Phospholipid biogenesis maintains neuronal integrity during aging and axon regeneration

Neurons maintain their morphology over prolonged periods of adult life with limited regenerative capacity. Among the various factors that shape neuronal morphology, lipids function as membrane components, signaling molecules, and regulators of synaptic plasticity. Here, we tested genes involved in phospholipid biosynthesis and identified their roles in axon regrowth and maintenance. CEPT-2 and EPT-1 are enzymes catalyzing the final steps in the de novo phospholipid synthesis (Kennedy) pathway. Loss of function mutants of cept-2 or ept-1 show reduced axon regrowth and failure to maintain axon morphology. We demonstrate that CEPT-2 is required cell-autonomously to prevent age-related axonal morphology defects. We further investigated genetic interactions of cept-2 or ept-1 with dip-2, a conserved regulator of lipid metabolism that affects axon morphology maintenance and regrowth after injury. Loss-of-function in dip-2 led to suppression of axon regrowth defects observed in either cept-2 or ept-2 mutants, suggesting that DIP-2 acts to counterbalance phospholipid synthesis. Our findings reveal the genetic regulation of lipid metabolism as critical for axon maintenance following injury and during aging.