Microcephaly gene Cenpj regulates axonal growth in cortical neurons through microtubule destabilization.

Neocortex development comprises of a complex series of time- and space-specific processes to generate the typical interconnected six-layered architecture of adult mammals. Axon growth is required for the proper establishment of cortical circuits. Malformations in axonal growth and pathfinding might lead to severe neuropathologies, such as corpus callosum dysgenesis. Cenpj, a microcephaly gene, encodes a scaffold protein that regulates centrosome biogenesis and microtubule stabilization. During corticogenesis, Cenpj regulates progenitor division and neuronal migration. Since microtubule stabilization is crucial for axon extension, we investigated the role of Cenpj in axon growth during cortical development in a mouse model. Through loss- and gain-of-function assays ex vivo and in utero, we quantified callosal axonal length, branching, and growth cone size compared to controls. We observed that silencing Cenpj results in an increased axonal length. Ex vivo, we assessed the number of branches, the area of growth cones and the stability of microtubules. In silenced Cenpj axons, there were more branches, larger growth cone area, and more stable microtubules. Rescue experiments confirmed that neurons present axonal length comparable to controls. Here we propose that Cenpj regulates axon growth by destabilizing microtubules during cortical development. Finally, our findings suggest that Cenpj might be a novel target for axonal regeneration.