Figure 4.

Mylk4 KO mice showed decreased isometric torque and passive stiffness mediated by phosphorylation of MYOM1

(A) Strategy for generation of Mylk4 KO mice #1 and #2 by the Cas9 system.

(B) Sequence of mRNA and protein of Mylk4 KO mice #1 and #2.

(C–E) Body weight (C), gastrocnemius muscle (Gas) weight (D), and maximum isometric torque (MIT) of in situ plantar flexion (E) were measured in 10-week-old female WT (n = 10) and Mylk4 KO mice (n = 8). ∗P < 0.05.

(F) Post-tetanic potentiation of in situ plantar flexion was measured in 10-week-old female WT (n = 5) and Mylk4 KO mice (n = 3).

(G) Proteomic strategy for substrate identification.

(H) Phosphorylated proteins were enriched from WT and Mylk4 KO mice and analyzed by SDS-PAGE.

(I) Active force and passive stiffness were measured with chemically skinned fibers from tibialis anterior muscles of 10-week-old female WT (active force, n = 28; passive force, n = 23) and Mylk4 KO mice (active force, n = 20; passive force, n = 24). ∗∗∗P < 0.001, ∗∗∗∗P < 0.0001. Two-tailed, unpaired Student's t tests. Data are represented as mean ± standard deviation.

See also Figures S6–S8.