Characterization of Meteorin--an evolutionary conserved neurotrophic factor.

Growth factors control cellular growth, proliferation, and differentiation and may have therapeutic applications. In this study, we focus on Meteorin which is a member of a largely uncharacterized evolutionary conserved two-member growth factor family. Our analysis shows that Meteorin is expressed in the central nervous system both during development and in adult mice. Detailed immunohistological analysis of the adult mouse brain reveals that Meteorin is highly expressed in Bergmann glia and in a few discrete neuronal populations residing in the superior colliculus, the ocular motor nucleus, the raphe and pontine nuclei, and in various thalamic nuclei. In addition, low levels of Meteorin is found in astrocytes (S100beta+, OX42-) distributed ubiquitously throughout the brain. Meteorin was cloned and recombinant protein purified allowing N-terminal sequencing and mass spectrometric analysis showing that Meteorin is secreted as an unmodified monomer. This form is bioactive as it induces neurite outgrowth from dorsal root ganglions in vitro. Intrastriatal protein injection and lentiviral studies in vivo showed that Meteorin is a highly diffusible molecule in the brain and cellular uptake is apparent in specific populations which may carry the receptor. In summary, we provide a comprehensive expression analysis and have made and thoroughly validated molecular tools to help investigate the therapeutic potential of Meteorin.