A Novel Fluorescent Marker System Labels Replicating Cells in Vivo

A strain of mice was genetically engineered to express a fluorescent label in cells that were dividing, which allowed them to be isolated and analyzed.

Until now, the isolation and study of replicating cells from living animals typically involved immunostaining for intracellular markers of proliferation, causing the loss of sensitive biological material. This situation has been greatly improved by investigators at the Hebrew University of Jerusalem (Israel) who genetically engineered a line of mice to express a green fluorescent CyclinB1-GFP fusion reporter that marked replicating cells in the S/G2/M phases of the cell cycle. The green color disappeared upon completion of cell division.

The investigators employed flow cytometry to isolate live replicating cells from the livers of the genetically engineered mice and compared their transcriptome to that of quiescent cells to reveal gene expression programs associated with in vivo cell proliferation.

They reported in the September 20, 2012, online edition of the journal Developmental Cell that replicating hepatocytes had reduced expression of genes characteristic of liver differentiation. Thus, in the replicating liver cells there was a significant decrease in the expression of genes responsible for key liver functions such as fatty acid and amino acid metabolism.

The investigators concluded that when differentiated cells divide, they temporarily shift to a less differentiated state. This condition is similar to that of cancer cells, which are less differentiated than normal cells and proliferate rapidly.

The fluorescent cell replication reporter system was shown to provide a powerful platform for gene expression and metabolic and functional studies of dividing cells in their in vivo niche.

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Hebrew University of Jerusalem