Regulated storage of type 2A variants in HEK293 cells. (A) Type 2A variants were expressed homozygously in HEK293 cells, immunostained, and examined by confocal microscopy, as described in “Immunofluorescent staining.” C1190S (not shown), C1099P, C1272Y, I1568N, and G1579R (ii, iv, vii, and viii, respectively) formed Weibel-Palade body–like storage granules, similar to WT-VWF (A). Variants C1272S, L1503R, S1506L,G1631D (iii, v, vi, and ix) and V1607D (not shown) demonstrated a loss of regulated storage, as indicated by the lack of storage granules and the diffuse staining pattern. (B) Type 2A variants were coexpressed in a 1:1 ratio with WT-VWF in HEK293 cells, immunostained, and examined by confocal microscopy, as described in “Immunofluorescent staining.” Cells expressing both WT-VWF and S1506L (i-iii) demonstrated a loss of Weibel-Palade body–like granules. Cells expressing WT-VWF and G1631D (iv-vi) formed less-elongated granules. WT-VWF storage was not disrupted when cotransfected with I1568N (vii-ix). Regulated storage was disrupted for some type 2A variants.