Search

Background: High blood pressure is the primary risk factor for cardiovascular death worldwide. Autosomal dominant hypertension with brachydactyly clinically resembles salt-resistant essential hypertension and causes death by stroke before 50 years of age. We recently implicated the gene encoding phosphodiesterase 3A ( PDE3A ); however, in vivo modeling of the genetic defect and thus showing an involvement of mutant PDE3A is lacking. Methods: We used genetic mapping, sequencing, transgenic technology, CRISPR-Cas9 gene editing, immunoblotting, and fluorescence resonance energy transfer. We identified new patients, performed extensive animal phenotyping, and explored new signaling pathways. Results: We describe a novel mutation within a 15 base pair (bp) region of the PDE3A gene and define this segment as a mutational hotspot in hypertension with brachydactyly. The mutations cause an increase in enzyme activity. A CRISPR/Cas9-generated rat model, with a 9-bp deletion within the hotspot analogous to a human deletion, recapitulates hypertension with brachydactyly. In mice, mutant transgenic PDE3A overexpression in smooth muscle cells confirmed that mutant PDE3A causes hypertension. The mutant PDE3A enzymes display consistent changes in their phosphorylation and an increased interaction with the 14-3-3θ adaptor protein. This aberrant signaling is associated with an increase in vascular smooth muscle cell proliferation and changes in vessel morphology and function. Conclusions: The mutated PDE3A gene drives mechanisms that increase peripheral vascular resistance causing hypertension. We present 2 new animal models that will serve to elucidate the underlying mechanisms further. Our findings could facilitate the search for new antihypertensive treatments.

Microscopic hematuria is a common feature of patients with Alport syndrome, a familial nephropathy due to mutations in COL4A3, COL4A4 or COL4A5. These genes encode for α3, α4, and α5 type IV collagen polypeptide chains (collagen IV α345), crucial for the structural component of the glomerular basement membrane. Even patients with mild phenotype, namely isolated microhematuria (X-linked females with thin basement membrane on electron microscopy or heterozygous carriers of COL4A3 or COL4A4 mutations), can potentially progress to proteinuria and to end-stage renal disease. Recent pedigree analyses provided evidence for digenic inheritance of Alport syndrome by concomitant mutations in COL4A3/COL4A4 or COL4A4/COL4A5. We describe a Caucasian family with concomitant COL4A3 and COL4A5 mutations, consisting of a novel c.4484A>G COL4A3 (p.Gln1495Arg) mutation and a previously reported c.1871G>A COL4A5 (p.Gly624Asp) mutation. Our segregation analysis raises the possibility that Alport syndrome resembles also digenic inheritance by COL4A3/COL4A5.

BackgroundThe myogenic response is an inherent vasoconstrictive property of resistance arteries to keep blood flow constant in response to increases in intravascular pressure. Angiotensin II (Ang II) type 1 receptors (AT1R) are broadly distributed, mechanoactivated receptors, which have been proposed to transduce myogenic vasoconstriction. However, the AT1R subtype(s) involved and their downstream G protein- and β-arrestin-mediated signaling pathways are still elusive.ObjectiveTo characterize the function of AT1aR and AT1bR in the regulation of the myogenic response of resistance size arteries and possible downstream signaling cascades mediated by Gq/11and/or β-arrestins.MethodsWe usedAgtr1a-/-,Agtr1b-/-and tamoxifen-inducible smooth muscle-specific AT1aR knockout mice (SM-Agtr1amice). FR900359, [Sar1, Ile4, Ile8] Ang II (SII) and TRV120055 were used as selective Gq/11protein inhibitor and biased agonists to activate non-canonical β-arrestin and canonical Gq/11signaling of the AT1R, respectively.ResultsMyogenic and Ang II-induced vasoconstrictions were diminished in the perfused renal vasculature ofAgtr1a-/-andSM-Agtr1amice. Similar results were observed in isolated pressurized mesenteric and cerebral arteries. Myogenic tone and Ang II-induced vasoconstrictions were normal in arteries fromAgtr1b-/-mice. The Gq/11blocker FR900359 decreased myogenic tone and Ang II vasoconstrictions while selective biased targeting of AT1R β-arrestin signaling pathways had no effects.ConclusionThe present study demonstrates that myogenic arterial constriction requires Gq/11-dependent signaling pathways of mechanoactivated AT1aR but not G protein-independent, noncanonical alternative signaling pathways in the murine mesenteric, cerebral and renal circulation.

Mutations in the ROMK1 potassium channel gene (KCNJ1) cause antenatal/neonatal Bartter syndrome type II (aBS II), a renal disorder that begins in utero, accounting for the polyhydramnios and premature delivery that is typical in affected infants, who develop massive renal salt wasting, hypokalaemic metabolic alkalosis, secondary hyperreninaemic hyperaldosteronism, hypercalciuria and nephrocalcinosis. This BS type is believed to represent a disorder of the infancy, but not in adulthood. We herein describe a female patient with a remarkably late-onset and mild clinical manifestation of BS II with compound heterozygous KCNJ1 missense mutations, consisting of a novel c.197T > A (p.I66N) and a previously reported c.875G > A (p.R292Q) KCNJ1 mutation. We implemented and evaluated the performance of two different bioinformatics-based approaches of targeted massively parallel sequencing [next generation sequencing (NGS)] in defining the molecular diagnosis. Our results demonstrate that aBS II may be suspected in patients with a late-onset phenotype. Our experimental approach of NGS-based mutation screening combined with Sanger sequencing proved to be a reliable molecular approach for defining the clinical diagnosis in our patient, and results in important differential diagnostic and therapeutic implications for patients with BS. Our results could have a significant impact on the diagnosis and methodological approaches of genetic testing in other patients with clinical unclassified phenotypes of nephrocalcinosis and congenital renal electrolyte abnormalities.

Hypertension is the greatest driver of cardiovascular disease, the most common cause of death. Finding novel model mechanisms for blood-pressure (BP) regulation is an important goal. Autosomal-dominant hypertension with brachydactyly (HTNB) clinically resembles salt-resistant essential hypertension and causes death by stroke, commonly before age 50 years. We identified mutated phosphodiesterase 3A as responsible earlier; however, definitive mechanistic proof and animal models were lacking. We now describe new kindreds, one substituted within the earlier-described regulatory region (G449S), and another with a mutation causing an amino acid substitution within the PDE3A enzymatic pocket (R864C). Both exhibit the HTNB phenotype. Mutant PDE3A (T445N) overexpression in mouse vascular smooth muscle cells causes hypertension (mean telemetry BP 130/88 mm Hg vs littermate control 115/84 mm Hg, p

BACKGROUND: Hypertension is the major risk factor for cardiovascular disease, the most common cause of death worldwide. Resistance arteries are capable of adapting their diameter independently in response to pressure and flow-associated shear stress. Ryanodine receptors (RyRs) are major Ca(2+)-release channels in the sarcoplasmic reticulum membrane of myocytes that contribute to the regulation of contractility. Vascular smooth muscle cells exhibit 3 different RyR isoforms (RyR1, RyR2, and RyR3), but the impact of individual RyR isoforms on adaptive vascular responses is largely unknown. Herein, we generated tamoxifen-inducible smooth muscle cell-specific RyR2-deficient mice and tested the hypothesis that vascular smooth muscle cell RyR2s play a specific role in elementary Ca(2+) signaling and adaptive vascular responses to vascular pressure and/or flow. METHODS AND RESULTS: Targeted deletion of the Ryr2 gene resulted in a complete loss of sarcoplasmic reticulum-mediated Ca(2+)-release events and associated Ca(2+)-activated, large-conductance K(+) channel currents in peripheral arteries, leading to increased myogenic tone and systemic blood pressure. In the absence of RyR2, the pulmonary artery pressure response to sustained hypoxia was enhanced, but flow-dependent effects, including blood flow recovery in ischemic hind limbs, were unaffected. CONCLUSIONS: Our results establish that RyR2-mediated Ca(2+)-release events in VSCM s specifically regulate myogenic tone (systemic circulation) and arterial adaptation in response to changes in pressure (hypoxic lung model), but not flow. They further suggest that vascular smooth muscle cell-expressed RyR2 deserves scrutiny as a therapeutic target for the treatment of vascular responses in hypertension and chronic vascular diseases.

Rationale : Vascular wall stretch is the major stimulus for the myogenic response of small arteries to pressure. The molecular mechanisms are elusive, but recent findings suggest that G protein–coupled receptors can elicit a stretch response. Objective : To determine whether angiotensin II type 1 receptors (AT 1 R) in vascular smooth muscle cells exert mechanosensitivity and identify the downstream ion channel mediators of myogenic vasoconstriction. Methods and Results : We used mice deficient in AT 1 R signaling molecules and putative ion channel targets, namely AT 1 R, angiotensinogen, transient receptor potential channel 6 (TRPC6) channels, or several subtypes of the voltage-gated K + (K v 7) gene family (KCNQ3, 4, or 5). We identified a mechanosensing mechanism in isolated mesenteric arteries and in the renal circulation that relies on coupling of the AT 1 R subtype a to a G q/11 protein as a critical event to accomplish the myogenic response. Arterial mechanoactivation occurs after pharmacological block of AT 1 R and in the absence of angiotensinogen or TRPC6 channels. Activation of AT 1 R subtype a by osmotically induced membrane stretch suppresses an XE991-sensitive K v channel current in patch-clamped vascular smooth muscle cells, and similar concentrations of XE991 enhance mesenteric and renal myogenic tone. Although XE991-sensitive KCNQ3, 4, and 5 channels are expressed in vascular smooth muscle cells, XE991-sensitive K + current and myogenic contractions persist in arteries deficient in these channels. Conclusions : Our results provide definitive evidence that myogenic responses of mouse mesenteric and renal arteries rely on ligand-independent, mechanoactivation of AT 1 R subtype a. The AT 1 R subtype a signal relies on an ion channel distinct from TRPC6 or KCNQ3, 4, or 5 to enact vascular smooth muscle cell activation and elevated vascular resistance.

Mutations in CD2-associated protein (CD2AP) have been identified in patients with focal segmental glomerulosclerosis (FSGS); however, reports of CD2AP mutations remain scarce. We performed Sanger sequencing in a patient with steroid-resistant FSGS and identified a heterozygous CD2AP mutation (p.T374A, c.1120 A > G). Our patient displayed mild cognitive decline, a phenotypic characteristic not previously associated with CD2AP-associated FSGS. His proteinuria was remarkably reduced by treatment with cyclosporine A. Our findings expand the genetic spectrum of CD2AP-associated disorders and broaden the associated phenotype with the co-occurrence of cognitive decline. Our case shows that cyclosporin A is a treatment option for CD2AP-associated nephropathy.