Molecular analysis of developmental plasticity in neocortex

Gene expression studies indicate that during activity-dependent development al plasticity, N-methyl-D-aspartate receptor activation causes a Ca2+-depen dent increase in expression of transcription factors and their downstream t argets. The products of these plasticity genes then operate collectively to bring about the structural and functional changes that underlie ocular dom inance plasticity in visual cortex. Identifying and characterizing plastici ty genes provides a tool for molecular dissection of the mechanisms involve d. Members of second-messenger pathways identified in adult plasticity para digms and elements of the transmission machinery are the first candidate pl asticity genes tested for their role in activity-dependent developmental pl asticity. Knockout mice with deletions of such genes have allowed analyzing their function in the context of different systems and in different paradi gms. Studies of mutant mice reveal that activity-dependent plasticity is no t necessarily a unified phenomenon. The relative importance of a gene can v ary with the context of its expression during different forms of plasticity . Forward genetic screens provide additional new candidates for testing, so me with well-defined cellular functions that provide insight into possible plasticity mechanisms. (C) 1999 John Wiley & Sons, Inc.