Stage-and tissue-specific expression of a Col2a1-Cre fusion gene in transgenic mice

To achieve chondrocyte-specific deletion of flexed genes we generated a tra nsgenic mouse line expressing the Cre recombinase under the control of the mouse type II collagen gene (Col2a1) regulatory regions. Northern and in si tu hybridization analyses demonstrated the expression of the transgene (Col 2a1-Cre) in cartilaginous tissues. To test the excision efficiency of Cre, the Col2a1-Cre strain was crossed with the ROSA26 reporter strain. LacZ sta ining of double transgenic mice revealed Cre activity in both chondrogenic and non-chondrogenic tissues. During early embryonic development (E9.5-11.5 ), LacZ expression was detected in tissues where the endogenous Col2a1 tran script is expressed such as the otic capsule, notochord, developing brain, sclerotome and mesenchymal condensations of future cartilage. At later stag es, Cre activity was observed in all cartilaginous tissues with virtually 1 00% of chondrocytes being LacZ positive. These data suggest that the Col2a1 -Cre mouse strain described here can be useful to achieve Cre-mediated reco mbination in Col2a1 expressing cells, especially in chondrocytes. (C) 2001 Elsevier Science B.V./International Society of Matrix Biology. All rights r eserved.