RAB6 and dynein transport prevents neuronal progenitor delamination
The development of fast subcellular live imaging within thick samples enabled us to address the long-standing question of how polarized trafficking is regulated in aRG cells. In particular, we revealed how transmembrane cargos are transported from the perinuclear area, where the Endoplasmic reticulum and Golgi are localized, to the apical surface of these cells (Brault et al, Embo Reports, 2022). Post-Golgi trafficking had been extensively studied in 2D non-polarized cells, and had been shown to be dependent on plus end-directed kinesins. Using live imaging of post-Golgi RAB6+ vesicles, we showed here that apical trafficking was dependent on the minus end directed dynein and its partner LIS1, indicating that in polarized epithelial cells such as aRG cells, the polarity of motors is completely inverted. In RG cells, we showed that the RAB6-dynein-LIS1 pathway was required for transport to the apical surface of Crumbs, a major regulator of epithelial polarity. Genetic ablation of LIS1 or double knock-out of RAB6A and brain-specific RAB6B (that we generated for this study), all led to an impairment of Crumbs localization at the apical surface and, as a consequence, to a loss of apical junctions. This led to a delamination of aRG cells, observed using live imaging. Detached aRG cells were aberrantly localized basally and continued to proliferate. This work therefore highlights an important molecular mechanism for the delamination of aRG cells, which in human is at the basis of the production of bRG cells.
Post-Golgi apical transport of Crumbs is driven by dynein in aRG cells
RUSH assay for CRB3-GFP in control (mcherry) and dynactin-inhibited radial glial cells (CC1-p150-dsRed), electroporated at E.15.5 and imaged at E16.5. CRB3 is retained in the endoplasmic reticulum until the addition of biotin, which releases it for trafficking. Upon dynein/dynactin inhibition, Crumbs fails to reach the apical surface. SBP: Streptavidin-binding protein. St: Streptavidin. Scale bar = 5µm.
Brault J.B., Bardin S., Lampic M., Carpentieri J.A., Coquand L., Penisson M., Lachuer H., Victoria G.S., Baloul S., El Marjou F., Boncompain G., Miserey-Lenkei S., Belvindrah R., Fraisier V, Francis F., Perez F., Goud B., Baffet AD (2022) RAB6 and dynein drive post-Golgi apical transport to prevent neuronal progenitor delamination. EMBO Rep. Aug 18:e54605