TY - JOUR
T1 - Nerve-independent formation of a topologically complex postsynaptic apparatus
AU - Kummer, Terrance T.
AU - Misgeld, Thomas
AU - Lichtman, Jeff W.
AU - Sanes, Joshua R.
PY - 2004/3/29
Y1 - 2004/3/29
N2 - As the mammalian neuromuscular junction matures, its acetylcholine receptor (AChR)-rich postsynaptic apparatus is transformed from an oval plaque into a pretzel-shaped array of branches that precisely mirrors the branching pattern of the motor nerve terminal. Although the nerve has been believed to direct postsynaptic maturation, we report here that myotubes cultured aneurally on matrix-coated substrates form elaborately branched AChR-rich domains remarkably similar to those seen in vivo. These domains share several characteristics with the mature postsynaptic apparatus, including colocalization of multiple postsynaptic markers, clustering of subjacent myonuclei, and dependence on the muscle-specific kinase and rapsyn for their formation. Time-lapse imaging showed that branched structures arise from plaques by formation and fusion of AChR-poor perforations through a series of steps mirroring that seen in vivo. Multiple fluorophore imaging showed that growth occurs by circumferential, asymmetric addition of AChRs. Analysis in vivo revealed similar patterns of AChR addition during normal development. These results reveal the sequence of steps by which a topologically complex domain forms on a cell and suggest an unexpected nerve-independent role for the postsynaptic cell in generating this topological complexity.
AB - As the mammalian neuromuscular junction matures, its acetylcholine receptor (AChR)-rich postsynaptic apparatus is transformed from an oval plaque into a pretzel-shaped array of branches that precisely mirrors the branching pattern of the motor nerve terminal. Although the nerve has been believed to direct postsynaptic maturation, we report here that myotubes cultured aneurally on matrix-coated substrates form elaborately branched AChR-rich domains remarkably similar to those seen in vivo. These domains share several characteristics with the mature postsynaptic apparatus, including colocalization of multiple postsynaptic markers, clustering of subjacent myonuclei, and dependence on the muscle-specific kinase and rapsyn for their formation. Time-lapse imaging showed that branched structures arise from plaques by formation and fusion of AChR-poor perforations through a series of steps mirroring that seen in vivo. Multiple fluorophore imaging showed that growth occurs by circumferential, asymmetric addition of AChRs. Analysis in vivo revealed similar patterns of AChR addition during normal development. These results reveal the sequence of steps by which a topologically complex domain forms on a cell and suggest an unexpected nerve-independent role for the postsynaptic cell in generating this topological complexity.
KW - Acetylcholine receptor
KW - Laminin
KW - Muscle
KW - Neuromuscular junction
KW - Synapse formation
UR - http://www.scopus.com/inward/record.url?scp=1842613541&partnerID=8YFLogxK
U2 - 10.1083/jcb.200401115
DO - 10.1083/jcb.200401115
M3 - Article
C2 - 15037598
AN - SCOPUS:1842613541
SN - 0021-9525
VL - 164
SP - 1077
EP - 1087
JO - Journal of Cell Biology
JF - Journal of Cell Biology
IS - 7
ER -