GROWTH-FACTOR REGULATION OF NEURONAL DEVELOPMENT

Recent experimental investigations have redefined the spectrum of grow th factors and developmental signalling pathways that are necessary to orchestrate the growth and differentiation of regional neuronal subpo pulations. Gene knockout studies of the classic neurotrophins and thei r high-affinity tyrosine kinase (Trk) receptors have refined our defin ition of the cellular mechanisms and target populations of these neuro notrophic factors. Recognition of the significant parallels that exist between neuropoiesis and hematolymphopoiesis has fostered our study o f the range and cellular actions of these hemopoietins in neuronal dev elopment. In addition, by activating receptor subunits that possess se rine/threonine activity, bone morphogenetic proteins of the transformi ng growth factor-beta superfamily exhibit complex spatiotemporal regul ation of regional neuronal subpopulations. These collective observatio ns suggest that a complex hierarchy of epigenetic signals is required for the growth and maturation of regional neuronal lineage species in the central and peripheral mammalian nervous system.