Regulated expression of the proteoglycan SPOCK in the neuromuscular system

SPOCK is prevalent in developing synaptic fields of the central nervous sys tem (Charbonnier et al., 2000. Mech. Dev. 90, 317-321). The expression of S POCK during neuromuscular junction (NMJ) formation was compared to agrin an d acetylcholine receptor (AChR) distribution. SPOCK is detected within the myogenic masses during the early steps of embryonic development, and distri buted in the cytoplasm of myotubes before coclustering with AChRs. In the a dult, SPOCK is present in axons and is highly expressed by Schwann cells. S POCK altered expression pattern after nerve lesioning, or cholinergic trans mission blockade, strongly indicate that its cellular distribution at the N MJ depends on innervation. (C) 2000 Elsevier Science Ireland Ltd. All right s reserved.