Fig. 1

Generation of the ∆Ig3-MuSK mouse. A Schematic representation of full length and ∆Ig3-MuSK isoforms. The extracellular full-length isoform contains three immunoglobulin (Ig)-like domains (Ig1, Ig2, and Ig3) as well as a CRD/Fz and an intracellular tyrosine kinase domain. ∆Ig3-MuSK lacks the BMP-binding Ig3 domain. B CRISPR-Cas9 was used to delete exon 6 and 7, which encode the Ig3 domain, along with the intervening intronic sequence to generate the ∆Ig3-MuSK allele. C PCR amplification of WT and ∆Ig3-MuSK alleles in WT and ∆Ig3-MuSK heterozygous and homozygous mice using allele-specific primers (depicted in B). The animal weights (D) and grip strength (E) of 3-month-old WT and ∆Ig3-MuSK were comparable. Innervation of Ig3-MuSK NMJs, as assessed by overlap of pre- and postsynaptic structures normalized to WT overlap, was equivalent to that in WT in both the fast EDL (F) and slow soleus (G) (EDL: n = 3 animals per genotype, SOL: n = 6 animals per genotype, t-test n.s. in both muscles)