Centriole Loss in Embryonic Development Disrupts Axonal Pathfinding and Muscle Integrity

Centrosomes, the primary microtubule-organizing centers (MTOCs), are crucial for early neuronal development, particularly in establishing polarity and promoting axon formation. Traditionally considered non-essential in terminally differentiated cells, recent evidence suggests that centrosomes play vital roles in specialized cellular contexts. In mammalian neurons, centrosome-mediated microtubule remodeling is essential for axon elongation, with centrosome dysfunction leading to axonal misrouting and growth defects. Although active centrosomes have been detected in the tracheal terminal cells of Drosophila melanogaster , their activity in neurons in vivo has not been observed. Their gradual loss during embryogenesis has been reported as non-essential for organogenesis, as adult flies can eclose without centrioles.

To investigate centrosome activity in neurons, we revisited Drosophila Sas-4 mutants, which exhibit centrosome loss (CL), and observed that 50% of homozygous mutant individuals fail to hatch as larvae. We analysed their development, focusing on the expressivity and penetrance of nervous system phenotypes, and examined centriole localization in neurons. Our findings confirm the presence of centrosomes in motor and sensory neurons in Drosophila and their localization near the nascent axon. CL conditions resulted in axonal misrouting and muscle developmental abnormalities. Targeted downregulation of Sas-4 in the pioneer motor neurons aCC and RP2 induced axon guidance errors, indicating an autonomous role for centrosomes in axonal navigation. Colocalization of acetylated- and γ-tubulin with centrioles in motor neurons further confirmed the presence of functional centrosomes in these cells. Analysis of motor axons revealed that CL leads to axonal tortuosity, a characteristic associated with neurodegeneration. This is the first direct association of CL with axonal morphological phenotypes, highlighting the role of centrosomes in neuronal development and their broader influence on nervous system structure and function.