRNA levels and autophagosome marker (LC3) co-localization in Thy1-expressing neurons were elevated in the spinal cords of EAE/Thy1-MCU Def compared to EAE/Thy1 mice. These findings suggest that MCU inhibition contributes to axonal damage that drives MS progression.

Advances in measuring cellular bioenergetics using extracellular flux

Cell-based assays have become a favored format for drug discovery because living cells have relevant biological complexity and can be highly multiplexed to screen for drugs and their mechanisms. In response to a changing extracellular environment, disease and/or drug exposure, cells remodel bioenergetic pathways in a matter of minutes to drive phenotypic changes associated with these perturbations. By measuring the extracellular flux (XF), that is the changes in oxygen and proton concentrations in the media surrounding cells, one can simultaneously determine their relative state of aerobic and glycolytic metabolism, respectively. In addition, XF is time-resolved and non-invasive, making it an attractive format for studying drug effects in vitro.

The genetical history of humans and the great apes

When and where did modern humans evolve? How did our ancestors spread over the world? Traditionally, answers to questions such as these have been sought in historical, archaeological, and fossil records. However, increasingly genetic data provide information about the evolution of our species. In this review, we focus on the comparison of the variation in the human gene pool to that of our closest evolutionary relatives, the great apes, because this provides a relevant perspective on human genetical evolution. For instance, comparisons to the great apes show that humans are unique in having little genetic variation as well as little genetic structure in their gene pool. Furthermore, genetic data indicate that humans, but not the great apes, have experienced a period of dramatic growth in their early history.