Contents

March 2020
Vol 6, Issue 11

About The Cover

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ONLINE COVER Programmed cell death—in which unnecessary extra neurons are destroyed during neurodevelopment—typically limits the number of available neurons in the brain. Previous research suggests nervous systems evolve through surges in the number of available neurons, which enable higher sensitivity to signals from the environment. To explore how disrupting programmed cell death may result in a surplus of neurons that can boost a fruit fly's smell sensory system, Prieto-Godino et al. worked with flies missing a cluster of genes critical for the usual neuron death wave to occur. They labeled the designated survivors with a fluorescent marker, observing higher numbers of labeled cells in the mutant flies than in those experiencing usual programmed cell death. These cells integrated seamlessly with the brain's existing smell sensory system, displaying different properties than neurons never slated to die. The findings reveal the hidden evolutionary potential of ill-fated neurons, suggesting they may represent a reserve through which novel neuron types and neural circuits may evolve over time. Future research may explain how, precisely, shifts in this cellular process combine with other genetic changes to form new olfactory pathways. [CREDIT: EYE OF SCIENCE/SCIENCE SOURCE]