Seminars

Microtubules (MTs) are fundamental for a wide range of developmental processes such as cell division, polarization, migration, differentiation and growth. MTs are classified into two major categories, centrosomal and non-centrosomal. Non-centrosomal MTs emanate from sites other than the centrosome, such as the Golgi apparatus, nuclear envelope and apical cortex. Although general functions of MTs in developmental processes have been well studied, specific roles of non-centrosomal MT subsets have been less known. However, the recent discovery of CAMSAP/Nezha/Patronin family proteins that are responsible for assembly of non-centrosomal MTs opened the way to exploring roles of non-centrosomal MTs in developmental processes. In the seminar, I will talk about how the CAMSAP3-non-centrosomal MT subset defines the ventricular shape of the brain. CAMSAP3 is preferentially expressed in ependymal cells, which line the ventricular wall. Using CAMSAP3 mutant mice where its function is abolished, we found that CAMSAP3 supports mTORC1 signaling and thereby the growth of ependymal cells, possibly through control of MT-dependent lysosomal positioning. Loss of this mechanism inhibits the normal expansion of the ventricle cavities, leading to the narrowing and closure of the lateral ventricles and associated loss of adult neural stem cells from the niche along the ventricular wall. These observations suggest that the CAMSAP3–non-centrosomal MT system is indispensable for constructing robust lateral ventricles, which support brain homeostasis.