Glycine receptors in the developing rat spinal cord

Abstract

Inhibitory glycine receptors (GlyRs) undergo developmental regulation with α2 subunits most abundant at prenatal and early postnatal stages, and α1 subunits predominating in adults. In comparing the relative amounts of mRNA for two known splice variants of the α2 subunit, α2A and α2b, in the rat spinal cord at different stages of development, I found evidence for the existence of an additional, novel variant. This variant, missing exon 3, I have termed "α2N." Examination of the RNA from spinal cords of different-aged rats indicated that α2N undergoes dramatic down-regulation during prenatal development. Its mRNA forms a significant portion of the α2 subunit pool at E14, but is nearly undetectable at the time of birth. I also examined the developmental changes in two factors that can regulate GlyR α2 pre-mRNA splicing, the splicing factor neurooncological ventral antigen-1 (Nova-1) and the brain isoform of the polypyrimidine tract binding protein (brPTB). Treatment of neurons in culture with antisense oligonucleotides to "knock down" one of the Nova-1 variants altered the expression of GlyR α2N. These results suggest that the relative levels of the variants of Nova-1 and brPTB may play a role in the developmental regulation of GlyR α2N. Based on these results I propose a model for the developmental regulation of GlyR α2N. These results provide evidence for a novel splice variant of the GlyR α2 subunit that undergoes dramatic developmental regulation, and reveal the developmental profiles of two possible regulators of its expression during development.