M. Iglesias et al., S-LAMININ AND N-ACETYLGALACTOSAMINE LOCATED AT THE SYNAPTIC BASAL LAMINA OF SKELETAL-MUSCLE ARE INVOLVED IN SYNAPTIC RECOGNITION BY GROWINGNEURITES, Journal of neurocytology, 24(12), 1995, pp. 903-915
The purpose of the work reported here is to identify molecular compone
nts of the synaptic basal lamina of skeletal muscle fibres which allow
recognition of original synaptic sites by regenerating motor axons. W
e focused on s-laminin and components recognized by the lectin Dolicho
s biflorus agglutinin previously shown to be specifically located at t
he synaptic basal lamina. We used a cryoculture bioassay in which chic
k ciliary ganglion neurons grow on rat skeletal muscle cryostat sectio
ns. In control cultures, neurites extended over the muscle sections in
close association with the muscle cell surface. It was observed that
most of the neurites that extended towards the endplate zone and reach
ed an area of 40 mu m around the neuromuscular junction ceased to grow
when they contacted the synaptic site. Masking either lectin receptor
s or some s-laminin molecule epitopes prior to the culture of neurons
alters the behaviour of growing neurites. On sections treated either w
ith Dolichos biflorus agglutinin or anti s-laminin monoclonal antibodi
es (D5 and C4) most of the neurites did not stop their growth at the s
ynaptic regions. Moreover, treating muscle sections with Dolichos bifl
orus agglutinin removed the gradient of substratum affinity around the
endplate. These results indicate that the s-laminin and Dolichos bifl
orus agglutinin receptors present on muscle cell surfaces may play a f
unctional role in the interaction of growing neurites with original sy
naptic sites in the process of neuromuscular regeneration.