Figure 3.

Electron microscopy of osteoclasts in TRAF6^−/− and TRAF6^+/− mice. (A) TRAF6^+/− osteoclast seen in a resorption lacuna. The depicted cell exhibits an attachment zone (asterisk), cytoplasmic vacuolization, and ruffled border (arrowhead), features of a normally activated, mineral-resorbing (arrow) osteoclast. (B) This cell illustrates the typical osteoclast in TRAF6^−/− mice. There is no evidence of activation or mineral resorption, the cell forms no attachment zone or ruffled border (arrowhead), and is in limited contact with the underlying bone. (C) One of the few activated osteoclasts in a TRAF6^−/− mouse. The cell is in contact with the mineralized bone, forms an adhesion zone (asterisk), and has a partial and disorganized ruffled border (large arrowhead). Some resorption is occurring as evidenced by the dissolved bone material (arrow) and the cytoplasmic vacuolization of the cell. However, on most of the bone surface covered, there is no ruffled border formation and no bone resorption (line of arrowheads). Size bar, 5 μm.