Figure 5.

Rab13 is expressed in rat long bones in vivo. Rat long bones were processed for immunohistochemistry as described in the Materials and Methods. Sequential slices were incubated without primary antibody (A), with anti-cathepsin K antibody to indicate osteoclasts (B), or with anti-Rab13 antibody (C, D). Rab13 staining was restricted to the superior part of osteoclasts, excluding the ruffled border, whereas strong labeling of cathepsin K was detected also at the lower parts of osteoclasts (arrowheads). Asterisks mark the bone matrix under the osteoclasts. Some of the mononuclear cells in the bone marrow were also Rab13-positive. Rat osteoclasts were purified from bone marrow of newborn rat long bones by magnetic separation using the vitronectin receptor antibody, lysed, and immunoblotted with anti-Rab13 antibody. Rab13 expression was detected in both fractions, osteoclasts (OC) and non-osteoclasts (Non-OC) (E). Equal amounts of total protein were loaded per lane (15µg).