Novel type II collagen reporter mice: New tool for assessing collagen 2α1 expression in vivo and in vitro

We report the generation of a new mouse strain harboring a Col2‐pd2EGFP reporter transgene; pd2EGFP has a much shorter half‐life than EGFP, making it a near real‐time reporter for Col2α1 expression in vivo and in vitro. In the post‐natal growth plate, pd2EGFP fluorescence was expressed in almost all proliferative chondrocytes and in some hypertrophic chondrocytes based on localization with type X collagen. In articular cartilage, pd2EGFP fluorescence diminished over time, nicely illustrating the decrease of type II collagen synthesis in articular chondrocytes during growth. Monolayers of FACS‐sorted chondrocytes from P1‐2 mice showed faster loss of pd2EGFP compared to EGFP, reflecting rapid chondrocyte de‐differentiation. High‐density culture of FACS‐pd2EGFP‐ growth plate chondrocytes revealed the typical temporal expression pattern in which type II collagen preceded type X collagen matrix deposition. The Col2‐pd2EGFP reporter mouse will be a valuable tool for studies of growth plate chondrocyte biology. Developmental Dynamics 240:663–673, 2011. © 2011 Wiley‐Liss, Inc.