We report the first case of nonimmune hydrops fetalis (NIHF) associated with a recessive, in-frame deletion of V205 in the G protein–coupled receptor, Calcitonin Receptor-Like Receptor (hCALCRL). Homozygosity results in fetal demise from hydrops fetalis, while heterozygosity in females is associated with spontaneous miscarriage and subfertility. Using molecular dynamic modeling and in vitro biochemical assays, we show that the hCLR(V205del) mutant results in misfolding of the first extracellular loop, reducing association with its requisite receptor chaperone, receptor activity modifying protein (RAMP), translocation to the plasma membrane and signaling. Using three independent genetic mouse models we establish that the adrenomedullin–CLR–RAMP2 axis is both necessary and sufficient for driving lymphatic vascular proliferation. Genetic ablation of either lymphatic endothelial Calcrl or nonendothelial Ramp2 leads to severe NIHF with embryonic demise and placental pathologies, similar to that observed in humans. Our results highlight a novel candidate gene for human congenital NIHF and provide structure–function insights of this signaling axis for human physiology.
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Funding: NIH grants RO1-DK099156, RO1-HD060860, and RO1-HL129086 to K.M. Caron.; American Heart Association Innovator Award 16IRG27260077 to K.M. Caron; NIH grant F32-HL134279 to D.I. Mackie.; American Heart Association grant 15POST25270006 to R.B. Davis; NIH grant F31-CA174194 to D.O. Kechele, Biotechnology and Biological Sciences Research Council grant BB/M007529/1 to D.R. Poyner and J. Simms. NIH NCI K12 Training Grant 5K12-CA100639-10 and NIH NCI grant 1K22CA212058-01 were awarded to J.C. Snyder. National Institute of Drug Abuse grant 5P30-DA029925-06 to was awarded to M.G. Caron.