The role of wrapping glia cells in radial axonal growth
Increased nerve conduction velocity enables a fast computation between sensory stimuli and behavioral output, thereby facilitating the interaction between an animal and its external environment. Besides other mechanisms nerve conduction velocity can be increased by a growth in axon diameter, which decreases the internal resistance of the axon promoting the propagation of action potentials. In vertebrates an increase in axon diameter is strongly correlated with the association of the axon with glia cell. For example, the formation of myelin around an axon promotes the phosphorylation of neurofilaments which increases the axonal diameter. It is further assumed that axon associated glia cells provide metabolic support to the axon which could also contribute to an increase in axon diameter. However, small diameter axons and especially axons of invertebrates like Drosophila melanogaster completely lack neurofilaments and knowledge about the contribution of Drosophila glia cells to radial axonal growth is still sparsely documented.
During my PhD I want to address the question if wrapping glia cells, that resemble the ensheathing type of glia cell within the peripheral nervous system of the Drosophila larvae, contribute to radial axonal growth. Further, I want gain insights into how these two cell types communicate in this important mechanism that finally leads to an increased processing speed of the whole larval nervous system. To do so I interfere with glial and neuronal function and subsequently examine the effects on the axonal diameter using the electron microscope.