Fig. 5. Smooth muscle-like origin of beige cells.

(A) Schematic of the cross to generate Myh11-GFP/tdTomato reporter mice. Transgenic mice expressing a bicistronic transgene consisting of Cre and eGFP under the control of 16 kb of the Myh11 promoter were crossed with tdTomato reporter mice. (B) GFP immunofluorescence and endogenous tomato fluorescence in the iWAT pad. Representative reporter mice (Cre-positive, tomato-positive) and control mice (Cre-negative, tomato-positive) are shown. (C–E) Perilipin (C) or UCP1 (D and E) immunofluorescence and endogenous Tomato fluorescence in iWAT (C and D) or BAT (E). (F) Quantification of double tdTomato+; UCP1+ cells as a percentage of total UCP1-positive cells from iWAT and BAT of Myh11-GFP/tdTomato reporter mice. Data are shown as means ± standard error; n = 3 mice per group. * p < 0.05 for iWAT versus BAT. (G) Schematic of the cross to generate Myh11-CreERT2/GFP reporter mice. BAC transgenic mice expressing a CreERT2 allele under the control of the Myh11 promoter were crossed to GFP (ROSA^mT/mG) reporter mice. (H) Cartoon depicting the time course for tamoxifen injections, the washout period, and cold exposure. Tamoxifen was injected at 2 mg/mouse/day for four consecutive days prior to the washout period. (I, J) Immunohistochemical staining of tissues from day 25 for UCP1 (left panels) or GFP (right panels) in the iWAT (I) or BAT (J) of Myh11-CreERT2/GFP reporter mice. For both reporter experiments, mice were heterozygous for Cre and heterozygous for the reporter gene. For B–F, representative images were taken in 6-week old female Myh11-GFP/tdTomato reporter mice following two weeks cold exposure at 4°C. For I–J, representative images were taken in 8-week old male Myh11-CreERT2/GFP reporter mice following the treatment scheme indicated in (H).