ANIMAL MODELS FOR LINEAGE TRACING IN (CELL) TRANSDIFFERENTIATION

S. Cinti | Center for The Study of Obesity. Marche Polytechnic University, Ancona, Italy

The cell identity is defined by its anatomy and physiology¹. Our and Other’s data produced in the last decades seem to introduce a new concept in cell biology: the physiologic and reversible transdifferentiation². When a cell is well differentiated the traditional widely accepted concept is that this cell type can only perform the physiologic role dictated by its anatomy. Thus, white adipocytes perform their vital role of storage and distribution of energetic molecules in the intervals between meals. We showed that under cold exposure (both in mice and humans) white adipocytes are able to convert into brown adipocytes changing their anatomy from cells with unilocular into multilocular cytoplasmic fat vacuoles and with a completely different type and number of mitochondria. This type of mitochondria allows new molecular pathways ending in heat production able to counteract the changed environmental conditions³. During pregnancy and lactation, the organism needs to develop structures able to synthesize and secrete milk to guarantee survival of pups. White adipocytes of mammary glands convert into epithelial alveolar glands producing milk. At the end of lactation, they convert back to adipocytes⁴. These extraordinary changes in anatomy and physiology of adipocytes can be followed with different techniques among which lineage tracing is one of the most important. X-Gal histochemistry for the expression of beta-galactosidase plays a key role in this technique.