Involvment of the neuromuscular junction Schwann cells in the motor endplate disease

Terminal Schwann cells are non-myelinating cells, which wrap around the nerve terminal at the neuromuscular junction (NMJ). In med (motor endplate disease) mice, neuromuscular transmission is severely impaired and death occurs 20 days after birth. This phenotype is due to a mutation in the SCn8a gene coding for the Nav1.6 voltage-gated sodium channel. We examined the NMJ components in med mice by immunofluorescence and confocal microscopy on whole mounts of sternal triangularis muscles. Strikingly, in mutant mice, the non-myelinated pre-terminal region of axons showed abundant sprouting and most of the endplates were devoid of Terminal Schwann cells. Our data supports the hypothesis that the lack of expression of Nav 1.6 in Schwann cell might participate in the med phenotype.