TNFRSF9 and obesity due to melanocortin 4 receptor deficiency: Although CD137 was identified as a marker of beige adipocyte in DNA microarray screens of immortalized cell lines derived from inguinal WAT of a strain of obesity-resistant 129SVE mice (Wu et al. 2012), subsequent studies were unable to validate enrichment of CD137 in beige adipocytes, or increased CD137 expression after cold exposure or adrenergic stimulation in mice (Rosenwald et al. 2013; Srivastava et al. 2020).