Weibel-Palade bodies (WPBs) are cigar-shaped organelles inside endothelial cells and have important roles in haemostasis and inflammation. Crucial to their function is von Willebrand factor (VWF), which is stored in long tubules that run the length of WPBs; VWF is released in response to vascular injury and recruits platelets from the blood to wound sites. On , Daniel Cutler and colleagues use high-pressure freezing and electron microscopy to reveal WPB biogenesis and tubule formation in greater detail than ever before. They show that tubules first become visible inside the trans Golgi network (where VWF multimerisation probably begins) and observe that immature electron-lucent WPBs containing disorganised tubules mature into more orderly and dense organelles. Their observations also indicate that the vesicle coat clathrin has dual roles in WPB formation - both in the formation of WPB and in the removal of missorted material from the maturing organelle. The researchers were also curious about how WPBs are able to move so easily within the crowded endothelial cells. They find that, instead of curving around obstacles, WPBs are able to fold at hinges, and that the rigid vWF tubules are disrupted at these hinge points.
