SLC35D3 is depleted in platelets from ash-Roswell mice and mouse models of HPS2 and HPS9, but not of HPS4. Lysates of platelets isolated from wild-type and disease model platelets were fractionated by SDS-PAGE and analyzed by immunoblotting with Abs to SLC35D3 or to actin as a control. Relevant regions of the immunoblot are shown with positions of molecular weight markers (left) and specific SLC35D3 and actin bands indicated by lines (right). (A) SLC35D3 (detected with unfractionated antiserum) is absent from Slc35d3^ros/ros platelets. Lysates from platelets isolated from 3 control C3H/HeSnJ (wild-type) and 3 Slc35d3^ros/ros mice were analyzed. Note that background bands (M_r approximately 55 000) were present in all lysates. (B) SLC35D3 (detected with affinity-purified Ab) is reduced in platelets of HPS2 and HPS9 mouse models. Lysates of platelets from wild-type C57BL/6J and congenic pallid (Pa; BLOC-1–deficient HPS9 model), pearl (Pe; AP-3–deficient HPS2 model), and light ear (Le; BLOC-3–deficient HPS4 model) mice were analyzed. Note the marked depletion of SLC35D3 from both pallid and pearl, but not light ear platelets. (C) SLC35D3 band intensities were measured from at least 3 replicates of blots as in panel B, normalized to actin levels for each lysate, and then expressed as the percentage (mean ± SD) of the mean normalized value for wild-type lysates. The normalized values for HPS models were evaluated relative to normalized wild-type by unpaired 2-tailed Student t test. ****P < .0005; ***P < .001.