Figure 1.

The Absence of Wild-Type Endogenous Mouse COMP Decreases MT-COMP Intracellular Retention and Chondrocyte Death

(A–I) Human COMP-specific (A–D) and TUNEL (E–H) immunostaining of P28 growth plates from control (C57BL\6), COMP^−/−, MT-COMP (MT-COMP/COMP^+/+), and MT-COMP/COMP^−/− mice is shown. DAPI (blue) was used to visualize nuclei. Growth plates from at least eight mice from each genotype were examined in each group. No human COMP is observed in either the control (C57BL\6) or COMP^−/− growth plate (A and B). MT-COMP intracellular retention is decreased in the absence of endogenous mouse COMP (compare D with C). TUNEL staining is present in only a few chondrocytes of control mice (E), whereas, in the MT-COMP growth plate, most chondrocytes are TUNEL-positive (G). TUNEL staining is markedly decreased in the MT-COMP/COMP^−/− mouse growth plate (compare H with G and I).