How does alternate splicing of a sodium channel gene generate diversity in neuronal signalling?

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The human brain contains a staggeringly large number of nerve cells (neurons) that form networks of connections (synapses) with one another. These neuronal circuits control almost everything we do, including behaviours such as breathing, walking and learning. Diversity of behaviour is mirrored by the need for a similar degree of diversity of function of individual nerve cells. Thus, neurons differ in the target that they contact, the signalling chemicals (neurotransmitters) they release, and the way in which they are able to fire electrical action potentials that trigger release of their neurotransmitter(s). Indeed, the degree of diversity of these characteristics is likely orders of magnitude greater than the number of genes present in the genome and, as such, additional mechanisms are required. Recent research suggests that additional diversity is due, at least in part, to different protein products being produced from the same genes. Alternate splicing, as this is called, results in multiple related proteins being encoded within one gene. Each protein variant produced has the capability of conferring different properties to the neuron in which expression occurs. Although now established, it remains largely to be shown how splicing induces changes to neuron function. We use the fruitfly because it is very amenable to genetic analysis, the complete genome has been sequenced, and because it provides a simple model of the human nervous system. Our study will inform us how our own nerve cells are able to develop to have different properties from one another.