CONTACT GUIDANCE OF CNS NEURITES ON GROOVED QUARTZ - INFLUENCE OF GROOVE DIMENSIONS, NEURONAL AGE AND CELL-TYPE

We used an in vitro system that eliminates competing guidance cues fou nd in embryos to determine whether substratum topography alone provide s important neurite guidance information, Dissociated embryonic Xenopu s spinal cord neurons and rat hippocampal neurons were grown on quartz etched with a series of parallel grooves. Xenopus neurites grew paral lel to grooves as shallow as 14 nm and as narrow as 1 mu m, Hippocampa l neurites grew parallel to deep, wide grooves but perpendicular to sh allow, narrow ones, Grooved substrata determined the sites at which ne urites emerged from somas: Xenopus neurites sprouted from regions para llel to grooves but presumptive axons on rat hippocampal neurons emerg ed perpendicular to grooves and presumptive dendrites emerged parallel to them, Neurites grew faster in the favored direction of orientation and turned through large angles to align on grooves, The frequency of perpendicular alignment of hippocampal neurites depended on the age o f the embryos from which neurons were isolated, suggesting that contac t guidance is regulated in development, Collectively, the data indicat e that substratum topography is a potent morphogenetic factor for deve loping CNS neurons and suggest that in addition to a role in pathfindi ng the geometry of the embryo assists in establishing neuronal polarit y, In the companion paper (A. M. Rajnicek and C. D. McCaig (1997) J. C ell Sci. 110, 2915-2924) we explore the cellular mechanism for contact guidance of growth cones.