Thermogenic UCP1-positive cells, which include brown and beige adipocytes, transform chemical energy into heat and increase whole body energy expenditure. is found both in the interscapular region as well as in the perirenal area. Beige adipocytes are found interspersed in various white fat depots and their formation can be stimulated by cold exposure or by -adrenergic receptor agonists (Cousin et al., 1992; Young et al., 1984). That brown or beige fat activity confers metabolic benefit is now well established in mice (Cederberg et al., 2001; Cohen et al., 2014; Feldmann et al., 2009; Harms and Seale, 2013; Seale et al., 2011). Imaging and histological analyses have confirmed the existence of UCP1-positive fat in both newborn and adult humans and indicate the presence of both classical brown fat and beige fat (Cypess et al., 2009; Cypess et al., 2013; Lidell et al., 2013; Sharp et al., 2012; van Marken Lichtenbelt et al., 2009; Virtanen et al., 2009). Classical brown and beige adipocytes both express UCP1 and share many morphological and biochemical characteristics, including a well-characterized -adrenergic receptor/cAMP-dependent pathway that regulates thermogenic gene expression. However, multiple lines of evidence have demonstrated that brown and beige adipocytes are in fact distinct cell types. First, classical brown, but not beige adipocytes, arise from a skeletal muscle lineage, Quercetin (Sophoretin) manufacture indicating that there are separate developmental origins for these two cell types (Lepper and Fan, 2010; Sanchez-Gurmaches et al., 2012; Seale et al., 2008). Second, classical brown and beige fat are differentially responsive to various hormonal stimuli or genetic manipulations (Bostrom et al., 2012; Harms and Seale, 2013). Third, classical brown, beige, and Quercetin (Sophoretin) manufacture white adipocytes possess distinct gene expression signatures in cell culture (Wu Quercetin (Sophoretin) manufacture et al., 2012). Despite this progress, a complete molecular description of UCP1-positive adipocytes is still lacking. This is in large part because UCP1-positive adipocytes generally, and beige adipocytes in particular, occur within a complex, heterogeneous mixture of other cell types in adipose tissues. To address the cellular heterogeneity issue, we have adapted translating ribosome affinity purification (TRAP) Quercetin (Sophoretin) manufacture technology (Heiman et Quercetin (Sophoretin) manufacture al., 2008; Sanz et al., 2009). This method, originally developed for neuroscience applications, allows for genetic tagging and isolation of polysomes in a highly cell type-specific manner. Using this approach, we have selectively isolated polysomes of UCP1-positive cells directly from whole adipose tissues in mice. Our studies demonstrate striking similarities and surprising differences between brown and beige cells fate mapping and primary smooth muscle culture experiments provide additional evidence for a smooth PKB muscle-like origin of some beige cells. These results reveal a hitherto unappreciated link between beige fat and smooth muscle-like cells, and provide a powerful foundation for elucidating additional aspects of thermogenic adipocyte function promoter activity to induce Cre expression. Because the recombination event is irreversible and heritable, recombination was minimized in the immediate postnatal period by breeding UCP1-TRAP mice at thermoneutrality and then weaning litters at room temperature. In four-week old mice at room temperature, both UCP1 and eGFP-L10a proteins were principally detected in the classical brown adipose tissue (BAT) but not in subcutaneous or visceral white adipose tissues (Fig. 1B). Next, mice were housed at 4C for an additional two weeks to brown the white fat depots. Under these conditions, induction of both UCP1 and GFP-L10a proteins occurred in.