Changes in mRNA of Slit-Robo GTPase-activating protein 2 following facial nerve transection.

Complex processes following peripheral nerve injury integrate a number of various external cues and their intracellular responses resulting in the cytoskeletal remodeling. One of these cues, Slit protein, plays an important role in neuronal migration and axonal guidance through the interaction with Roundabout (Robo) receptor. It was reported that the signal from Robo is transmitted to a specific family of GTPase-activating proteins (GAPs) named Slit-Robo GAPs. The Slit-Robo GAPs (srGAPs) further transmit the signal to the actin cytoskeleton controlling Rho GTPases and thus provide a direct link between Slit-Robo signaling and actin cytoskeleton. We examined the effects of facial nerve transection on srGAP2 mRNA expression in the facial nerve nuclei by in situ hybridization. SrGAP2 mRNA was initially expressed, and its expression increased from 3 to 28 days after transection, with the peak at the seventh day after axotomy. The upregulation was found mostly in the neuronal cells and only to a small extent in the glial cells. Our results suggest that srGAP2, as a part of Slit-Robo pathway, plays an important role in the axonal regeneration after axotomy.