In vivo timelapse imaging and analysis of Golgi satellite organelle distribution and movement in the neural progenitor cells of the brain

The dividing stem cells of the developing brain are the radial glial neural progenitor cells (NPCs), multifunctional cells that proliferate to generate all of the cells of the brain, but also act as scaffolds for their migrating neuron progeny, guideposts for pathfinding growing axons and regulators of synaptic activity. These remarkable cells perform these very different activities while remaining in contact with the inner and outer surface of the ever-growing brain. NPCs synthesize proteins locally to support the compartmentalized protein expression required for the cells to perform their specialized functions, but it is not clear how the necessary processing that normally occurs in the Golgi apparatus is achieved at locations far from the cell body. Golgi satellites, motile organelles and members of the protein maturation machinery, control protein glycosylation and maturation in polarized cells like neurons. To investigate whether NPCs also rely on Golgi satellites, we expressed a fluorescent reporter to label Golgi satellites in the NPCs in the intact brains of Xenopus laevis tadpoles. Quantitative analysis of in vivo timelapse images revealed dynamic, motile Golgi satellites that distribute throughout the cell, suggesting that NPCs have local proteostasis to support their diverse functions.