Figure 2.

Tracking de novo adipocyte differentiation using the MuralChaser model. (A) Genetic alleles comprising the MuralChaser lineage tracing system. In the presence of doxycycline (DOX), rtTA activates Cre expression. Cre excises the loxP-flanked membrane tdTomato cassette and allows constitutive activation of membrane GFP (mGFP) reporter expression. (B) “Pulse-chase” lineage tracing approach. Doxycycline-containing food was administered to MuralChaser mice for 9 d to label Pdgfrβ⁺ cells (“pulse”). Animals were then switched to a high-fat diet (HFD) or chow diet for 8 wk in the absence of doxycycline (chase). mGFP⁺ adipocytes represent de novo differentiated fat cells formed during the 8-wk period. (C,D) Administration of doxycycline to MuralChaser mice for 9 d resulted in doxycycline-dependent mGFP labeling (arrowhead) of Pdgfrβ⁺ cells lining the endothelium (CD31⁺) of adipose tissue (“pulse”). (E,F) mGFP labeling was not found in mature adipocytes (perilipin⁺). (G,H) Following 8 wk of high-fat diet feeding, numerous mGFP⁺ perilipin⁺ adipocytes were observed (arrows). These cells represent de novo differentiated adipocytes formed during the 8-wk period. Portions of this figure were reproduced with data from Vishvanath et al. (2016), with permission from Elsevier.