Extracellular matrix glycoproteins inhibit neurite outgrowth of different types of identified leech neurons in culture.
We explored the contribution of inhibitory peanut-binding extracellular matrix glycoproteins to the regeneration of characteristic outgrowth patterns by different types of identified neurons. Adult leech neurons were isolated one by one and plated in culture on a substrate that consisted of the capsules that encase the CNS ganglia. On the inside surface of this substrate, a combination of growth-promoting and -inhibiting extracellular matrix glycoproteins regulates the regeneration of distinctive outgrowth patterns by different neuron types. The role of inhibitory glycoproteins that bind to peanut lectin was studied by perturbation experiments in which peanut lectin was added to the culture medium. The effects of peanut lectin on the outgrowth patterns depended on the specific cell type that was tested. Anterior pagoda neurons, which on capsules produce a bipolar outgrowth pattern, in the presence of the lectin multiplied the number of primary neurites and the total neurite length and also lost their bipolarity. Annulus erector motoneurons, which on capsules grow poorly, in the presence of peanut lectin sprouted 70% more neurites and duplicated their total neurite length. By contrast, Retzius neurons which grow profusely on ganglion capsules, in the presence of peanut lectin increased the number of primary neurites without increasing their total neurite length or branch points. When neurons were plated on plastic, peanut lectin added to the culture medium did not affect the growth of neurons, thus showing that the effects of peanut lectin were induced by blocking the binding of neurons to inhibitory glycoproteins on the capsules. These results show that regeneration of different neuron types has different regulation by inhibitory extracellular matrix molecules.