Fig. 3

aN-glycan analysis of muscle fibronectin (Fn) isolated from control and LGMD2I and CMD patient cells. Blue box highlights the area of change at m/z 965.9 and m/z1111.4. b Quantification n = 3 averaged from three experimental replicates, each repeated with three technical replicates (*P < 0.05). c Co-immunoprecipitation of collagen released from purified fibronectin, normalised to healthy human controls (***P < 0.0001); three technical repeats repeated three times, box represents 5–95%, median centre line, whiskers = SEM. d Collagen and fibronectin binding quantitated via Biacore, before and after treatment with neuraminidase, an enzyme that specifically removes terminal sialic acid residues. e Schematic of the fibronectin rescue experiment. f Injection of human fibronectin into the single-cell stage of 1-dpf embryos. Fibronectin tagged with Alexa488 localises correctly to the myosepta in wild-type larvae, white arrows. Scale bar = 100 μm. Only fully sialylated fibronectin can rescue collagen deficits evident in fkrp^−/− larvae. fkrp^+/+ and fkrp^−/− larvae uninjected or injected, with either desialylated fibronectin or fully sialylated fibronectin, visualised for collagen localisation via z projections of the entire mediolateral extent of the myotome centred on the anal pore. Note also that fkrp^+/+ control fish, injected with sialylated fibronectin, exhibited a lower collagen deposition at the myoseptal boundaries. This lower collagen deposition is attributed to a previously described fibronectin–collagen feedback loop, scale bar = 100 μm. g Quantitation of the relative max intensity of collagen deposition at muscle basement membranes, 5 dpf, (***P < 0.0001), plotted points outside 95% confidence interval analysed by two-way ANOVA, Dunn’s multiple comparisons, from five repeats, box represents 5–95%, median centre line, whiskers = SEM. h Physiological rescue after fibronectin injection. Force transducer measurement of passive tension over stretch load % (n = 5 for each experimental condition) (***P < 0.0001), error bars = SEM.