Possible roles for cell-to-substratum adhesion in neuronal morphogenesis

The role of cell-to-substratum adhesion in the initiation, elongation, and branching of axons from embryonic sensory neurons was investigated. Cells from sensory ganglia of 4–8-day-old chicken embryos were cultured on several substrata: including collagen; polyornithine-, polylysine-, and polyglutamate-coated surfaces, and tissue culture dishes. The air-blaster method was used to measure growth cone-substratum adhesion. Growth cones adhere much more strongly to polyornithine- or polylysine-coated surfaces and to the upper surfaces of glial cells than to tissue culture plastic. Axons, too, adhere tightly to these substrata, and are crooked, whereas on tissue culture plastic, axons are not adherent and are straight. The fraction of neurons that form axons and the rates of axonal elongation and branching are markedly increased when cells are cultured on polyornithine-coated dishes as compared to tissue culture dishes. This correlation of strong adhesion and enhanced neuronal morphogenesis suggests that adhesive interactions between the growth cone and the microenvironment in an embryo are crucial parts of the initiation and elongation of neuronal processes. Regulation of neuronal morphogenesis may be expressed through the physicochemical properties of the interacting cell surfaces and extracellular environment.