OVEREXPRESSION OF NERVE GROWTH-FACTOR IN EPIDERMIS OF TRANSGENIC MICEPRESERVES EXCESS SENSORY NEURONS BUT DOES NOT ALTER THE SOMATOTOPIC ORGANIZATION OF CUTANEOUS NERVE PROJECTIONS

determine how target-derived nerve growth factor (NGF) affects sensory neuronal survival and the development of topographic nerve projection s in the spinal cord, anatomical studies were performed on transgenic mice that overexpress NGF in skin and other keratinized epithelial str uctures. Transgenic animals showed a 100% increase in the number of se nsory neurons in specific dorsal root ganglia and exhibited significan tly more fibers immunoreactive for calcitonin gene-related peptide in the dorsal horn compared to control animals. This confirms earlier stu dies which suggested that naturally occurring sensory neuronal death i s decreased, or eliminated, in the transgenic mice. Nerve labeling stu dies showed that the somatotopic organization of cutaneous nerve proje ctions was not altered in the transgenic animals. These data suggest t hat neuronal death does not act to remove sensory neurons that project to inappropriate regions of the spinal cord.