Fig. 1.
Phenotypes of muscle-specific Rpt3-knockout mice. (A) Generation of the Rpt3−/− mice. Mlc1f-Cre+/−/Rpt3f/− mice were mated to produce mlc1f-Cre+/−/Rpt3+/+ mice and mlc1f-Cre+/−/Rpt3f/f mice (referred to as Rpt3+/+ mice and Rpt3−/− mice, respectively). (B) Muscle homogenates were immunoblotted with antibodies against Rpt3 and Hsp90. Rpt3 protein was nearly undetectable in the homogenate of gastrocnemius (GC) from Rpt3−/− mice. The homogenate from soleus muscle gave a similar result. Quantitative data are also presented (n = 3). White bar, Rpt3+/+ mice; gray bar, Rpt3−/− mice. SOL, soleus; AU, arbitrary units. (C) The general appearance of Rpt3−/− mice is shown. Note the smaller body frame and kyphosis in Rpt3−/− mice. (D) The body weights of Rpt3+/+ and Rpt3−/− mice are shown (n = 10 and 11, respectively). Note that the difference in the body weight became prominent after 3 weeks of age. Open circles, Rpt3+/+; closed squares, Rpt3−/−. (E) Kaplan–Meier survival curves for Rpt3+/+ and Rpt3−/− mice (n = 46 each). (F) Appearance of excised skeletal muscles of Rpt3+/+ and Rpt3−/− mice. TA, tibialis anterior. Scale bar: 1 cm. (G) Absolute skeletal muscle weight (mg) was significantly different between Rpt3+/+ and Rpt3−/− mice in tibialis anterior, gastrocnemius and soleus muscles (n = 10). White bars, Rpt3+/+; gray bars, Rpt3−/−. (H) Skeletal muscle weight (mg)/body weight (g) were significantly different between Rpt3+/+ and Rpt3−/− mice in tibialis anterior and gastrocnemius muscles (mostly fast-twitch fibers) but not in soleus muscle (half of the fibers are slow-twitch) (n = 10). (I) Heart weight (mg)/body weight (g) was not significantly altered in the Rpt3−/− mice. (J) Grasping power (kg)/body weight (g) was significantly lower in the Rpt3−/− mice (n = 5). (K) Creatine kinase (CK; IU/l) was significantly higher in the Rpt3−/− mice (n = 5). (L) The step length (mm) was significantly shorter in Rpt3−/− mice compared with Rpt3+/+ mice (n = 5). Quantitative data show the mean+s.e.m.; *P<0.05; n.s., non-significant [Student's t-test (B,G–I,K,L); Mann–Whitney U test (J)].