Fig 1: Expression levels and spatial expression of CSRP3 and MURC in shPab muscles. A Paired dot-plots show the normalized (median subtracted) mass spectrometry abundances of CSRP3, MURC, tubulin, and actin in control and shPab muscles. A statistical difference was assessed with a paired ratio t-test. (N = 4 mice). B Western blots show expression levels in paired muscles. GAPDH was used as loading control. PABPN1 level confirms down-regulation. Full-length blots are presented in Fig. S10. C Spatial localization of CSRP3 in control and shPab muscles. Images from a representative region in tibialis anterior muscle, show MyHC-2B and MyHC-2A transitions between control and shPab. Staining shows CSRP3 in red, MyHC isoforms type-2A in blue and type-2B in green. The merged image shows CSRP3 enrichment in type-2A myofibers. Scale bar is 50 µm. Transparent line indicates area used for distribution plots. D Distributions plot shows the mean fluorescence intensity of CSRP3 (in red), MyHC-2A (blue) and MyHC-2B (green). Upper panel corresponds to the transparent line found in the control merged image and lower panel for the transparent line found in shPab merged image. E Table indicates a Pearson correlation assessment of CSRP3 mean fluorescence intensity with myosin heavy chain MFI. MFI of CSRP3 and MyHC-2A and -2B was measured from all myofibers in cross-sections of control (210myofibers) and shPab (300myofibers) muscles. F Spatial localization of MURC in shPab muscles. Upper panel shows representative images in tibialis anterior: MURC is depicted in red and DAPI nuclear counterstaining in cyan. MURC staining in central nuclei is shown in the fluorescence distribution plot. Arrows point to central nuclei. Scale bar is 25 µm. Lower panel shows intensity distribution of MURC and DAPI along the white line (in the upper panel) peripheral nuclei and depicted with P, and central nuclei with C. G MURC signal in a myofiber splitting initiation (left, depicted by arrows) in shPab muscle. The same regions are indicated by arrows in a differential interference contrast (DIC) image (right). Scale bar is 15 µm.