Figure 3.

Expression of CXCR4, Lbx1, and MyoD in limb muscle progenitors. (A-D) Sections of the forelimb of E10.25 (A,D), E10.75 (B), and E11.25 (C) mouse embryos stained with anti-CXCR4 (red) and anti-Lbx1 (green) antibodies. CXCR4⁺ and Lbx1⁺ cells are present in the muscle masses, and analysis at high magnification demonstrates that they are present in the same cells. (D) Note that not every Lbx1⁺ cell expressed CXCR4, but all CXCR4⁺ muscle progenitor cells were also positive for Lbx1. (A) In addition, CXCR4 was also present in limb endothelial cells (arrowhead). (E,F) Section of the forelimb of mouse embryo at E10.25 (E) and E11.25 (F) stained with anti-CXCR4 (red) and anti-MyoD (green) antibodies. CXCR4⁺/MyoD⁺ double-positive cells were very rare. (G) Schematic representation of gene expression in developing muscle progenitors. CXCR4 expression is induced after muscle progenitors have delaminated and have reached the limb, and is extinguished prior to their differentiation. Bars: A-C,E-F, 250 μm; D, 30 μm.