Fig. 5

Ripply1 knockdown inhibits fast muscle development, dermomyotome maturation is delayed. Control and Ripply1 morphants at the 20-somite (A,B), 22-somite (C,D) and 24-h stage (E-K). (A,B) Ripply1 morphants show upregulation of meox1 (A) and downregulation of pax3 (B) mRNA. (C,D) In control embryos, Tbx6 is restricted to pre-somitic mesoderm, Pax7⁺ dermomyotome cells populate somites 1-18; in Ripply1 morphants, Tbx6 protein is expanded into the posterior trunk, Pax7⁺ cells are restricted to somites <7-14 (D). The Pax7 and Tbx6 expression domains (green and cyan lines, respectively) do not overlap; the dorsal and ventral domains of the trunk develop faster than the central domain (arrowheads). (E-G) At 24h, tbx6 mRNA expression is only slightly expanded in Ripply1 morphants (E); pax3 (F) and pax7 (G) are highly upregulated. (H,I) Immunolabeling shows an increase in Pax7⁺ dermomyotome cells in Ripply1 morphants. Boxes separately show Mef2⁺ (red) and Pax7⁺ nuclei (green, number indicated). (J,K) In wild type, slow muscle fibers (F59, cyan) are found lateral to fast fibers; Ripply1 morphants completely lack fast fibers (red, on cross-sections in J,K), slow fibers lie adjacent to the axial structures. β-catenin labels cell membranes, Hoechst all nuclei. Axis levels of images in H-K are indicated in G. Scale bars: 100µm in B,D,G; 50µm in I,K.