| The peripheral axons of trigeminal sensory neurons innervate the skin of the head and are responsible for the sensation of touch, temperature, and pain. To investigate zebrafish sensory axon development and regeneration I have employed a variety of techniques including electron microscopy, molecular genetics, two-photon axotomy, and time-lapse confocal imaging. I found that sensory axons arborize between skin cells and are sealed tightly between and within skin cells once arborization has ceased. The capacity for axon regeneration and plasticity is significantly diminished after axon arbors are stabilized. Regenerating axons are repelled by their former territory and uninjured axons do not sprout into denervated skin. Attenuation of the Nogo Receptor pathway significantly improved skin reinnervation by regenerating axons. The mature zebrafish skin is thus a nonpermissive environment for axon growth. In addition, I found that epidermal cells may be the cell type responsible for clearance of degenerating peripheral sensory axons. |
