Figure 2. Hmga2 Knockout Mice Demonstrate Deficiency in Muscle Growth.

(A) Comparison of female Hmga2 knockout (KO) and wild-type (WT) mice at 8 weeks of age. As reported previously, the Hmga2 KO mice have a “pygmy” phenotype, with a body weight of about 40% of WT littermates. *p < 0.05 Hmga2 KO mice versus WT mice. Error bars depict mean ± SEM.

(B) Side-by-side comparison of various tissues including skeletal muscle from Hmga2 KO and WT mice. TA, tibialis anterior; GSP, soleus-gastroc-nemius-plantaris complex; QUAD, quadricep. All organs examined were smaller in Hmga2 KO mice.

(C) The weights of various tissues were normalized to body weight. After normalization, all examined skeletal muscle tissues from Hmga2 KO mice were still significantly smaller than those from Hmga2 WT mice. In contrast, the brain and heart were proportionally larger in Hmga2 KO mice, while the relative weight of liver was almost identical in both genotypes. Consistent with a previous report, Hmga2 KO mice showed depletion of fat tissue, represented by perirenal fat. *p < 0.05 Hmga2 KO mice versus WT mice. Error bars depict mean ± SEM.

(D) Immunofluorescence of Pax7, Laminin, and DAPI on cross-sections of Hmga2 KO and WT mice. Hmga2 KO mice show a smaller cross-section area (CSA) and reduced Pax7 staining. Arrows indicate Pax7+ cells. Scale bar represents 50 μm.

(E) Comparison of CSA from Hmga2 WT and KO mice reveal that Hmga2 KO mice have smaller myofibers. Histogram demonstrates an enrichment of small muscle fibers and lack of big fibers in Hmga2 KO mice versus Hmga2 WT mice.

(F)Hmga2 KO mice had fewer Pax7+ cells per 500 fibers. At least 3,000 fibers were counted for each sample. *p < 0.05 Hmga2 KO mice versus Hmga2 WT mice. Error bars depict mean ± SEM.

See also Figure S3.