The AMPK-related kinase NUAK1 controls cortical axons branching though a local modulation of mitochondrial metabolic functions
The precise regulation of the cellular mechanisms underlying axonal morphogenesis is essential to the formation of functional neuronal networks. We previously identified the autism-candidate kinase NUAK1 as a central regulator of axon branching in mouse cortical neurons through the control of mitochondria trafficking. How does local mitochondrial position or function regulate axon branching during development? Here, we characterized the metabolic regulation in the developing axon and report a marked metabolic decorrelation between axon elongation and collateral branching. We next solved the cascade of event leading to presynaptic clustering and mitochondria recruitment during spontaneous branch formation. Interestingly and contrary to peripheral neurons, mitochondria are recruited after but not prior to branch formation in cortical neurons. Using flux metabolomics and fluorescent biosensors, we observed that NUAK1 deficiency significantly impairs mitochondrial metabolism and axonal ATP concentration. Upregulation of mitochondrial function is sufficient to rescue axonal branching in NUAK1 null neurons in vitro and in vivo. Altogether, our results indicate that NUAK1 exerts a dual function during axon branching through its ability to control mitochondria distribution and activity, and suggest that a mitochondrial-dependent remodeling of local metabolic homeostasis plays a critical role during axon morphogenesis.