Molecular mechanisms of hypoplastic left heart syndrome

Das hypoplastische Linksherzsyndrom (HLHS) stellt ein kongenitales Herz- und Gefäßfehlbildungssyndrom dar, welches durch eine Atresie oder Stenose der Aorten- und Mitralklappe sowie eine Hypoplasie des linken Ventrikels und der Aorta gekennzeichnet ist. Das HLHS ist unbehandelt ursächlich für 25 bis 40 % der neonatalen kardialen Todesfälle und gehört zu den schwerwiegendsten kongenitalen Herzfehlbildungen (CHDs). Die Ätiologie des HLHS ist bis heute weitgehend unklar. Um die molekularen Mechanismen in der Entstehung des HLHS zu untersuchen, wurden in dieser Arbeit Analysen auf Genom-, Epigenom- und Transkriptomebene an Keimbahn- bzw. Herzgewebematerial von Patienten mit HLHS und anderen CHDs durchgeführt. Dies umfasste auf Keimbahnebene Gesamt-Exom-Sequenzierungs (WES)-Analysen von Familien mit Catel-Manzke-Syndrom sowie von Familien mit nicht-syndromalen HLHS-Fällen. Auf somatischer Ebene wurden Herzgewebeproben von HLHS-Patienten hinsichtlich pathogener Mutationen untersucht und RNA-Sequenzierungen durchgeführt. Zudem erfolgten DNA-Methylierungsanalysen an Herzgewebe von Patienten mit HLHS und anderen CHDs. Auf Keimbahnebene ließen sich kausale Genvarianten im TGDS-Gen bei drei Familien mit Catel-Manzke-Syndrom und eine kausale de novo Splice-Donor-Mutation in NR2F2 bei einem nicht-syndromalen Fall mit HLHS nachweisen. Neben potenziell krankheitsrelevanten Genvarianten in C15orf62, TNKS1BP1 und PRF1 im familiären Kontext konnten auf somatischer Ebene im Herzgewebe der HLHS-Patienten funktionelle Mutationen in Genen kardialer Entwicklungsprozesse, wie z.B. NOTCH1, detektiert werden. Des Weiteren ließen sich erstmalig in primärem Herzgewebe von Patienten mit CHDs herzregionspezifische DNA-Methylierungsprofile nachweisen. Die Ergebnisse dieser Arbeit lassen vermuten, dass prädisponierende vererbte Genvarianten in Kombination mit somatischen Mutationen und epigenetischen Aberrationen im Herzgewebe der Patienten in der Pathogenese des HLHS involviert sind.Hypoplastic left heart syndrome (HLHS) displays a severe congenital heart defect (CHD) that encompasses a spectrum of structural defects characterized by atresia or stenosis of the aortic and mitral valve, as well as a hypoplasia of the left ventricle and aorta. HLHS, if left untreated, is responsible for 25 to 40 % of all neonatal cardiac deaths and represents one of the most severe cardiac malformations. The etiology of HLHS still remains unknown. In order to investigate the molecular mechanisms of HLHS, heart tissue and blood samples from different patients with HLHS, as well as from patients displaying other CHDs, have been examined. Genomic, transcriptomic and epigenomic datasets have been generated and analyzed in this thesis. This included a whole exome sequencing (WES) dataset from families with Catel-Manzke syndrome and from families with non-syndromic HLHS. In order to analyze somatic changes potentially involved in the pathogenesis of HLHS, WES and RNA sequencing was performed on heart tissue samples from independent cases. To further evaluate epigenetic alterations, DNA methylation profiles of heart tissue samples from cases with HLHS and different CHDs have been analyzed. Disease-causing mutations in TGDS have been identified in three families with Catel-Manzke syndrome. Furthermore, a de novo donor splice site mutation has been detected as a disease-causing variant in a case with HLHS. A family-based analysis revealed possibly disease-causing mutations in C15orf62, TNKS1BP1 und PRF1. Despite these findings, the analysis on heart tissue samples revealed functional variants in genes which are possibly linked to heart development, such as NOTCH1. For the first time, heart region specific DNA methylation profiles have been detected. The results of the present study suggest that predisposing inherited genetic variants acting in combination with somatic mutations and epigenetic aberrations in cardiac tissue might be involved in the pathogenesis of HLHS

Rare variants in NR2F2 cause congenital heart defects in humans

Congenital heart defects (CHDs) are the most common birth defect worldwide and are a leading cause of neonatal mortality. Nonsyndromic atrioventricular septal defects (AVSDs) are an important subtype of CHDs for which the genetic architecture is poorly understood. We performed exome sequencing in 13 parent-offspring trios and 112 unrelated individuals with nonsyndromic AVSDs and identified five rare missense variants (two of which arose de novo) in the highly conserved gene NR2F2, a very significant enrichment (p = 7.7 × 10?7) compared to 5,194 control subjects. We identified three additional CHD-affected families with other variants in NR2F2 including a de novo balanced chromosomal translocation, a de novo substitution disrupting a splice donor site, and a 3 bp duplication that cosegregated in a multiplex family. NR2F2 encodes a pleiotropic developmental transcription factor, and decreased dosage of NR2F2 in mice has been shown to result in abnormal development of atrioventricular septa. Via luciferase assays, we showed that all six coding sequence variants observed in individuals significantly alter the activity of NR2F2 on target promoters

Distinct genetic architectures for syndromic and nonsyndromic congenital heart defects identified by exome sequencing.

Congenital heart defects (CHDs) have a neonatal incidence of 0.8-1% (refs. 1,2). Despite abundant examples of monogenic CHD in humans and mice, CHD has a low absolute sibling recurrence risk (∼2.7%), suggesting a considerable role for de novo mutations (DNMs) and/or incomplete penetrance. De novo protein-truncating variants (PTVs) have been shown to be enriched among the 10% of 'syndromic' patients with extra-cardiac manifestations. We exome sequenced 1,891 probands, including both syndromic CHD (S-CHD, n = 610) and nonsyndromic CHD (NS-CHD, n = 1,281). In S-CHD, we confirmed a significant enrichment of de novo PTVs but not inherited PTVs in known CHD-associated genes, consistent with recent findings. Conversely, in NS-CHD we observed significant enrichment of PTVs inherited from unaffected parents in CHD-associated genes. We identified three genome-wide significant S-CHD disorders caused by DNMs in CHD4, CDK13 and PRKD1. Our study finds evidence for distinct genetic architectures underlying the low sibling recurrence risk in S-CHD and NS-CHD

Homozygous and Compound-Heterozygous Mutations in TGDS Cause Catel-Manzke Syndrome

Catel-Manzke syndrome is characterized by Pierre Robin sequence and a unique form of bilateral hyperphalangy causing a clinodactyly of the index finger. We describe the identification of homozygous and compound heterozygous mutations in TGDS in seven unrelated individuals with typical Catel-Manzke syndrome by exome sequencing. Six different TGDS mutations were detected: c.892A>G (p.Asn298Asp), c.270_271del (p.Lys91Asnfs*22), c.298G>T (p.A1a100Ser), c.294T>G (p.Phe98Leu), c.269A>G (p.G1u90Gly), and c.700T>C (p.Tyr234His), all predicted to be disease causing. By using haplotype reconstruction we showed that the mutation c.298G>T is probably a founder mutation. Due to the spectrum of the amino acid changes, we suggest that loss of function in TGDS is the underlying mechanism of Catel-Manzke syndrome. TGDS (dTDP-D-glucose 4,6-dehydrogenase) is a conserved protein belonging to the SDR family and probably plays a role in nucleotide sugar metabolism

Loss of ADAMTS19 causes progressive non-syndromic heart valve disease

International audienc

Rare Variants in NR2F2 Cause Congenital Heart Defects in Humans (vol 94, pg 574, 2014)

status: publishe

Rare Variants in NR2F2 Cause Congenital Heart Defects in Humans (vol 94, pg 574, 2014)

status: publishe