Article Abstract:
The neural activity-dependent and activity-independent mechanisms that generate precision of neuronal connections during development are reviewed. These two mechanisms act in concert to regulate the formation of precise patterns of neural connections. Activity-independent mechanisms usually operate during pathway and target recognition, while activity-dependent mechanisms are responsible for the refinement and remodelling of these initial coarse patterns of synaptic connections. These mechanisms are illustrated by comparing and contrasting the connections between motoneurons and muscles and between the thalamus and cortex.
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Article Abstract:
The glial cells missing (gcm) gene in Drosophila functions as a genetic switch during the development of the glia cells and neurons of the central and peripheral nervous system. If the gcm protein is present presumptive neurons form glia, but if the protein is absent some presumptive glia form neurons. In mutants where gcm is non-functional, almost all the glia fail to differentiate and form neurons instead. The expression of ectopic gcm expression in these mutants with the help of transgenic vectors makes some presumptive neurons differentiate into glia instead.
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Article Abstract:
The basis for the ability of motor axons to connect with appropriate muscles in Drosophila is investigated using ablation analysis of adhesion molecules in this insect. Results reveal that there are particular cell adhesion molecules that either repel or attract axons. The axons do not react to particular signalling molecules but to the total signal in a particular muscle before innervating it or connecting with other muscles.
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