Tuba1a is uniquely important for axon guidance through midline commissural structures

Developing neurons undergo dramatic morphological changes to appropriately migrate and extend axons to make synaptic connections. The microtubule cytoskeleton, made of α/β-tubulin dimers, drives neurite outgrowth, promotes neuronal growth cone responses, and facilitates intracellular transport of critical cargoes during neurodevelopment. constitutes the majority of α-tubulin in the developing brain and mutations to in humans cause severe brain malformations accompanied by varying neurological defects, collectively termed tubulinopathies. Studies of function have been limited by the presence of multiple genes encoding highly similar tubulin proteins, which prevents TUBA1A-specific antibody generation and makes genetic manipulation challenging. Here we present a novel tagging method for studying and manipulating in cells without impairing tubulin function. Using this tool, we show that a loss-of-function mutation (), reduced the amount of TUBA1A protein and prevented incorporation of TUBA1A into microtubule polymers. Reduced Tuba1a α-tubulin in heterozygous mice significantly impacted axon extension and impaired formation of forebrain commissures. Neurons with reduced Tuba1a caused by had altered microtubule dynamics and slower neuron outgrowth compared to controls. Neurons deficient in Tuba1a failed to localize microtubule associated protein-1b (Map1b) to the developing growth cone, likely impacting reception of developmental guidance cues. Overall, we show that reduced Tuba1a is sufficient to support neuronal migration, but not axon guidance, and provide mechanistic insight as to how tunes microtubule function to support neurodevelopment.