Fig. 6

Analysis of the cell autonomy of Hh signaling requirements for Pax7⁺ myogenic precursor regulation. Genetic mosaics were created by transplanting smu(smo)^-/- cells (A–C) or wild-type cells (D–E) into wild-type embryos, embryos were labeled for myosin (MF20, blue) and Pax7 (green). Donor-derived somite cells (red) that are elongated and presumed to be muscle are labeled with asterisks; donor-derived somite cells that are Pax7-positive are indicated with arrowheads. Hh-unresponsive cells were more likely than wild-type cells to maintain Pax7⁺ expression (Table I). (A) Transplanted smu(smo)^-/- somitic cells (red) formed differentiated muscle fibers (arrows) as well patches of cells on the external surface of differentiated muscle fibers (arrowheads) (B) Pax7⁺ myogenic precursor nuclei (green) in the same optical section as panel A. (C) The merged image of panels A and B, showing that patches overlap with several Pax7⁺ nuclei. (D) Transplanted wild-type somitic cells (red) which have differentiated into muscle fibers (arrows) and patches of cells on the external surface of differentiated muscle fibers. (E) Pax7⁺ myogenic precursor nuclei (green) in the same optical section as in panel D. (F) The merged image of panels D and E, showing that the patch of transplanted cells are Pax7⁺ myogenic precursors. All images are single optical sections at the same magnification; anterior to the left, dorsal up; scale bar = 50 μm.