Fig. 3: Loss of PRR33 reduces the size of myofibers in vivo and results in a decrease in muscle strength.

A The genetic model in which Prr33 was abrogated in skeletal muscle. HSA: Human skeletal α-actin. B mRNA level of Prr33 in mouse muscle samples including TRI, QUAD, GAS and TA assessed by qRT-PCR. TRI Triceps muscle, QUAD: Quadriceps femoris muscle, GAS Gastrocnemius muscle, TA Tibialis anterior muscle. Data was presented as mean ± SEM. (Student’s t-test). Prr33^fl/fl: N = 4; Prr33^KO: N = 6. C The ratio of muscle weight to body weight in Prr33^fl/fl and Prr33^KO mice. Data was presented as mean ± SEM. (Student’s t-test). Prr33^fl/fl: N = 11; Prr33^KO: N = 8. D WGA staining of TA muscle section of Prr33^fl/fl and Prr33^KO mice (4-week-old). Prr33^fl/fl: N = 7; Prr33^KO: N = 5. Bar: 150 μm. E Zoomed-in images of the regions (white squares) showed in Fig. 3D. Bar: 20 μm. F Myofiber size in the cross-section areas (CSA) of TA myofibers from Prr33^fl/fl or Prr33^KO mice were analyzed at 4 weeks after birth using ImageJ software (https://imagej.nih.gov/ij/). Prr33^fl/fl: N = 7; Prr33^KO: N = 5. G Myofiber size distribution in the cross-section areas of TA muscle in Prr33^fl/fl and Prr33^KO mice at 4 weeks after birth. Prr33^fl/fl: N = 7; Prr33^KO: N = 5. Myofiber size was measured with ImageJ. H Myofiber size in the cross-section areas (CSA) of QUAD myofibers from Prr33^fl/fl and Prr33^KO mice were analyzed at 4 weeks after birth using ImageJ software (https://imagej.nih.gov/ij/). Prr33^fl/fl: N = 7; Prr33^KO: N = 5. I Myofiber size distribution of the cross-section areas of QUAD muscle in Prr33^fl/fl and Prr33^KO mice at 4 weeks after birth. Prr33^fl/fl: N = 7; Prr33^KO: N = 5. Myofiber size was measured with ImageJ. J Muscle endurance analysis for Prr33^fl/fl and Prr33^KO mice by running wheel assay. Endurance time data was documented and presented as mean ± SEM in the graph. (Student’s t-test). Prr33^fl/fl: N = 4; Prr33^KO: N = 4. K Limb grip strength measurement of Prr33^fl/fl and Prr33^KO mice. Data was presented as mean ± SEM. (Student’s t-test). Prr33^fl/fl: N = 4; Prr33^KO: N = 4.