Tenascin and laminin function in target recognition and central synaptic differentiation

The influence of the target cell-issued extracellular molecules tenascin-C and laminin on synaptogenesis was studied in mixed primary cultures of pitu itary melanotrophs and hypothalamic neurons. We could demonstrate in this n euron-target coculture system a new role for tenascin-C, which appeared to be expressed as an early and transitory signal of target recognition for se lective afferent fibers. Tenascin-C expression disappeared from the melanot rophs soon after the establishment of neural contacts. Concomitantly, the m elanotrophs became immunoreactive for laminins, and more specifically for t he synaptic isoform beta (2) chain-containing laminin. The laminin signal a ppeared to be involved in the induction of synaptic differentiation, select ively with fibers containing both dopamine and GABA, like those innervating the melanotrophs in situ. NeuroReport 12:1073-1076 (C) 2001 Lippincott Wil liams & Wilkins.