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Availibility of Promoter-GFP transgenic mice for identifying subpopulations of cells within the osteoprogenitor lineage.

The stem cell gene anatomy project (SC-GAP, http://www.scgap.org/) sponsored by NIDDK is a consortium of investigators who are sharing methodologies and resources to identify subpopulations of cells within a lineage and to define the molecular profile of the cells as they progress through stages of differentiation.The ultimate goal of the initiativeis to develop and provide these reagents and strategies to the entire cell biology community. This poster will describe the various transgenic mice that are available from this project that are useful in studies of the osteoprogenitor lineage. All of the GFP marker mice are conceptual derivatives of the pOBCol3.6GFP and pOBCol2.3GFP transgenic mice which have been consistent markers of preosteoblast, early osteoblast and late osteoblast differentiation. These transgenes are in CD1 mice and are currently being breed into C57/Bl6 and C3H backgrounds. The Col3.6 construct is available as a GFPtpz, GFPcyan and GFPsaph while the Col2.3 is GFPemd. Previously we reported mice transgenic for the rat 1.7 kb osteocalcin-GFP transgene that showed expression restricted to rare individual osteoblasts and osteocytes in contrast to the wide expression of the Col2.3 transgene in the culture and in intact bone. We have recently generated C57/Bl6 transgenic mice with the human 3.8kb osteocalcin promoter driving GFPtpz. Screening tail biopsies revealed the strong expression of the transgene similar to our pOBCol2.3GFP mice suggesting this will be a strong and widely expressed marker of late osteoblast differentiation. Currently we are examining promoters that may identify cells prior to preosteoblast differentiation. Fibronectin was selected because of its strong expression in developing embryos and its known expression in primary osteoblast cultures. Recently, we have produced two transgenic lines, in which the rat 4.5kb fibronectin promoter drives strong GFPtpz expression in the intervertebral disc region of the tail clips. In marrow stromal cell cultures, this transgene does not activate before pOBCol3.6GFP, and is restricted to large cells at the periphery of the nodule. In the histological sections of adult mice tissues from two different transgenic lines, GFP expression is restricted to cells of nucleus pulposis of the tail vertebral disc without any expression within bone. The value of this transgene for studying bone cell lineage is still under investigation. The progress of this and other constructs will be available through the SC-GAP program will be listed on a web site, http://skeletalbiology.uchc.edu/30_ResearchProgram/304_gap/index.htm.

osteoblast differentiation ; pOBCol3.6/2.3GFP constructs ; fibronectin ; cell cultures ; histology

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