The increased expression of the synaptic vesicle marker synaptophysin induced by GDNF might have fundamental impact on understanding the pathogenesis of DD as well as of other enteric neuropathies: Recent research work in several neurodegenerative disorders of the CNS has emphasized the importance of synaptic dysfunction as the initial event preceeding subsequent neurodegeneration [43]. The gene discussed is SYP; the disease is dentin dysplasia.