Developmental origin of adipocytes: new insights into a pending question.

The current epidemic of obesity has caused a surge of interest in the study of adipose tissue formation. Much progress has been made in defining the transcriptional networks controlling the terminal differentiation of preadipocytes into mature adipocytes. However, the mechanisms that direct MSCs (mesenchymal stem cells) down the adipocyte lineage remain largely unknown. Similarly, although adipocytes are generally described to derive from mesoderm, the study of the developmental origin of MSCs and adipose tissues has been largely disregarded until now. Functional variations do exist between different adipose tissues, which suggest possible differences in their developmental origin and might explain why some depots are more associated than other to metabolic disorders. This review summarizes the surprising findings that have recently emerged from both embryonic stem cells and lineage-tracing studies in vivo, unravelling an unsuspected developmental origin for MSCs and adipocytes in the neural crest.