Table 1.

Quantification of agrin-induced clustering of CD4-subunit loops and β loop fragments

CD4-chimeraNo. of experimentsNo. of myotubes counted% myotubes with clusters
CD45801
CD4−
    α loop5880
    β loop69473
    γ loop3570
    δ loop5633
    ε loop5750
    β333–406611774
    β407–4695842
    β333–406/ε611177
    β370–40636045
    β loop Y390F61001
    β333–406 Y390F3572
    β333–406/ε Y390F3530
    β370–406 Y390F3603
CD4ct−
    β382–40136088
    β382–401 Y390F36015
    β385–3963605
    δ385–40436022
  • CD4-chimera-positive myotubes were identified in random fields and scored for the presence or absence of CD4 clusters that colocalized with AChR clusters. Agrin induced robust clustering of CD4-β loop chimeras encompassing amino acids 382–401, with 45–88% of the expressing myotubes having clusters. Mutation of Y390 abolished clustering of these constructs, and all other CD4-loops showed background or weak colocalization with AChR clusters.