Calcitonin receptor-like receptor guides arterial differentiation in zebrafish

The calcitonin receptor-like receptor (crlr) is a major endothelial cell receptor for adrenomedullin, a peptide vasodilator involved in cardiovascular development, homeostasis, and disease. Here, we used the zebrafish (Danio rerio) model to characterize the role of crlr in vascular development. Crlr is expressed within somites from the 4- to the 13-somite stage and by arterial progenitors and axial vessels during zebrafish development. Loss of crlr results in profound alterations in vascular development and angiogenesis, including atrophic trunk dorsal aorta and interruption of anterior aortic bifurcation, delay in intersomitic vessel development, and lack of blood circulation. Remarkably, crlr morphants are characterized by the loss of arterial endothelial cell identity in dorsal aorta, as shown by the lack of expression of the arterial markers ephrin-B2a, DeltaC, and notch5. Down-regulation of crlr affects vascular endothelial growth factor (vegf) expression, whereas vegf overexpression is sufficient to rescue arterial differentiation in crlr morphants. Finally, genetic and biochemical evidences indicate that somitic crlr expression is under the control of sonic hedgehog. These data demonstrate that crlr plays a nonredundant role in arterial differentiation, representing a novel element of the sonic hedgehog-vegf-notch signaling cascade that controls arterial/venous fate.