Most adult mammalian tissues are quiescent, with rare cell divisions serving to maintain homeostasis. At present, the isolation and study of replicating cells from their in vivo niche typically involves immunostaining for intracellular markers of proliferation, causing the loss of sensitive biological material. We describe a transgenic mouse strain, expressing a CyclinB1-GFP fusion reporter, that marks replicating cells in the S/G2/M phases of the cell cycle. Using flow cytometry, we isolate live replicating cells from the liver and compare their transcriptome to that of quiescent cells to reveal gene expression programs associated with cell proliferation in vivo. We find that replicating hepatocytes have reduced expression of genes characteristic of liver differentiation. This reporter system provides a powerful platform for gene expression and metabolic and functional studies of replicating cells in their in vivo niche.
Bibliographical noteFunding Information:
We thank Ittai Ben-Porath, Shmuel Ben-Sasson, Eithan Galun, Eli Pikarsky, and Gustavo Mostoslavsky for a critical reading of this manuscript, Abed Khalaileh for help in performing partial hepatectomy, and Benzi Zuberi for zygote infection. This work was funded by the Sixth Framework Programme of the European Union and the JDRF Center for Beta Cell Therapy in Diabetes and by an ERC starting grant (to Y.D.). This work was supported in part by a grant from USAID’s American Schools and Hospitals Abroad (ASHA) Program for the upgrading of the Flow Cytometry Laboratory at the Hebrew University Medical School, I-CORE Program of the Planning and Budgeting Committee, and The Israel Science Foundation #41.11.