Extensive multiple innervation and abnormal synaptogenesis in muscular dysgenesis (mdg/mdg) in the mouse embryo.
Muscular dysgenesis (mdg) is an autosomal recessive mutation in the mouse characterized by total muscle inactivity in vivo or in vitro. The muscle fiber in the mdg/mdg diaphragm was not only morphologically abnormal but also multiply innervated; the motor innervation was very dense, showing overgrowth and sprouting. As expected at the ultrastructural level, nerve-muscle contacts were composed of dense appositions of numerous axon terminals (dense focal polyinnervation). Moreover, these mdg/mdg neuromuscular junctions, lacking post-synaptic unfolding, were immature compared to the control ones. This retarded neuromuscular junction differentiation in muscular dysgenesis may be related to considerable delay in muscle maturation and/or abnormal muscular differentiation, or to a nerve defect independent of, or causally related to, the muscular defect.
D000818:Animals; D003964:Diaphragm / Q000294:innervation*; D051379:Mice; D008854:Microscopy, Electron; D009046:Motor Neurons / Q000648:ultrastructure*; D009135:Muscular Diseases / Q000196:embryology / Q000473:pathology / Q000662:veterinary*; D009469:Neuromuscular Junction / Q000648:ultrastructure*; D010791:Phrenic Nerve / Q000648:ultrastructure; D012376:Rodent Diseases / Q000196:embryology* / Q000473:pathology; D013569:Synapses / Q000648:ultrastructure