Differential seizure-induced and developmental changes of neurexin expression

The neurexins are differentially expressed neuronal surface proteins. Each neurexin gene (I, II, and III) has two promoters giving alpha and beta major isoforms, and alternative splicing generates further extensive diversity. Following kainate- and pentylenetetrazole-induced seizures, there were no specific changes of expression of neurexins I and III in rat brains, whereas neurexin II expression increased in the dentate gyrus of the hippocampus. Both major isoforms were induced, particularly neurexin II alpha. No significant alteration of neurexin II RNA splicing was observed. During postnatal development, neurexin II expression peaked in 6- to IO-day-old animals, in contrast with that of neurexins I and III; while neurexin II alpha expression was elevated, neurexin II beta expression was constant. The data suggest differential functions of the three neurexins and of their alpha- and beta-isoforms and implicate neurexin II alpha in the establishment of functional neuronal circuitry in postnatal brain and activity-dependent changes in adult brain.