NT-4 is part of the family of neurotrophic factors,neurotrophins,that are in charge for the survival and differentiation of mammalian neurons. NT-4 expression is dominant and less influenced by environmental signals. NT-4 deficient mice shows slight cellular deficits and develop normally to adulthood. NT-4 is a target-derived survival factor for peripheral sensory sympathetic neurons.NT-4 is involved in the proliferation and differentiation of periodontal ligament cells.