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Figure 3 Styxl2 is not required for sarcomere maintenance but involved in de novo sarcomere assembly in adult muscles. (A) The schematic to assess the role of Styxl2 in sarcomere maintenance in adult muscles. TMX: tamoxifen. (B) Styxl2 protein levels in control (Ctrl) and myofiber-specific Styxl2 knockout (MF-iKO) mouse gastrocnemius muscles used for force test. The band intensity of Styxl2 was quantified by ImageJ. (C, D) The twitch and tetanic force generated by gastrocnemius muscles of three Ctrl and four MF-iKO mice were measured. In (A?D), Ctrl: Styxl2f/f mice; MF-iKO: Tg: HSA-MerCreMer; Styxl2f/f mice. (E) The schematic to assess the role of Styxl2 in de novo sarcomere assembly in adult muscles. CTX: cardiotoxin. (F) Styxl2 protein levels in regenerated gastrocnemius muscles used for force test. N.S.: non-specific. The band intensity of Styxl2 was quantified. (G, H) Twitch and tetanic force by regenerated gastrocnemius muscles were measured from four pairs of control and MuSC-specific Styxl2 KO (SC-iKO) mice. (I) Transmission electron microscopy (TEM) images of the muscle used for force generation test. Scale bar: 500 nm. (J) Quantification of sarcomere length in (I). TEM images from three pairs of mice were examined and the length of 3?5 sarcomeres from each mouse was measured. In (E?J), Ctrl: Pax7CreERT2/CreERT2 mice; SC-iKO: Pax7CreERT2/CreERT2; Styxl2f/f mice. n.s.: not significant. *p-value <0.05. ***p-value <0.001.