Fig. 2

Absence of CAPN3 impairs myoblast fusion. Fluorescent images of primary myoblast cultures isolated from 1-month-old CAPN3-KO (a) and WT (b) mice differentiated for 3 days on glass coverslips, fixed and stained for MHC with antibody (green) and DAPI for nucleus. Scale bar = 50 μm. c Fusion index (mean ± SEM). There was a significant reduction in fusion competence between WT (82%) and CAPN3-KO (40%) myoblasts (P < 0.001 by two-tailed t test; data derived from five mice per group; 4–5 frame photographed at 20× per mice were analyzed). CAPN3-KO myotubes were shorter and on average had fewer nuclei than wild type myotubes (d). A total of 246 myotubes from CAPN3-KO and 239 from BL/6 cultures were analyzed. Scattergrams were generated by plotting the number of nuclei for each myotubes. The nuclei density per myotubes was determined and percent distribution histograms (as percent of total myotubes carrying 2 or more nuclei) were generated for comparison (e). ***P < 0.001