title: Differential requirement for MuSK and dystroglycan in generating patterns of neuromuscular innervation.
abstract: Vertebrates display diverse patterns of neuromuscular innervation, but little is known about how such diversity is generated. In mammals, neuromuscular junctions form predominantly at equatorial locations, giving rise to a focal innervation pattern along a central endplate band. In addition, vertebrate striated muscles exhibit two nonfocal neuromuscular patterns, myoseptal and distributed innervation. Although agrin-MuSK-rapsyn signaling is essential for the focal innervation pattern, it is unknown whether the same genetic program also controls synaptogenesis at nonfocal innervation sites. Here we show that one of three transcripts generated by the zebrafish unplugged locus, unplugged FL, encodes the zebrafish MuSK ortholog. We demonstrate that UnpFL/MuSK is critical for the assembly of focal synapses in zebrafish and that it cooperates with dystroglycan in the formation of nonfocal myoseptal and distributed synapses. Our results provide the first genetic evidence that neuromuscular synapse formation can occur in the absence of MuSK and that the combinatorial function of UnpFL/MuSK and dystroglycan generates diverse patterns of vertebrate neuromuscular innervation.
authors.affiliation: Department of Cell, University of Pennsylvania School of Medicine, Philadelphia, PA 19104-6058, USA.
authors.forename: Julie L
authors.initials: JL
authors.lastname: Lefebvre
authors.forename: Lili
authors.initials: L
authors.lastname: Jing
authors.forename: Sara
authors.initials: S
authors.lastname: Becaficco
authors.forename: Clara
authors.initials: C
authors.lastname: Franzini-Armstrong
authors.forename: Michael
authors.initials: M
authors.lastname: Granato
mesh_terms: D000818:Animals; D049030:Dystroglycans / Q000502:physiology*; D018398:Homeodomain Proteins; D009132:Muscles / Q000294:innervation*; D009469:Neuromuscular Junction; D012333:RNA, Messenger; D020794:Receptor Protein-Tyrosine Kinases / Q000235:genetics / Q000502:physiology*; D015398:Signal Transduction; D013569:Synapses; D015027:Zebrafish; D029961:Zebrafish Proteins / Q000235:genetics / Q000502:physiology*
chemical_list: D018398:Homeodomain Proteins; C490829:MuSK protein, zebrafish; D012333:RNA, Messenger; D029961:Zebrafish Proteins; D049030:Dystroglycans; D020794:Receptor Protein-Tyrosine Kinases