• Grega-Larson NE, Crawley SW, Erwin AL, Tyska MJ. Cordon bleu promotes the assembly of brush border microvilli. Molecular biology of the cell. 2015 Sep 9. PMID: 26354418 [PubMed].


Microvilli are actin-based protrusions found on the surface of diverse cell types, where they amplify membrane area and mediate interactions with the external environment. In the intestinal tract, these protrusions play central roles in nutrient absorption and host defense, and are therefore essential for maintaining homeostasis. However, mechanisms controlling microvillar assembly remain poorly understood. Here we report that the multi-functional actin regulator, cordon bleu (COBL), promotes the growth of brush border (BB) microvilli. COBL localizes to the base of BB microvilli via a mechanism that requires its proline-rich N-terminus. Knockdown and overexpression studies show that COBL is needed for BB assembly and sufficient to induce microvillar growth using a mechanism that requires functional WH2 domains. We also find that COBL acts downstream of the F-BAR protein, syndapin-2, which drives COBL targeting to the apical domain. These results provide insight into a mechanism that regulates microvillar growth during epithelial differentiation and hold significant implications for understanding the maintenance of intestinal homeostasis.