The AdipoChaser mouse: A model tracking adipogenesis in vivo.

White adipose tissue is considered to have high plasticity. Dynamic, abnormal expansion of white adipose tissue leads to obesity and associated metabolic disorders. Due to technical limitations, the life cycle and turnover rates of different white adipose depots during development and under various physiological conditions and environmental challenges has been assessed only through highly indirect approaches. We have recently described a system for the inducible, permanent labeling of mature adipocytes, the "AdipoChaser" mouse. Utilizing this AdipoChaser mouse model, we found that epididymal fat depots initiate adipogenesis after prolonged high fat diet feeding, whereas subcutaneous fat depots merely undergo hypertrophy and have a very low rate of adipogenesis. During cold exposure or β-3 agonist-induced "browning" of subcutaneous fat depot, most of the beige adipocytes arise from de novo adipogenesis. We also found that cold exposure or β-3 agonist stimulation induces massive white adipogenesis in the epididymal fat depot. Developmentally, adipocytes in the gonadal fat depot are differentiated postnatally, between birth and sexual maturation, while adipocytes in the subcutaneous fat are differentiated between embryonic days 14-18. Our study shed new insights into the developmental aspects of adipose tissue and its dynamics under a number of different physiological challenges.