The mRNA decay factor CAR-1 regulates axon regeneration via mitochondrial calcium dynamics

mRNA decay factors regulate mRNA turnover by recruiting non-translating mRNAs and targeting them for degradation, yet it remains poorly understood how mRNA decay factors function in vivo to regulate specific cellular processes. Here we show that mRNA decay factors form cytoplasmic puncta in C. elegans neurons and have opposing roles in axon maintenance and regrowth. While the decapping enzymes DCAP-1/DCP1 and DCAP-2/DCP2 regulate developmental axon guidance and promote axon regrowth upon injury, the translational repressors CAR-1/LSM14 and CGH-1/DDX6 regulate axon maintenance and inhibit axon regrowth in adult animals. We identified mRNA targets of CAR-1 in neurons and found that the mitochondrial calcium uptake regulator micu-1 is repressed by CAR-1. We show that axon injury triggers a transient mitochondrial calcium influx via the MCU-1 uniporter that is more sustained in car-1 loss of function mutants. The enhanced axon regrowth and defective axon maintenance of car-1 mutants are dependent on MICU-1 function. Our results uncover specific roles for mRNA decay regulators in neurons and reveal a novel pathway that controls axon regrowth through mitochondrial calcium uptake. seCLIP-seq in C. elegans strains CZ25180 and CZ26430