Abstract 054: Mutations In Pde3a Explain Mendelian Hypertension With Brachydactyly

We identified Mendelian type E brachydactyly (BDE) with hypertension in six different families from Turkey, America, France, Canada and South Africa. The two phenotypes, hypertension and BDE, invariably coincide. The blood pressure in affected individuals increases with increasing age, the mean arterial blood pressure at 50 years exceeds 150 mm Hg, resulting in stroke. Earlier we suggested that a chromosomal rearrangement on 12p could be responsible. We now used whole-genome sequencing and discovered six different so far unknown missense mutations in the gene encoding PDE3A. The mutations are not identical, but adjacent to each other. Each is responsible for an amino acid substitution in a conserved portion of the protein. The mutations were not present in any non-affected family members, in more than 200 additional controls, and not found in the “1000 genome” project. We performed in vitro cell transfections and found that mutated PDE3A showed gain-of-function with increased cAMP hydrolysis. Mesenchymal stromal cell-derived vascular smooth muscle cells and chondrocytes gave insight into the molecular pathogenesis; PDE3A and vasodilator-stimulated phosphoprotein (VASP) were differently phosphorylated and parathyroid hormone-related peptide (PTHrP) was dysregulated. Our preliminary results reveal that the mutated PDE3A enzymes show gain-of-function with increased cAMP hydrolysis and sensitivity to cGMP inhibition. We suggest that the mutations are responsible for both phenotypes. This Mendelian hypertension is the first that is not attributable to increased sodium reabsorption in the distal nephron.