In addition, the reciprocal signaling between EphrinB2 (artery specific gene) and its receptor EphB4 (vein specific gene) is critical for the formation of capillary beds [10], and it is proposed that a defect in ephrins or their receptors may be a causative factor in the formation of Arteriovenous Malformation (AVM) [11]. The gene discussed is EPHB4; the disease is arteriovenous hemangioma/malformation.