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Blood Advances From the cover. Bergmeier lab image has been selected for the cover of Blood Advances 1:18 issue.

Bergmeier Blood Advances cover

The Bergmeier lab studies the biology of platelets and their precursor cells, megakaryocytes. Special credit for this cover image goes to Dorsaf Ghalloussi, who established the required imaging technique in the lab, and David Paul, the lead author of the study who acquired the image.

In the image you see blood vessels in red, megakaryocytes and platelets in green, nuclei in blue – image from a bone marrow whole mount.
Brief description of the science
The actin cytoskeleton is a key regulator of various cellular functions. To examine the role of the Arp2/3 complex, an essential component in actin filament branching, in platelet biology, Bergmeier lab analyzed mice lacking the p34 subunit of the Arp2/3 complex specifically in platelets and their precursor cells, megakaryocytes. Deletion of the Arp2/3 complex in mice resulted in marked microthrombocytopenia (smaller and fewer platelets), a finding that is consistent with the very recent description of microthrombocytopenia in patients with defects in the Arp2/3 complex. Bergmeier lab mechanistic studies demonstrate that the decrease in circulating platelets is due to altered platelet release in the bone marrow and impaired platelet survival in circulation. Arp2/3 deficient platelets exhibited alterations in their actin cytoskeleton and their peripheral microtubule coil, changes that may contribute to faster clearance of these cells by macrophages of the spleen and the liver. Arp2/3 deficient platelets failed to spread and showed a mild defect in integrin-mediated aggregation. However, these mild functional defects did not impair the ability of these cells to prevent blood loss at sites of vascular injury. In summary, Bergmeier lab studies identify a critical role for the Arp2/3 complex, and thus actin filament branching, in platelet release from megakaryocytes and platelet survival in circulation.