Asprosin, a Fasting-Induced Glucogenic Protein Hormone.

Hepatic glucose release into the circulation is vital for brain function and survival during periods of fasting and is modulated by an array of hormones that precisely regulate plasma glucose levels. We have identified a fasting-induced protein hormone that modulates hepatic glucose release. It is the C-terminal cleavage product of profibrillin, and we name it Asprosin. Asprosin is secreted by white adipose, circulates at nanomolar levels, and is recruited to the liver, where it activates the G protein-cAMP-PKA pathway, resulting in rapid glucose release into the circulation. Humans and mice with insulin resistance show pathologically elevated plasma asprosin, and its loss of function via immunologic or genetic means has a profound glucose- and insulin-lowering effect secondary to reduced hepatic glucose release. Asprosin represents a glucogenic protein hormone, and therapeutically targeting it may be beneficial in type II diabetes and metabolic syndrome.

The annual ASHG dinner.

Five colleagues discuss the importance of peer support developed through an annual dinner at the American Society of Human Genetics meetings. This simple networking event provided critical advising and counseling on their careers and life passages as women in academic medicine.

Regulatory variants in TCF7L2 are associated with thoracic aortic aneurysm.

Thoracic aortic aneurysm (TAA) is characterized by dilation of the aortic root or ascending/descending aorta. TAA is a heritable disease that can be potentially life threatening. While 10%-20% of TAA cases are caused by rare, pathogenic variants in single genes, the origin of the majority of TAA cases remains unknown. A previous study implicated common variants in FBN1 with TAA disease risk. Here, we report a genome-wide scan of 1,351 TAA-affected individuals and 18,295 control individuals from the Cardiovascular Health Improvement Project and Michigan Genomics Initiative at the University of Michigan. We identified a genome-wide significant association with TAA for variants within the third intron of TCF7L2 following replication with meta-analysis of four additional independent cohorts. Common variants in this locus are the strongest known genetic risk factor for type 2 diabetes. Although evidence indicates the presence of different causal variants for TAA and type 2 diabetes at this locus, we observed an opposite direction of effect. The genetic association for TAA colocalizes with an aortic eQTL of TCF7L2, suggesting a functional relationship. These analyses predict an association of higher expression of TCF7L2 with TAA disease risk. In vitro, we show that upregulation of TCF7L2 is associated with BCL2 repression promoting vascular smooth muscle cell apoptosis, a key driver of TAA disease.

SAMHD1 compound heterozygous rare variants associated with moyamoya and mitral valve disease in the absence of other features of Aicardi-Goutières syndrome.

Aicardi-Goutières syndrome (AGS) is an autosomal recessive inflammatory syndrome that manifests as an early-onset encephalopathy with both neurologic and extraneurologic clinical findings. AGS has been associated with pathogenic variants in nine genes: TREX1, RNASEH2B, RNASEH2C, RNASEH2A, SAMHD1, ADAR, IFIH1, LSM11, and RNU7-1. Diagnosis is established by clinical findings (encephalopathy and acquired microcephaly, intellectual and physical impairments, dystonia, hepatosplenomegaly, sterile pyrexia, and/or chilblains), characteristic abnormalities on cranial CT (calcification of the basal ganglia and white matter) and MRI (leukodystrophic changes), or the identification of pathogenic/likely pathogenic variants in the known genes. One of the genes associated with AGS, SAMHD1, has also been associated with a spectrum of cerebrovascular diseases, including moyamoya disease (MMD). In this report, we describe a 31-year-old male referred to genetics for MMD since childhood who lacked the hallmark features of AGS patients but was found to have compound heterozygous SAMHD1 variants. He later developed mitral valve insufficiency due to recurrent chordal rupture and ultimately underwent a heart transplant at 37 years of age. Thus, these data suggest that SAMHD1 pathogenic variants can cause MMD without typical AGS symptoms and support that SAMHD1 should be assessed in MMD patients even in the absence of AGS features.

X-linked genetic associations in sporadic thoracic aortic dissection.

The male predominance in sporadic thoracic aortic aneurysm and dissection (TAD) suggests that the X chromosome contributes to TAD, but this has not been tested. We investigated whether X-linked variation-common (minor allele frequency [MAF] ≥0.01) and rare (MAF <0.01)-was associated with sporadic TAD in three cohorts of European descent (Discovery: 364 cases, 874 controls; Replication: 516 cases, 440,131 controls, and ARIC [Atherosclerosis Risk in Communities study]: 753 cases, 2247 controls). For analysis of common variants, we applied a sex-stratified logistic regression model followed by a meta-analysis of sex-specific odds ratios. Furthermore, we conducted a meta-analysis of overlapping common variants between the Discovery and Replication cohorts. For analysis of rare variants, we used a sex-stratified optimized sequence kernel association test model. Common variants results showed no statistically significant findings in the Discovery cohort. An intergenic common variant near SPANXN1 was statistically significant in the Replication cohort (p = 1.81 × 10-8). The highest signal from the meta-analysis of the Discovery and Replication cohorts was a ZNF182 intronic common variant (p = 3.5 × 10-6). In rare variants results, RTL9 reached statistical significance (p = 5.15 × 10-5). Although most of our results were statistically insignificant, our analysis is the most comprehensive X-chromosome association analysis of sporadic TAD to date.

Rare variants in ANO1, encoding a calcium-activated chloride channel, predispose to moyamoya disease.

Moyamoya disease, a cerebrovascular disease leading to strokes in children and young adults, is characterized by progressive occlusion of the distal internal carotid arteries and the formation of collateral vessels. Altered genes play a prominent role in the aetiology of moyamoya disease, but a causative gene is not identified in the majority of cases. Exome sequencing data from 151 individuals from 84 unsolved families were analysed to identify further genes for moyamoya disease, then candidate genes assessed in additional cases (150 probands). Two families had the same rare variant in ANO1, which encodes a calcium-activated chloride channel, anoctamin-1. Haplotype analyses found the families were related, and ANO1 p.Met658Val segregated with moyamoya disease in the family with an LOD score of 3.3. Six additional ANO1 rare variants were identified in moyamoya disease families. The ANO1 rare variants were assessed using patch-clamp recordings, and the majority of variants, including ANO1 p.Met658Val, displayed increased sensitivity to intracellular Ca2+. Patients harbouring these gain-of-function ANO1 variants had classic features of moyamoya disease, but also had aneurysm, stenosis and/or occlusion in the posterior circulation. Our studies support that ANO1 gain-of-function pathogenic variants predispose to moyamoya disease and are associated with unique involvement of the posterior circulation.

Correction: Integrative analysis of genomic variants reveals new associations of candidate haploinsufficient genes with congenital heart disease.

[This corrects the article DOI: 10.1371/journal.pgen.1009679.].

Integrative analysis of genomic variants reveals new associations of candidate haploinsufficient genes with congenital heart disease.

Numerous genetic studies have established a role for rare genomic variants in Congenital Heart Disease (CHD) at the copy number variation (CNV) and de novo variant (DNV) level. To identify novel haploinsufficient CHD disease genes, we performed an integrative analysis of CNVs and DNVs identified in probands with CHD including cases with sporadic thoracic aortic aneurysm. We assembled CNV data from 7,958 cases and 14,082 controls and performed a gene-wise analysis of the burden of rare genomic deletions in cases versus controls. In addition, we performed variation rate testing for DNVs identified in 2,489 parent-offspring trios. Our analysis revealed 21 genes which were significantly affected by rare CNVs and/or DNVs in probands. Fourteen of these genes have previously been associated with CHD while the remaining genes (FEZ1, MYO16, ARID1B, NALCN, WAC, KDM5B and WHSC1) have only been associated in small cases series or show new associations with CHD. In addition, a systems level analysis revealed affected protein-protein interaction networks involved in Notch signaling pathway, heart morphogenesis, DNA repair and cilia/centrosome function. Taken together, this approach highlights the importance of re-analyzing existing datasets to strengthen disease association and identify novel disease genes and pathways.

Smooth muscle α-actin missense variant promotes atherosclerosis through modulation of intracellular cholesterol in smooth muscle cells.

AIMS: The variant p.Arg149Cys in ACTA2, which encodes smooth muscle cell (SMC)-specific α-actin, predisposes to thoracic aortic disease and early onset coronary artery disease in individuals without cardiovascular risk factors. This study investigated how this variant drives increased atherosclerosis. METHODS AND RESULTS: Apoe-/- mice with and without the variant were fed a high-fat diet for 12 weeks, followed by evaluation of atherosclerotic plaque formation and single-cell transcriptomics analysis. SMCs explanted from Acta2R149C/+ and wildtype (WT) ascending aortas were used to investigate atherosclerosis-associated SMC phenotypic modulation. Hyperlipidemic Acta2R149C/+Apoe-/- mice have a 2.5-fold increase in atherosclerotic plaque burden compared to Apoe-/- mice with no differences in serum lipid levels. At the cellular level, misfolding of the R149C α-actin activates heat shock factor 1, which increases endogenous cholesterol biosynthesis and intracellular cholesterol levels through increased HMG-CoA reductase (HMG-CoAR) expression and activity. The increased cellular cholesterol in Acta2R149C/+ SMCs induces endoplasmic reticulum stress and activates PERK-ATF4-KLF4 signaling to drive atherosclerosis-associated phenotypic modulation in the absence of exogenous cholesterol, while WT cells require higher levels of exogenous cholesterol to drive phenotypic modulation. Treatment with the HMG-CoAR inhibitor pravastatin successfully reverses the increased atherosclerotic plaque burden in Acta2R149C/+Apoe-/- mice. CONCLUSION: These data establish a novel mechanism by which a pathogenic missense variant in a smooth muscle-specific contractile protein predisposes to atherosclerosis in individuals without hypercholesterolemia or other risk factors. The results emphasize the role of increased intracellular cholesterol levels in driving SMC phenotypic modulation and atherosclerotic plaque burden.

2022 ACC/AHA Guideline for the Diagnosis and Management of Aortic Disease: A Report of the American Heart Association/American College of Cardiology Joint Committee on Clinical Practice Guidelines.

AIM: The "2022 ACC/AHA Guideline for the Diagnosis and Management of Aortic Disease" provides recommendations to guide clinicians in the diagnosis, genetic evaluation and family screening, medical therapy, endovascular and surgical treatment, and long-term surveillance of patients with aortic disease across its multiple clinical presentation subsets (ie, asymptomatic, stable symptomatic, and acute aortic syndromes). METHODS: A comprehensive literature search was conducted from January 2021 to April 2021, encompassing studies, reviews, and other evidence conducted on human subjects that were published in English from PubMed, EMBASE, the Cochrane Library, CINHL Complete, and other selected databases relevant to this guideline. Additional relevant studies, published through June 2022 during the guideline writing process, were also considered by the writing committee, where appropriate. Structure: Recommendations from previously published AHA/ACC guidelines on thoracic aortic disease, peripheral artery disease, and bicuspid aortic valve disease have been updated with new evidence to guide clinicians. In addition, new recommendations addressing comprehensive care for patients with aortic disease have been developed. There is added emphasis on the role of shared decision making, especially in the management of patients with aortic disease both before and during pregnancy. The is also an increased emphasis on the importance of institutional interventional volume and multidisciplinary aortic team expertise in the care of patients with aortic disease.

An FBN1 deep intronic variant is associated with pseudoexon formation and a variable Marfan phenotype in a five generation family.

Exome sequencing of genes associated with heritable thoracic aortic disease (HTAD) failed to identify a pathogenic variant in a large family with Marfan syndrome (MFS). A genome-wide linkage analysis for thoracic aortic disease identified a peak at 15q21.1, and genome sequencing identified a novel deep intronic FBN1 variant that segregated with thoracic aortic disease in the family (LOD score 2.7) and was predicted to alter splicing. RT-PCR and bulk RNA sequencing of RNA harvested from fibroblasts explanted from the affected proband revealed an insertion of a pseudoexon between exons 13 and 14 of the FBN1 transcript, predicted to lead to nonsense mediated decay (NMD). Treating the fibroblasts with an NMD inhibitor, cycloheximide, greatly improved the detection of the pseudoexon-containing transcript. Family members with the FBN1 variant had later onset aortic events and fewer MFS systemic features than typical for individuals with haploinsufficiency of FBN1. Variable penetrance of the phenotype and negative genetic testing in MFS families should raise the possibility of deep intronic FBN1 variants and the need for additional molecular studies.

Preventing Cholesterol-Induced Perk (Protein Kinase RNA-Like Endoplasmic Reticulum Kinase) Signaling in Smooth Muscle Cells Blocks Atherosclerotic Plaque Formation.

BACKGROUND: Vascular smooth muscle cells (SMCs) undergo complex phenotypic modulation with atherosclerotic plaque formation in hyperlipidemic mice, which is characterized by de-differentiation and heterogeneous increases in the expression of macrophage, fibroblast, osteogenic, and stem cell markers. An increase of cellular cholesterol in SMCs triggers similar phenotypic changes in vitro with exposure to free cholesterol due to cholesterol entering the endoplasmic reticulum, triggering endoplasmic reticulum stress and activating Perk (protein kinase RNA-like endoplasmic reticulum kinase) signaling. METHODS: We generated an SMC-specific Perk knockout mouse model, induced hyperlipidemia in the mice by AAV-PCSK9DY injection, and subjected them to a high-fat diet. We then assessed atherosclerotic plaque formation and performed single-cell transcriptomic studies using aortic tissue from these mice. RESULTS: SMC-specific deletion of Perk reduces atherosclerotic plaque formation in male hyperlipidemic mice by 80%. Single-cell transcriptomic data identify 2 clusters of modulated SMCs in hyperlipidemic mice, one of which is absent when Perk is deleted in SMCs. The 2 modulated SMC clusters have significant overlap of transcriptional changes, but the Perk-dependent cluster uniquely shows a global decrease in the number of transcripts. SMC-specific Perk deletion also prevents migration of both contractile and modulated SMCs from the medial layer of the aorta. CONCLUSIONS: Our results indicate that hypercholesterolemia drives both Perk-dependent and Perk-independent SMC modulation and that deficiency of Perk significantly blocks atherosclerotic plaque formation.

Smooth Muscle-Alpha Actin R149C Pathogenic Variant Downregulates Integrin Recruitment at Cell-Matrix Adhesions and Decreases Cellular Contractility.

Thoracic aortic aneurysm is found in patients with ACTA2 pathogenic variants. ACTA2 missense variants are associated with impaired aortic smooth muscle cell (SMC) contraction. This study tested the hypothesis that the Acta2R149C/+ variant alters actin isoform expression and decreases integrin recruitment, thus, reducing aortic contractility. Stress relaxation measurements in thoracic aortic rings showed two functional regimes with a reduction of stress relaxation in the aorta from Acta2R149C/+ mice at low tension, but not at high tension values. Contractile responses to phenylephrine and potassium chloride were 50% lower in Acta2R149C/+ mice than in wild-type (WT) mice. Additionally, SMC were immunofluorescently labeled for specific proteins and imaged by confocal or total internal reflection fluorescence microscopy. The quantification of protein fluorescence of Acta2R149C/+ SMC showed a downregulation in smooth muscle α-actin (SMα-actin) and a compensatory upregulation of smooth muscle γ-actin (SMγ-actin) compared to WT cells. These results suggest that downregulation of SMα-actin leads to reduced SMC contractility, while upregulation of SMγ-actin may lead to increased SMC stiffness. Decreased α5ß1 and α2ß1 integrin recruitment at cell-matrix adhesions further reduce the ability of mutant cells to participate in cell-matrix crosstalk. Collectively, the results suggest that mutant Acta2R149C/+ aortic SMC have reduced contractility and interaction with the matrix, which are potential long-term contributing factors to thoracic aortic aneurysms.

Resistance of Acta2R149C/+ mice to aortic disease is associated with defective release of mutant smooth muscle α-actin from the chaperonin-containing TCP1 folding complex.

Pathogenic variants of the gene for smooth muscle α-actin (ACTA2), which encodes smooth muscle (SM) α-actin, predispose to heritable thoracic aortic disease. The ACTA2 variant p.Arg149Cys (R149C) is the most common alteration; however, only 60% of carriers have a dissection or undergo repair of an aneurysm by 70 years of age. A mouse model of ACTA2 p.Arg149Cys was generated using CRISPR/Cas9 technology to determine the etiology of reduced penetrance. Acta2R149C/+ mice had significantly decreased aortic contraction compared with WT mice but did not form aortic aneurysms or dissections when followed to 24 months, even when hypertension was induced. In vitro motility assays found decreased interaction of mutant SM α-actin filaments with SM myosin. Polymerization studies using total internal reflection fluorescence microscopy showed enhanced nucleation of mutant SM α-actin by formin, which correlated with disorganized and reduced SM α-actin filaments in Acta2R149C/+ smooth muscle cells (SMCs). However, the most prominent molecular defect was the increased retention of mutant SM α-actin in the chaperonin-containing t-complex polypeptide folding complex, which was associated with reduced levels of mutant compared with WT SM α-actin in Acta2R149C/+ SMCs. These data indicate that Acta2R149C/+ mice do not develop thoracic aortic disease despite decreased contraction of aortic segments and disrupted SM α-actin filament formation and function in Acta2R149C/+ SMCs. Enhanced binding of mutant SM α-actin to chaperonin-containing t-complex polypeptide decreases the mutant actin versus WT monomer levels in Acta2R149C/+ SMCs, thus minimizing the effect of the mutation on SMC function and potentially preventing aortic disease in the Acta2R149C/+ mice.

Evaluating perinatal and neonatal outcomes among children with vascular Ehlers-Danlos syndrome.

PURPOSE: Birth outcomes data for patients with vascular Ehlers-Danlos syndrome (VEDS) are limited. METHODS: Patients with a pathogenic or likely pathogenic COL3A1 variant were included. Outcomes included gestational age (GA), birthweight (BW), and maternal complications. Birth outcomes were first compared with that of US population data, then compared by sex, maternal affected status, and COL3A1 genotype. RESULTS: A total of 41 children were included (70.7% male), including 32 with high-risk (missense and splice site) variants. Preterm birth (<37 weeks) was more common in patients with VEDS than in the US population (48.8% vs 12.2%, P < .0001). Low BW (<2.5 kg) was also more common in patients with VEDS than in the US population (P < .0001), although, it was appropriate after GA adjustment (median GA-adjusted z-score 0.01 vs z-score 0.0, P = .26). No differences in GA or BW were observed by sex or maternal affected status. Those with high-risk variants were more likely to be born preterm than those with haploinsufficient variants, although this did not meet significance criteria (53% vs 33%, P = .35). Of the 6 affected mothers, 5 had perinatal complications. CONCLUSION: Preterm birth is more common in children with VEDS than in the general population. Maternal affected status is not associated with preterm birth, suggesting that risk is conferred by the fetal VEDS diagnosis alone.

Aortic root dilatation and dilated cardiomyopathy in an adult with Tatton-Brown-Rahman syndrome.

Tatton-Brown-Rahman syndrome is an autosomal dominant overgrowth syndrome caused by pathogenic DNMT3A variants in the germline. Clinical findings of tall stature due to postnatal overgrowth, intellectual disability, and characteristic facial features, are the most consistent findings observed in patients with Tatton-Brown-Rahman syndrome (TBRS). Since the syndrome was first described in 2014, an expanding spectrum of neuropsychiatric, musculoskeletal, neurological, and cardiovascular manifestations have been reported. However, most TBRS cases described in the literature are children with de novo DNMT3A variants, signaling a need to better characterize the phenotypes in adults. In this report, we describe a 34 year old referred to genetics for possible Marfan syndrome with aortic root dilatation, mitral valve prolapse, and dilated cardiomyopathy, who was diagnosed with TBRS due to a heterozygous de novo DNMT3A variant. This represents the third reported TBRS case with aortic root dilation and the second with cardiomyopathy. Collectively, these data provide evidence for an association with aortic disease and cardiomyopathy, highlight the clinical overlap with Marfan syndrome, and suggest that cardiovascular surveillance into adulthood is indicated.

Expanding ACTA2 genotypes with corresponding phenotypes overlapping with smooth muscle dysfunction syndrome.

Pathogenic variants in ACTA2, encoding smooth muscle α-actin, predispose to thoracic aortic aneurysms and dissections. ACTA2 variants altering arginine 179 predispose to a more severe, multisystemic disease termed smooth muscle dysfunction syndrome (SMDS; OMIM 613834). Vascular complications of SMDS include patent ductus arteriosus (PDA) or aortopulmonary window, early-onset thoracic aortic disease (TAD), moyamoya-like cerebrovascular disease, and primary pulmonary hypertension. Patients also have dysfunction of other smooth muscle-dependent systems, including congenital mydriasis, hypotonic bladder, and gut hypoperistalsis. Here, we describe five patients with novel heterozygous ACTA2 missense variants, p.Arg179Gly, p.Met46Arg, p.Thr204Ile, p.Arg39Cys, and p.Ile66Asn, who have clinical complications that align or overlap with SMDS. Patients with the ACTA2 p.Arg179Gly and p.Thr204Ile variants display classic features of SMDS. The patient with the ACTA2 p.Met46Arg variant exhibits exclusively vascular complications of SMDS, including early-onset TAD, PDA, and moyamoya-like cerebrovascular disease. The patient with the ACTA2 p.Ile66Asn variant has an unusual vascular complication, a large fusiform internal carotid artery aneurysm. The patient with the ACTA2 p.Arg39Cys variant has pulmonary, gastrointestinal, and genitourinary complications of SMDS but no vascular manifestations. Identifying pathogenic ACTA2 variants associated with features of SMDS is critical for aggressive surveillance and management of vascular and nonvascular complications and delineating the molecular pathogenesis of SMDS.

Spontaneous coronary artery dissection is infrequent in individuals with heritable thoracic aortic disease despite partially shared genetic susceptibility.

Spontaneous coronary artery dissection (SCAD) is a potential precipitant of myocardial infarction and sudden death for which the etiology is poorly understood. Mendelian vascular and connective tissue disorders underlying thoracic aortic disease (TAD), have been reported in ~5% of individuals with SCAD. We therefore hypothesized that patients with TAD are at elevated risk for SCAD. We queried registries enrolling patients with TAD to define the incidence of SCAD. Of 7568 individuals enrolled, 11 (0.15%) were found to have SCAD. Of the sequenced cases (9/11), pathogenic variants were identified (N = 9), including COL3A1 (N = 3), FBN1 (N = 2), TGFBR2 (N = 2), TGFBR1 (N = 1), and PRKG1 (N = 1). Individuals with SCAD had an increased frequency of iliac artery dissection (25.0% vs. 5.1%, p = 0.047). The prevalence of SCAD among individuals with TAD is low. The identification of pathogenic variants in genes previously described in individuals with SCAD, particularly those underlying vascular Ehlers-Danlos, Marfan syndrome, and Loeys-Dietz syndrome, is consistent with prior reports from clinical SCAD series. Further research is needed to identify specific genetic influences on SCAD risk.

Cholesterol-Induced Phenotypic Modulation of Smooth Muscle Cells to Macrophage/Fibroblast-like Cells Is Driven by an Unfolded Protein Response.

OBJECTIVE: Vascular smooth muscle cells (SMCs) dedifferentiate and initiate expression of macrophage markers with cholesterol exposure. This phenotypic switching is dependent on the transcription factor Klf4 (Krüppel-like factor 4). We investigated the molecular pathway by which cholesterol induces SMC phenotypic switching. Approach and Results: With exposure to free cholesterol, SMCs decrease expression of contractile markers, activate Klf4, and upregulate a subset of macrophage and fibroblast markers characteristic of modulated SMCs that appear with atherosclerotic plaque formation. These phenotypic changes are associated with activation of all 3 pathways of the endoplasmic reticulum unfolded protein response (UPR), Perk (protein kinase RNA-like endoplasmic reticulum kinase), Ire (inositol-requiring enzyme) 1α, and Atf (activating transcription factor) 6. Blocking the movement of cholesterol from the plasma membrane to the endoplasmic reticulum prevents free cholesterol-induced UPR, Klf4 activation, and upregulation of the majority of macrophage and fibroblast markers. Cholesterol-induced phenotypic switching is also prevented by global UPR inhibition or specific inhibition of Perk signaling. Exposure to chemical UPR inducers, tunicamycin and thapsigargin, is sufficient to induce these same phenotypic transitions. Finally, analysis of published single-cell RNA sequencing data during atherosclerotic plaque formation in hyperlipidemic mice provides preliminary in vivo evidence of a role of UPR activation in modulated SMCs. CONCLUSIONS: Our data demonstrate that UPR is necessary and sufficient to drive phenotypic switching of SMCs to cells that resemble modulated SMCs found in atherosclerotic plaques. Preventing a UPR in hyperlipidemic mice diminishes atherosclerotic burden, and our data suggest that preventing SMC transition to dedifferentiated cells expressing macrophage and fibroblast markers contributes to this decreased plaque burden.

The Secrets of the Frogs Heart.

The heart of the African clawed frog has a double-inlet and single-outlet ventricle supporting systemic and pulmonary circulations via a truncus, and a lifespan of 25-30 years. We sought to understand the unique cardiac anatomic and physiologic characteristics, with balanced circulation and low metabolic rate, by comparing the basic anatomy structures with focused echocardiography and cardiac magnetic resonance imaging. Twenty-four adult female African clawed frogs were randomly subjected to anatomic dissection (n = 4), echocardiography (n = 10), and cardiac magnetic resonance (n = 10). All anatomical features were confirmed and compared with echocardiography and cardiac magnetic resonance imaging. The main characteristics of the cardiovascular circulation in frogs are the following: Intact interatrial septum, with two separate atrio-ventricular valves, preventing atrial mixing of oxygenated and desaturated blood. Single spongiform ventricular cavity, non-conducive for homogeneous mixing. Single outlet with a valve-like mobile spiral structure, actively streaming into systemic and pulmonary arteries. Intact interatrial septum, spongiform ventricle, and valve-like spiral in the conus arteriosus are likely responsible for balanced systemic and pulmonary circulation in frogs, in spite of double-inlet and single-outlet ventricle.