Figure 4

Energy stress results in reduced muscle fiber and increased myofibril (sarcomere) area in P10 smPit^−/−; smPit/2^−/− mice. (A) smPit1^−/−; smPit2^−/− mice showed a reduction of quadriceps fiber area at P10 in paraffin sections stained with H&E. (B) smPit1^−/−; smPit2^−/− mice showed an increased gastrocnemius myofibril (sarcomere) area at P10 in TEM. A and B show arbitrary units following ImageJ analysis of these sections on the y-axis. (C) Semi-quantitative RT-PCR showed reduced expression of myoblast markers myogenin, Pax7 and fast twitch Myh4 myosin in P10 quadriceps muscle of smPit1^−/−; smPit2^−/− mice (D) Densitometric analysis of an immunoblot (Fig. S4A) showing increased pAMPK/tAMPK ratio and reduced pERK1/2/tERK1/2 ratio in quadriceps of four different smPit1^−/−; smPit2^−/− mice at P10. (E) Mitochondrial area and size distribution in TEM of GC at P10. (F) Semi-quantitative RT-PCR to determine gene expression of Xpr1 and PiC transcription factors and metabolic markers in quadriceps muscle of smPit1^−/−; smPit2^−/− mice at P10. Shown are means ± SEM, n = 3–10, ^****p < 0.00002, ^***p = 0.0002, ^**p = 0.002, ^*p = 0.03 vs. WT.