Expression of neurexin Iα splice variants in sympathetic neurons:: Selective changes during differentiation and in response to neurotrophins

Neurexins are a surprisingly diverse group of alternatively spliced proteins possibly involved in neural cell recognition processes. We find neurexin I alpha and its splice variants highly conserved between mammals and birds. In vivo, neurexin I alpha is expressed in sympathetic neurons during target innervation and relative expression levels of splice variants change with development. In vitro, no such changes are observed in the absence of growth factors, indicating that interactions with the environment are required to modify the splicing pattern. Specific alterations in splice variant expression are induced in vitro by neurotrophins. Expression patterns of splice variants in vivo and neurotrophin-induced regulation without changes in cell composition in vitro demonstrate that neurexin splice variant expression varies during differentiation of individual neurons. Our data suggest that changes in neurexin splice variants contribute to alterations of neuronal cell surface properties during target innervation.