Figure 7. A scheme describing the molecular interactions between Mp, Slit/Robo and F-actin in the heart and the aorta.

A- Heart-specific expression of Mp that is restricted to the luminal membrane, promotes the formation of Mp-Slit complex facilitating Slit/Robo activity, leading to the formation of Slit endocytic vesicles close to the luminal membrane. Slit/Robo signaling reduces F-actin levels at the luminal membrane, and restricts the junctional domain by promoting Armadilo turn over. Reiterated Slit/Robo signaling is maintained as a result of continued Mp expression and its association with newly secreted Slit, leading to inward curving of the luminal membrane. B- Lack of Mp in the aorta limits Slit/Robo activation, leading to a significantly narrow lumen.