The olfactory bulb (OB) represents an excellent model to study neural plasticity due to persistent neurogenesis in adult life and the possibility to study activity-regulated phenomena by peripheral denervation. NMDA receptors are postsynaptically expressed on mitral cell dendrites receiving excitatory afferents from peripheral olfactory neurons, and on granule cells making dendro-dendritic contacts with mitral cells. The NMDA receptor is assembled as a tetramer containing NR1 and NR2, and possibly NR3 subunits. The NR1 gene encodes for mRNAs that generate at least eight functional variants by alternative splicing of exon 5 (cassette N1), 21 (cassette C1), or 22 (cassettes C2 or C2'). In the present work we tested the possibility that sensory inputs regulates NMDA receptor subunit expression and alternative splicing. To this aim we analyzed the expression levels of NR1 and NR2A-D subunits 2, 8, 14, 21, 44, 65 and 100 days after OB peripheral denervation by zinc sulfate nasal irrigation. Taking advantage of the laminar organization of the OB, we microdissected each layer and processed it for quantitative RT-PCR and western blot analysis respectively. The NR2 subunits generally showed minor changes with the exception of NR2D, whose expression was significantly downregulated starting from 8 days post lesion (dpl) in the glomerular layer. In the mitral cell layer we found that N1-lacking NR1 subunits were transiently upregulated early after deafferentation to go back to normal levels by 21 dpl. In contrast, N1-containing subunits durably decreased their expression starting from 8 dpl up to100 dpl. The ratio between N1 lacking/N1-containing transcripts changed from 1.2 (control) to 2.3 (14 dpl) to 1.9 (100 dpl). Similar changes were observed in the granule cell layer. These results imply that in the OB sensory activity is able to regulate the N1 cassette splicing of NR1 subunits.
Sensory input regulates splicing of the N1 cassette in NMDAR1 subunits of the adult olfactory bulb
BOVETTI, Serena;BOVOLIN, Patrizia;FASOLO, Aldo
2004-01-01
Abstract
The olfactory bulb (OB) represents an excellent model to study neural plasticity due to persistent neurogenesis in adult life and the possibility to study activity-regulated phenomena by peripheral denervation. NMDA receptors are postsynaptically expressed on mitral cell dendrites receiving excitatory afferents from peripheral olfactory neurons, and on granule cells making dendro-dendritic contacts with mitral cells. The NMDA receptor is assembled as a tetramer containing NR1 and NR2, and possibly NR3 subunits. The NR1 gene encodes for mRNAs that generate at least eight functional variants by alternative splicing of exon 5 (cassette N1), 21 (cassette C1), or 22 (cassettes C2 or C2'). In the present work we tested the possibility that sensory inputs regulates NMDA receptor subunit expression and alternative splicing. To this aim we analyzed the expression levels of NR1 and NR2A-D subunits 2, 8, 14, 21, 44, 65 and 100 days after OB peripheral denervation by zinc sulfate nasal irrigation. Taking advantage of the laminar organization of the OB, we microdissected each layer and processed it for quantitative RT-PCR and western blot analysis respectively. The NR2 subunits generally showed minor changes with the exception of NR2D, whose expression was significantly downregulated starting from 8 days post lesion (dpl) in the glomerular layer. In the mitral cell layer we found that N1-lacking NR1 subunits were transiently upregulated early after deafferentation to go back to normal levels by 21 dpl. In contrast, N1-containing subunits durably decreased their expression starting from 8 dpl up to100 dpl. The ratio between N1 lacking/N1-containing transcripts changed from 1.2 (control) to 2.3 (14 dpl) to 1.9 (100 dpl). Similar changes were observed in the granule cell layer. These results imply that in the OB sensory activity is able to regulate the N1 cassette splicing of NR1 subunits.
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