Effects of mutating α-tubulin lysine 40 on sensory dendrite development

Microtubules are essential to neuronal structure and function. Axonal and dendritic microtubules are enriched in post-translational modifications that impact microtubule dynamics, transport, and microtubule-associated proteins. Acetylation of -tubulin lysine 40 (K40) is a prominent, conserved modification of neuronal microtubules. However, the cellular role of microtubule acetylation remains controversial. To resolve how microtubule acetylation might affect neuronal morphogenesis we mutated endogenous -tubulin in vivo using a new fly strain that facilitates the rapid knock-in of designer -tubulin alleles. Leveraging our new strain, we found that microtubule acetylation, as well as polyglutamylation and (de)tyrosination, is not essential for survival. However, we found that dendrite branch refinement in sensory neurons relies on -tubulin K40. Mutagenesis of K40 reveals moderate yet significant changes in dendritic lysosome transport, microtubule polymerization, and Futsch distribution in dendrites but not axons. Our studies point to an unappreciated role for -tubulin K40 and acetylation in dendrite morphogenesis. While our results are consistent with the idea that microtubule acetylation patterns microtubule function within neurons, they also suggest there may be a structural requirement for -tubulin K40.\n\nSummary StatementNeurons are enriched in post-translationally modified microtubules. Targeted mutagenesis of endogenous -tubulin in flies reveals that dendrite branch refinement is altered by acetylation-blocking mutations.