143 Written by Angela K. Eggleston, Stephane Larochelle & Beth Moorefield unanticipated, but the involved residues on both KRIT1 and ICAP1 are evolutionarily conserved, which points to the likely importance of this interface. Turning to the ICAP1–b1-integrin complex, the b1 tail is seen to bind ICAP1 in the canonical PTB-binding site, consistent with KRIT1 directly competing with b1-integrin for ICAP1 association, a point that is clearly demonstrated by functional analyses. In sum, this study provides a mechanistic understanding of how inactivation of KRIT1, commonly observed in association with CCMs, can result in improper integrin activation, which in turn may contribute to a leaky vasculature. (Mol. Cell doi:10.1016/j.molcel.2012.12.005, published online 10 January 2013) SL Splicing with super 8