RESUMO
Signals regulating diversification of olfactory sensory neurons to express odorant receptors and other genes necessary for correct assembly of the olfactory sensory map persist in the olfactory epithelium of adult mouse. We have screened for genes with an expression pattern correlating with the topography odorant receptor-expression zones. The Msx1 homeobox gene and a semaphorin receptor (Neuropilin-2) showed graded expression patterns in the olfactory epithelium. The gradients of Msx1 and Neuropilin-2 expression in basal cells and neurons, respectively, correlated with expression of a retinoic acid-synthesizing enzyme (RALDH2) in lamina propria. A BMP-type I receptor (Alk6) showed a reverse gradient of expression in the supporting cells of the epithelium. Considering known functions of identified genes in cell specification and axon guidance this suggests that zonal division of the olfactory sensory map is maintained, during continuous neurogenesis, as a consequence of topographic counter gradients of positional information.
Assuntos
Expressão Gênica/fisiologia , Cavidade Nasal/inervação , Cavidade Nasal/metabolismo , Neurônios Receptores Olfatórios/metabolismo , Proteínas Serina-Treonina Quinases , Receptores de Fatores de Crescimento , Fatores de Transcrição , Receptores de Ativinas Tipo I/biossíntese , Receptores de Ativinas Tipo I/genética , Aldeído Oxirredutases/biossíntese , Aldeído Oxirredutases/genética , Animais , Receptores de Proteínas Morfogenéticas Ósseas Tipo I , Proteínas de Homeodomínio/biossíntese , Proteínas de Homeodomínio/genética , Fator de Transcrição MSX1 , Camundongos , Camundongos Endogâmicos C57BL , Cavidade Nasal/citologia , Proteínas do Tecido Nervoso/biossíntese , Proteínas do Tecido Nervoso/genética , Proteínas do Tecido Nervoso/metabolismo , Neuropilina-1 , Mucosa Olfatória/metabolismo , Retinal DesidrogenaseRESUMO
The intracellular signal transduction machinery of heterotrimeric G-protein coupled odorant and putative pheromone receptors converts odorous information into a cellular response. We have investigated for the presence of 18 members of the family termed "regulators of G-protein signaling" (RGS) in primary olfactory sensory neurons of the main as well as the accessory (vomeronasal) system of the mouse. Unexpectedly, expression of a few RGS members show spatial restrictions correlating with the patterns described for G-protein coupled receptors in these two types of olfactory neurons. RGS3 was selectively coexpressed with the Galphai2 G-protein subunit in a subpopulation of vomeronasal neurons. The mutually exclusive spatial extents of RGS9 and RGSZ1 expression in main olfactory neurons corresponded precisely to that of certain odorant receptor zones. This renders these RGS members the first described intracellular signal transduction components with a potential role in the spatially organized sensory coding in the main olfactory system.
