IDENTIFICATION OF GENES DIFFERENTIALLY EXPRESSED BY NERVE GROWTH FACTOR-DEPENDENT AND NEUROTROPHIN-3-DEPENDENT SENSORY NEURONS

The neurotrophins nerve growth factor (NGF) and neurotrophin-3 (NT3) s upport the survival of subpopulations of primary sensory neurons with defined and distinct physiological characteristics. Only a few genes h ave been identified as being differentially expressed in these subpopu lations, and not much is known about the nature of the molecules invol ved in the processing of sensory information in NGF-dependent nocicept ive neurons or NT3-dependent proprioceptive neurons, We devised a simp le dorsal root ganglion (DRG) explant culture system, allowing the sel ection of neuronal populations preferentially responsive to NGF or NT3 , The reliability of this assay was first monitored by the differentia l expression of the NGF and NT3 receptors trkA and trkC, as well as th at of neuropeptides and calcium binding proteins, We then identified f our differentially expressed sodium channels, two enriched in the NGF population and two others in the NT3 population, Finally, using an opt imized RNA fingerprinting protocol, we identified 20 additional genes, all differentially expressed in DRG explants cultured with NGF or NT3 , This approach thus allows the identification of large number of gene s expressed in subpopulations of primary sensory neurons and opens the possibility of studying the molecular mechanisms of nociception and p roprioception.