Neurons induce contractions in myotubes containing only muscular dysgenic nuclei

Muscular dysgenic (mdg/mdg) myotubes cultured alone do not contract. Glucosephosphate isomerase (GPI-1) isozymes were analyzed to determine the final genotype of cultured dysgenic (mdg/mdg, gpi-1a/a) myotubes to which normal embryonic spinal cord and limb cells (CBA/J +/+, gpi-1b/b) had been added. Although both myoblast and spinal cord cell additions caused induction of spontaneous contractions, only myoblasts fused with the myotubes to create functional heterokaryons. Spinal cord cells did not fuse with dysgenic myotubes, but formed functional synapses.