Autophagy is required for dopaminergic axon development and confers their responsiveness to guidance cues.

Midbrain dopamine (mDA) neurons play a wide range of brain functions, but the molecular mechanisms driving the formation of mDA circuits remain largely unknown. Here, we show that autophagy, the main cellular recycling pathway, is present in the growth cones of developing mDA neurons, and its level changes dynamically in response to guidance cues. To characterize the role of autophagy in mDA axon growth and guidance, we knocked out essential autophagy genes (Atg12, Atg5) specifically in mDA neurons in mice of either sex. Autophagy-deficient mDA axons exhibit axonal swellings and reduced branching both in vitro and in vivo. Strikingly, deletion of autophagy-related genes completely blunted the response of mDA neurons to both chemorepulsive and chemoattractive guidance cues. Our data demonstrate that autophagy plays a central role in regulating mDA neuron development by orchestrating axonal growth and guidance. Significance Statement Midbrain dopaminergic neurons form circuits essential for movement, motivation, and cognition, yet the intracellular mechanisms controlling their axon growth and guidance remain poorly understood. Here we show that autophagy, a major cellular recycling pathway, operates locally in dopaminergic growth cones and is dynamically regulated by guidance cues. Using neuron-specific deletion of core autophagy genes, we demonstrate that autophagy is required for proper axonal morphology, branching, and responsiveness to both chemoattractive and chemorepulsive signals. These findings identify autophagy as a key regulator of dopaminergic circuit formation and reveal a previously unrecognized mechanism linking intracellular degradation pathways to axon guidance during brain development.