DOES CILIARY NEUROTROPHIC FACTOR SERVE A DIFFERENT FUNCTION IN THE RAT VERSUS THE CHICKEN

Ciliary neurotrophic factor (CNTF) was first identified as a trophic a ctivity that was able to support the survival of chick ciliary ganglio n (CG) neurons in vitro. CNTF from rabbit and rat were subsequently pu rified from sciatic nerve and their cDNA sequences cloned. Another tro phic molecule for CG neurons was identified as a growth promoting acti vity (GPA). GPA was purified from chicken sciatic nerve and cloned fro m embryonic chicken eye. The rat and rabbit CNTFs have a considerable amount of structural homology and are not secreted in significant quan tities, whereas GPA is less similar in that it is only 49% homologous with rabbit and rat CNTF and is secreted by cells. This review discuss es other similarities and differences in biological activities, molecu lar structure, receptor signaling and cellular distribution between CN TF and GPA and suggests that these molecules may have different functi ons in rodents and birds.