Neuropoietin (NP, also known as cardiotrophin-2) is a 19.7 kDa member of the IL-6 family of cytokines. Considered to be the product of a gene duplication event involving cardiotrophin-1 (CT-1), it helps to define a subfamily within the IL-6 family that includes CT-1, CLC and CTNF. Mouse neuropoietin is synthesized as a 204 amino acid (aa) precursor that contains a 22 aa signal sequence and a 192 aa mature segment. Mature mouse neuropoietin shares 88%, 90% and 95% aa identity to chimpanzee, canine and rat neuropoietin, respectively. NP will mediate motor neuron survival, and appears to be selectively expressed in the embryo by tissues involved with nervous system development.