Location of CXCL12-expressing cells in developing mesenteries. Sections of E10.5 (A), E11.5 (B), and E12.5 (C) midgut loops from CXCL12/GFP knock-in mice were stained with antibodies against PECAM-1 (red). Images were collected by standard confocal microscopy and optical slices are shown. (B, C) Cells expressing high-level CXCL12/GFP (green) are observed to accumulate in patches adjacent to endothelial cells of SMA (B) and along the sprouts from SMA (C).