of neuronal ganglion cells from the intestinal tract. Previous studies indicate a role of NRTN gene mutations in the disease. One study showed evidence that a mutation in the NRTN gene was not enough alone to cause onset of the disease, however when coupled with a mutation in the RET gene, disease was present in family members as well as the individual. A more recent study showed NRTN variants present in individuals with Hirschsprung disease. However, RET associated mutations were not found and in one variant, RET phosphorylation levels were reduced, which has the potential to have downstream effects on the proliferation and differentiation of neuronal crests. Also, high levels of expression of neurturin were found to be associated with nephroblastoma indicating the possible that the growth factor could be influencing differentiation. Lastly, a study also associated neurturin deficiency in mice with keratoconjunctivitis and dry eye. Therapeutic potential Evidence showing neurturin’s role in neuron survival and management has made it a popular candidate for the potential treatment or reversal of neurodegeneration. In addition, mice models have shown the dying neurons exposed to trophic factors can be rescued. Neurturin is an example of a trophic factor that is difficult to utilize clinically because of its inability to cross the blood-brain barrier of the CNS (central nervous system). Ceregene sponsored a double-blind phase II clinical trial of CERE-120, a viral vector mediated gene transfer drug that allows for the continuous delivery of neurturin to the nigrostratial system. The hope was to reverse damaged and diseased tissue in Parkinson's patients and overall slow the progression of the disease. However, results were inconclusive and showed that while the drug appears to be relatively safe, there was no statistically significant data supporting the improvement of motor function or neuronal health. Neurturin’s therapeutic potential is unknown and future studies aim to improve delivery of the drug. References External links Biomolecules TGFβ domain Neurotrophic factors