a) Section of Diaphragm muscle from double heterozygous Tg:TN-AP-CreERT2:R26R mice stained for β-gal (blue) and grey (red) 72 h after tamoxifen injection. Double-positive β-gal+/AP+ vessels are clearly visible. High magnification in the inset. Scale bar, 100 μm. ( b, c) X-gal whole-mount staining of Diaphragm ( b) and Quadriceps ( c) from Tg:TN-AP-CreERT2:R26R mice, 72 h after last tamoxifen injection. ( d– k) Tg:TN-AP-CreERT2:R26 NZG Triceps muscle sections, 72 h after tamoxifen injection, stained with X-Gal and antibodies specific for the endothelial or pericyte lineages. ( d, e) Two β-gal+/Pecam+ endothelial cells are visible (arrows). Pecam is stained in red, nuclei are counterstained with DAPI. Scale bar, 20 μm. ( f, g) Two β-gal+/PDGFRβ+ pericytes surrounding a small vessel. PDGFRβ is stained in green, nuclei are counterstained with DAPI. Scale bar, 20 μm. ( h– k) A β-gal+/NG2+ pericyte surrounding a small vessel. Note that the pericyte is negative for the endothelial marker Pecam. NG2 is stained in green; Pecam in red; nuclei are counterstained with DAPI. Scale bar: 20 μm. ( l) Distribution of β-gal+ cells within the endothelial and pericyte populations for the Diaphragm muscle; 500 β-gal+ cells were analysed. ( m, n) Single fibre preparation from Tg:TN-AP-CreERT2:R26R-EYFP TA muscle cultured for 5 days with 4-OH tamoxifen and stained with anti-MyoD (red) and anti-GFP antibodies (green); DAPI in blue. No YFP+ cells were found in purified fibre preparations. Scale bars, 50 μm ( o, p) Nonpurified cell suspension of TA muscle from Tg:TN-AP-CreERT2:R26R-EYFP mice, cultured for 5 days with 4-OH tamoxifen and stained for MyoD (red) and GFP (green); DAPI in blue. Scale bars, 50 μm.