Non-canonical features of the Golgi apparatus in bipolar epithelial neural stem cells

Abstract

Apical radial glia (aRG), the stem cells in developing neocortex, are unique bipolar epithelial cells, extending an apical process to the ventricle and a basal process to the basal lamina. Here, we report novel features of the Golgi apparatus, a central organelle for cell polarity, in mouse aRGs. The Golgi was confined to the apical process but not associated with apical centrosome(s). In contrast, in aRG-derived, delaminating basal progenitors that lose apical polarity, the Golgi became pericentrosomal. The aRG Golgi underwent evolutionarily conserved, accordion-like compression and extension concomitant with cell cycle-dependent nuclear migration. Importantly, in line with endoplasmic reticulum but not Golgi being present in the aRG basal process, its plasma membrane contained glycans lacking Golgi processing, consistent with direct ER-to-cell surface membrane traffic. Our study reveals hitherto unknown complexity of neural stem cell polarity, differential Golgi contribution to their specific architecture, and fundamental Golgi re-organization upon cell fate change.

The polarity and properties of radial glia‐like neural stem cells are altered by seizures with status epilepticus: Study using an improved mouse pilocarpine model of epilepsy

“…The formation of cell processes, such as neurites, and the establishment of cell polarity are closely associated with microtubule organization that takes place at the microtubule‐organizing center, including the centrosome, located at the base of cell processes (Taverna et al, ; Wiese & Zheng, ). To confirm the polarity changes of RGL cells, the expression of γ‐tubulin, a centrosome marker (Taverna et al, ; Wiese & Zheng, ) was analyzed in Gfap ‐GFP+/S100β− cells at 10 days after pilocarpine injection. The angle α between the nucleus‐centrosome axis (centrosomes were visualized as γ‐tubulin+ puncta) and the inferior border of the GCL was measured (Figure a).…”

Moving messages in the developing brain—emerging roles for mRNA transport and local translation in neural stem cells

“…Indeed whether a given transcript is translated could be related to a number of factors including mRNA reporter, RGC cell cycle stage, developmental stage, or signals emanating from surrounding niche. Beyond local translation at endfeet, it is interesting to consider that within basal processes, translation ‘hot spots’ may also exist, as suggested by a recent study which showed ER are scattered along the basal process .…”

“…The FMRP interactome at basal endfeet also contains some mRNAs encoding membrane and secreted proteins. However, use of both EM and fluorescent proteins marking Golgi components, indicate that RGC basal processes and endfeet lack conventional golgi apparatus, as do neuronal axons . This raises the question of how some locally translated proteins are appropriately modified in the absence of Golgi.…”

“…This structure provides a guidepost for excitatory neurons to migrate from their birthplace in the germinal zones to their final destination in the cortical plate. EM studies together with immunolabeling reveal that organelles are subcellularly localized within RGCs—with Golgi found only within the cell body, and endoplasmic reticulum (ER) distributed throughout the cell body and radial fibers . RGC cell bodies form distinct interconnected clusters linked by Gap junctions, through which calcium signaling can propagate .…”

Coupling progenitor and neuronal diversity in the developing neocortex

“…Being highly polarized, these cells also display asymmetric localization of cellular processes, cellular components and molecules. For example, the Golgi apparatus are preferentially localised at the apical process, while the endoplasmic reticulum is localised in both the apical and basal processes .…”