Quantitative trait and transcriptome analysis of genetic complexity underpinning cardiac interatrial septation in mice using an advanced intercross line.

Unlike single-gene mutations leading to Mendelian conditions, common human diseases are likely to be emergent phenomena arising from multilayer, multiscale, and highly interconnected interactions. Atrial and ventricular septal defects are the most common forms of cardiac congenital anomalies in humans. Atrial septal defects (ASD) show an open communication between the left and right atria postnatally, potentially resulting in serious hemodynamic consequences if untreated. A milder form of atrial septal defect, patent foramen ovale (PFO), exists in about one-quarter of the human population, strongly associated with ischaemic stroke and migraine. The anatomic liabilities and genetic and molecular basis of atrial septal defects remain unclear. Here, we advance our previous analysis of atrial septal variation through quantitative trait locus (QTL) mapping of an advanced intercross line (AIL) established between the inbred QSi5 and 129T2/SvEms mouse strains, that show extremes of septal phenotypes. Analysis resolved 37 unique septal QTL with high overlap between QTL for distinct septal traits and PFO as a binary trait. Whole genome sequencing of parental strains and filtering identified predicted functional variants, including in known human congenital heart disease genes. Transcriptome analysis of developing septa revealed downregulation of networks involving ribosome, nucleosome, mitochondrial, and extracellular matrix biosynthesis in the 129T2/SvEms strain, potentially reflecting an essential role for growth and cellular maturation in septal development. Analysis of variant architecture across different gene features, including enhancers and promoters, provided evidence for the involvement of non-coding as well as protein-coding variants. Our study provides the first high-resolution picture of genetic complexity and network liability underlying common congenital heart disease, with relevance to human ASD and PFO.

Stroke in Young Military Men With Heterozygous for MTHFR Gene Mutation or Factor V Leiden Gene Mutation Associated With Patent Foramen Ovale: Report of Two Cases and Therapeutic Strategy.

We report two cases of Brazilian patients (a 22-year-old male and a 48-year-old male) with ischemic stroke, whose arterial vascular study and echocardiographic investigation did not reveal any steno-occlusive arterial disease or typical cardioembolic finding, such as atrial fibrillation or myocardial dysfunction. A transcranial Doppler ultrasound and a transesophageal echocardiogram showed a patent foramen ovale (PFO), and the laboratory screening for coagulation abnormalities showed heterozygosity for MTHFR C677T and A1298C in one of the patients and heterozygosity for factor V Leiden gene mutations in the other patient. The significance of the association of PFO with Methylenetetrahydrofolate (MTHFR) C677T and A1298C variants or factor V Leiden mutation is discussed as a possible cause of ischemic stroke through paradoxical embolism from a venous source. There is a high prevalence of these two mentioned conditions in the general population, so we discuss two cases in which indication for anticoagulant therapy or percutaneous closure of PFO prevails.

The Genetic Landscape of Patent Foramen Ovale: A Systematic Review.

Patent Foramen Ovale (PFO) is a common postnatal defect of cardiac atrial septation. A certain degree of familial aggregation has been reported. Animal studies suggest the involvement of the Notch pathway and other cardiac transcription factors (GATA4, TBX20, NKX2-5) in Foramen Ovale closure. This review evaluates the contribution of genetic alterations in PFO development. We systematically reviewed studies that assessed rare and common variants in subjects with PFO. The protocol was registered with PROSPERO and followed MOOSE guidelines. We systematically searched English studies reporting rates of variants in PFO subjects until the 30th of June 2021. Among 1231 studies, we included four studies: two of them assessed the NKX2-5 gene, the remaining reported variants of chromosome 4q25 and the GATA4 S377G variant, respectively. We did not find any variant associated with PFO, except for the rs2200733 variant of chromosome 4q25 in atrial fibrillation patients. Despite the scarceness of evidence so far, animal studies and other studies that did not fulfil the criteria to be included in the review indicate a robust genetic background in PFO. More research is needed on the genetic determinants of PFO.

Foramen ovale closure is a process of endothelial-to-mesenchymal transition leading to fibrosis.

Patent foramen ovale (PFO) is an atrial septal deformity present in around 25% of the general population. PFO is associated with major causes of morbidity, including stroke and migraine. PFO appears to be heritable but genes involved in the closure of foramen ovale have not been identified. The aim of this study is to determine molecular pathways and genes that are responsible to the postnatal closure of the foramen ovale. Using Sprague-Dawley rat hearts as a model we analysed the dynamic histological changes and gene expressions at the foramen ovale region between embryonic day 20 and postnatal day 7. We observed a gradual loss of the endothelial marker PECAM1, an upregulation of the mesenchymal marker vimentin and α-smooth muscle actin, the elevation of the transcription factor Snail, and an increase of fibroblast activation protein (FAP) in the foramen ovale region as well as the deposition of collagen-rich connective tissues at the closed foramen ovale, suggesting endothelial-to-mesenchymal transition (EndMT) occurring during foramen ovale closure which leads to fibrosis. In addition, Notch1 and Notch3 receptors, Notch ligand Jagged1 and Notch effector HRT1 were highly expressed in the endocardium of the foramen ovale region during EndMT. Activation of Notch3 alone in an endothelial cell culture model was able to drive EndMT and transform endothelial cells to mesenchymal phenotype. Our data demonstrate for the first time that FO closure is a process of EndMT-mediated fibrosis, and Notch signalling is an important player participating in this process. Elucidation of the molecular mechanisms of the closure of foramen ovale informs the pathogenesis of PFO and may provide potential options for screening and prevention of PFO related conditions.

Ischemic stroke and patent foramen ovale: risk factors and genetic profile.

BACKGROUND: Patent foramen ovale (PFO) is considered to be a risk factor for ischemic cerebrovascular disease (ICVD), especially in young people. However, the potential pathophysiological relevance in ischemic stroke is controversial and in need of further investigation. In this study, we examined the conventional risk factors and the distribution of 100 polymorphisms in 47 suspected susceptibility genes for ICVD in stroke patients with or without a PFO. METHODS: In the South Stockholm Ischemic Stroke Study, 928 ICVD patients and 602 controls were genotyped for 100 different gene polymorphisms. The stroke patients also underwent relevant investigation and standardized blood tests. Patients who underwent transeosophageal echocardiography as part of their investigation were divided into groups that either had or did not have a PFO. RESULTS: There were no significant differences in the 2 groups with regard to conventional risk factors or blood analyses. Three different polymorphisms located in the prothrombin, F2 (20210G/A), and apolipoprotein-C3 (-641A/C and -455T/A) genes were significantly associated with ICVD and PFO. The strongest association was found for F2 (P = .0049; odds ratio 26.4). CONCLUSIONS: We found that F2, which previously has been described as being a possible link between PFO and ICVD, was significantly associated with ICVD and PFO. There was also a trend toward an association between 2 other polymorphisms in the APO-CIII gene and PFO and ICVD.

G1691A factor V and G20210A FII mutations, acute ischemic stroke of unknown cause, and patent foramen ovale.

BACKGROUND: Genetic polymorphisms of haemostatic factors such as G1691A factor V (FV Leiden) and G20210A prothrombin (FII) may be involved in the onset of patent foramen ovale (PFO)-related cerebral ischaemia. We assessed the possible association between such inherited thrombophilic alterations and right-to-left shunt in patients with stroke. METHODS: We investigated the presence of G20210A FII and FV Leiden mutations in 340 Caucasian patients consecutively evaluated by our Angiology Unit for stroke of unknown cause. PFO was assessed in all patients with Transcranial Doppler with intravenous injection of agitated saline. Stroke patients were divided into two groups: patients with PFO (n=136), and patients without PFO (n=204). As control group, we studied 272 subjects with early venous insufficiency. RESULTS: The prevalence of FII G20210A mutation was significantly higher in patients with PFO vs. controls (OR: 2.90; 95% CI: 1.19-7.07) and in patients without PFO vs. controls (OR: 2.88; 95% CI: 1.25-6.60) but was similar in patients with and without PFO (OR: 1.11; 95% CI: 0.51-2.44). The frequency of FV Leiden mutation was similar in the three groups. Across the population the presence of the FII G20210A mutation (OR: 2.97;95% CI: 1.32-6.69), a history of DVT (OR: 1.04; 95% CI: 1.02-1.06), and oestrogen-containing contraceptive therapy (OR: 1.14; 95% CI: 1.09-1.18) were all associated with stroke of unknown cause after adjustment for other risk factors, This was not the case with PFO. CONCLUSIONS: Our data do not support the assumption that these inherited thrombophilic alterations are associated with PFO in patients with cryptogenic stroke. FII G20210A mutation may be associated with cryptogenic stroke irrespective of the presence of PFO.

QTL mapping of complex binary traits in an advanced intercross line.

An advanced intercross line (AIL) is an easier and more cost-effective approach compared to recombinant inbred lines for fine mapping of quantitative trait loci (QTL) identified by F(2) designs. In an AIL, a complex binary trait can be mapped through analysis of either continuously distributed proxy traits for the liability of the binary trait or the liability itself, the latter presenting the greater statistical challenge. In another work, we successfully applied both approaches in an AIL to fine map previously identified QTL underlying anatomical parameters of the cardiac inter-atrial septum including patent foramen ovale. Here, we describe the statistical methods that we used to analyse complex binary traits in our AIL design. This is achieved using a likelihood-based method, with the expectation-maximisation algorithm allowing use of standard logistic regression methods for model fitting.

Progressive anatomical closure of foramen ovale in normal neonatal mouse hearts.

In the prenatal heart, right-to-left atrial shunting of blood through the foramen ovale is essential for proper circulation. After birth, as the pulmonary circulation is established, the foramen ovale functionally closes as a result of changes in the relative pressure of the two atrial chambers, ensuring the separation of oxygen depleted venous blood in the right atrium from the oxygenated blood entering the left atrium. Little is known regarding the process of anatomical closure of the foramen ovale in the postnatal heart. Genetically engineered mouse models are powerful tools to study heart development and to reveal mechanisms underlying cardiac anomalies, including defects in atrioventricular septation. Using three-dimensional reconstructions of serial sectioned hearts at early postnatal Days 2-7, we show a progressive reduction in the size of the interatrial communication throughout this period and complete closure by postnatal Day 7. Furthermore we demonstrate that fusion of the septum primum and septum secundum occurs between 4 weeks and 3 months of age. This study provides a standard timeline for morphological closure of the right-left atrial communication and fusion between the atrial septa in normal mouse hearts.

Investigation of association between PFO complicated by cryptogenic stroke and a common variant of the cardiac transcription factor GATA4.

Patent foramen ovale (PFO) is associated with clinical conditions including cryptogenic stroke, migraine and varicose veins. Data from studies in humans and mouse suggest that PFO and the secundum form of atrial septal defect (ASDII) exist in an anatomical continuum of septal dysmorphogenesis with a common genetic basis. Mutations in multiple members of the evolutionarily conserved cardiac transcription factor network, including GATA4, cause or predispose to ASDII and PFO. Here, we assessed whether the most prevalent variant of the GATA4 gene, S377G, was significantly associated with PFO or ASD. Our analysis of world indigenous populations showed that GATA4 S377G was largely Caucasian-specific, and so subjects were restricted to those of Caucasian descent. To select for patients with larger PFO, we limited our analysis to those with cryptogenic stroke in which PFO was a subsequent finding. In an initial study of Australian subjects, we observed a weak association between GATA4 S377G and PFO/Stroke relative to Caucasian controls in whom ASD and PFO had been excluded (OR = 2.16; p = 0.02). However, in a follow up study of German Caucasians no association was found with either PFO or ASD. Analysis of combined Australian and German data confirmed the lack of a significant association. Thus, the common GATA4 variant S377G is likely to be relatively benign in terms of its participation in CHD and PFO/Stroke.

Two concurrent chromosomal aberrations involving interstitial deletion in 1q24.2q25.2 and inverted duplication and deletion in 10q26 in a patient with stroke associated with antithrombin deficiency and a patent foramen ovale.

Advanced high-throughput molecular cytogenetic analysis has enabled the identification of small chromosomal rearrangements, and two or more concurrently occurring chromosomal rearrangements have been identified using this technique. A girl with severe psychomotor developmental delay associated with an uncertain abnormality (detected by conventional karyotyping) in chromosome 10q had a sudden stroke at the age of 35 months. Laboratory and radiographic examinations revealed antithrombin (AT) deficiency and a patent foramen ovale (PFO). Two concurrent chromosomal aberrations, inverted duplication and deletion in the 10q26 region and a microdeletion in the 1q24.2q25.2 region including the AT gene (SERPINC1), were identified by microarray-based comparative genomic hybridization analysis. Both chromosomal aberrations were found to be of paternal origin. This study described the concurrence of chromosomal rearrangements involving two chromosomes, and estimated the frequency of two or more chromosomal aberrations as 2-4%.

A gain-of-function TBX20 mutation causes congenital atrial septal defects, patent foramen ovale and cardiac valve defects.

BACKGROUND: Ostium secundum atrial septal defects (ASDII) account for approximately 10% of all congenital heart defects (CHD), and mutations in cardiac transcription factors, including TBX20, were identified as an underlying cause for ASDII. However, very little is known about disease penetrance in families and functional consequences of inherited TBX20 mutations. METHODS: The coding region of TBX20 was directly sequenced in 170 ASDII patients. Functional consequences of one novel mutation were investigated by surface plasmon resonance, CD spectropolarymetry, fluorescence spectrophotometry, luciferase assay and chromatin immunoprecipitation. RESULTS: We found a novel mutation in a highly conserved residue in the T-box DNA binding domain (I121M) segregating with CHD in a three generation kindred. Four mutation carriers revealed cardiac phenotypes in terms of cribriform ASDII, large patent foramen ovale or cardiac valve defects. Interestingly, tertiary hydrophobic interactions within the mutant TBX20 T-box were significantly altered leading to a more dynamic structure of the protein. Moreover, Tbx20-I121M resulted in a significantly enhanced transcriptional activity, which was further increased in the presence of co-transcription factors GATA4/5 and NKX2-5. Occupancy of DNA binding sites on target genes was also increased. CONCLUSIONS: We suggest that TBX20-I121M adopts a more fluid tertiary structure leading to enhanced interactions with cofactors and more stable transcriptional complexes on target DNA sequences. Our data, combined with that of others, suggest that human ASDII may be related to loss-of-function as well as gain-of-function TBX20 mutations.

Population-based assessment of familial inheritance and neurologic comorbidities among patients with an isolated atrial septal defect.

BACKGROUND: Interatrial shunts, caused by either atrial septal defect (ASD) or patent foramen ovale, have been reported to have a familial association. We sought to examine the familial risk of isolated interatrial shunt and explore associated comorbidities of stroke, transient ischemic attack (TIA), and migraine using a population database. METHODS: The Utah Population Database is linked to inpatient and outpatient records from the University of Utah Health Science Center. Patients with an interatrial shunt were identified, and those with any other form of congenital heart disease or an inheritable syndrome associated with ASD were excluded. Of the 9452 individuals diagnosed with isolated interatrial shunt, 6179 (65%) had sufficient familial and follow-up data for analysis. Five age/gender matched controls were randomly selected per case. Cases and their relatives were compared with controls to assess the relative risk for each comorbid condition. RESULTS: Relatives of interatrial shunt cases had an increased risk for interatrial shunt: siblings relative risk (RR) 6.98 (95% confidence interval [CI] 5.75-8.48; P < 1.0 x 10(-16)), first-degree RR 5.64 (95% CI 4.76-6.68; P < 1.0 x 10(-16)), and second-degree RR 1.75 (95% CI 1.32-2.32; P= 0.0001). Patients with interatrial shunt were more likely to have a comorbid condition compared with controls (RR 21.3, 95% CI 17.1-26.5; P < 1.0 x 10(-16)). First-degree relatives of cases had an increased risk of TIA (RR 1.70, 95% CI 1.18-2.45; P= 0.0045), but no increase risk of stroke or migraine compared with controls. CONCLUSIONS: There is a strong familial inheritance pattern for isolated interatrial shunt, with significantly higher risk of interatrial shunt among affected patients' siblings, first-, and second-degree relatives. Relatives of affected individuals also had a higher risk of TIA, a trend toward an increased risk for stroke, but no increased risk of migraine headache.

[Patent foramen ovale: "les liaisons dangereuses" between anatomy and genetics]. / Forame ovale pervio: le relazioni pericolose fra anatomia e genetica.

We reported a case of two 24-year-old and 17-year-old male patients with episode of transient ischemic attacks and diagnosed as having patent foramen ovale (PFO). One patient had heterozygosity for the factor V Leiden mutation, and one other had heterozygosity for prothrombin G20210A mutation. Both of them were also carriers for MTHFR 677T genotype with elevated plasma levels of homocysteine (22.3 +/- 3.9 micromol/L). These findings strongly confirm and emphasize the importance of the genetic screening for thrombotic mutations in young patients with PFO-related ischemic events in order to improve secondary prevention strategies.

Relation between inheritance of cyanotic congenital heart disease and persistent foramen ovale.

Cyanotic congenital heart disease (CCHD) usually occurs sporadically, but occasionally it is familial without evidence of Mendelian inheritance. The investigators previously reported an association between dominant inheritance of clinically significant atrial shunts (large persistent foramina ovale and small atrial septal defects) and migraine with aura in some families. In 1 family, 4 patients with CCHD were linked by relatives with atrial shunts. The presence of atrial shunts and migraine symptoms was investigated in another family in which 3 members had CCHD. Contrast echocardiography was used to detect whether atrial right-to-left shunts were present in family members. A consultant neurologist, who was blinded to cardiac findings, diagnosed and categorized migraine symptoms. In this family, relatives with atrial right-to-left shunts linked 3 members who had CCHD. There appears to be dominant inheritance of atrial shunts, which is linked to inheritance of CCHD in some families. In conclusion, it is possible that the gene responsible most often causes an atrial shunt but sometimes causes more complex heart disease.

Do common prothrombotic mutations influence the risk of cerebral ischaemia in patients with patent foramen ovale? Systematic review and meta-analysis.

Conflicting results are available on the association of prothrombotic genetic abnormalities with patent foramen ovale (PFO)-related cerebral ischaemia. We comprehensively sought and identified studies of the association of both the factor V Leiden (FV(G1691A) mutation) and the prothrombin mutation (PT(G20210A) mutation) with PFO-related cerebral ischaemia and did meta-analyses to assess the evidence for such a relation. We analysed data from six eligible studies in 856 cases and 1,001 control subjects. Additional unpublished data from a new series including 463 subjects were also entered into the analysis. The PT(G20210A) variant was significantly associated with PFO-related stroke in comparison with both control subjects (odds ratio [OR] 3.85; 95% confidence interval [CI] 2.22 to 6.66) and non-PFO-associated stroke patients (OR 2.31; 95% CI 1.20 to 4.43), whereas a trend toward an association was observed for the FV(G1691A) mutation (OR 1.18; 95% CI 0.73 to 1.90, compared to control subjects; OR 1.14; 95% CI 0.62 to 2.09, compared to non-PFO-associated stroke patients). The status of carrier of either the FV(G1691A) mutation or the PT(G20210A) variant was associated with a risk for stroke of 1.98 (95% CI 1.38 to 2.83) and 1.62 (95% CI 1.03 to 2.57), as compared to control subjects and non-PFO-associated stroke patients, respectively. Addition of common prothrombotic genetic variants to standard initial screening may contribute to stratifying PFO-associated stroke patients at different risk of ischaemic events and targeting secondary prevention strategies.

Mutations in the NKX2-5 gene in patients with stroke and patent foramen ovale.

OBJECTIVE: Patent foramen ovale (PFO) has been related to stroke but its existence has not been explained to date. NKX2-5 is the most implicated gene in fetal atrial septation. We studied NKX2-5 with respect to the presence or absence of PFO in stroke patients. METHODS: A prospective analysis of NKX2-5 regarding age, gender, PFO, right-to-left shunt (RLS) size and atrial septal aneurysm (ASA) was performed in consecutive stroke patients and in 50 controls. The entire coding region and intron-exon boundaries of NKX2-5 gene were analyzed by PCR and sequencing of DNA from peripheral lymphocytes. RESULTS: One hundred patients participated in the study (mean age 56.5+/-12.4 years, 58% males) and PFO was diagnosed in 34% of them by transesophageal echocardiography. RLS was small (12%), moderate (2%) and large (20%). ASA was present in four patients. DNA revealed a novel c.2357G>A change in one PFO patient with cryptogenic stroke. Furthermore, c.182C>T, a mutation previously described in patients with cardiac defects, was detected in two non-PFO women with cryptogenic stroke. None of these changes were detected in our controls. The c.172A>G polymorphism was found in 21% of controls. It appeared more frequently in ASA patients (p=0.084), in cryptogenic PFO stroke patients (p=0.097) and in patients with known causes of stroke (p=0.037). The c.2850C>A polymorphism was also detected in our series with no differences in PFO, RLS size or ASA. CONCLUSION: Despite the fact that the NKX2-5 could account for the persistence of PFO, mutations of this gene in peripheral blood DNA were barely detected in our study.

[A 49-year-old woman with deep vein thrombosis, pulmonary embolism, and left-sided paralysis]. / 49-jährige Patientin mit tiefer Beinvenenthrombose, Lungenembolie und linksseitiger Hemiparese.

We report the case of a 49-year-old female patient who was admitted stationary because of a left-sided paralysis which had appeared some hours before. An embolic occlusion of the right A. cerebri media turned out to be the cause. A paradoxical embolism could be assumed because of an existing deep vein thrombosis and an increased right-ventricular pressure within a hemodynamically relevant fulminant pulmonary embolism as well as the additional existence of a patent foramen ovale (PFO). Systemic lysis as treatment of the pulmonary embolism was contraindicated because slight bleeding had occurred in the area of the right basal ganglia after treatment of the embolic occlusion of the right A. cerebri media by a local lysis. Subsequently and in the acuteness, a catheter interventional PFO-closure via a double-umbrella device was placed and the pulmonary embolism was effectively treated by a local lysis through the insertion of a pigtail-catheter into the right pulmonary artery.