A cardio-neurological form of laminopathy: dilated cardiomyopathy with permanent partial atrial standstill and axonal neuropathy

Atrial cardiomyopathy revisited-evolution of a concept: a clinical consensus statement of the European Heart Rhythm Association (EHRA) of the ESC, the Heart Rhythm Society (HRS), the Asian Pacific Heart Rhythm Society (APHRS), and the Latin American Heart Rhythm Society (LAHRS)

AIMS

The concept of "atrial cardiomyopathy" (AtCM) had been percolating through the literature since its first mention in 1972. Since then, publications using the term were sporadic until the decision was made to convene an expert working group with representation from four multinational arrhythmia organizations to prepare a consensus document on atrial cardiomyopathy in 2016 (EHRA/HRS/APHRS/SOLAECE expert consensus on atrial cardiomyopathies: definition, characterization, and clinical implication). Subsequently, publications on AtCM have increased progressively.

METHODS AND RESULTS

The present consensus document elaborates the 2016 AtCM document further to implement a simple AtCM staging system (AtCM stages 1-3) by integrating biomarkers, atrial geometry, and electrophysiological changes. However, the proposed AtCM staging needs clinical validation. Importantly, it is clearly stated that the presence of AtCM might serve as a substrate for the development of atrial fibrillation (AF) and AF may accelerates AtCM substantially, but AtCM per se needs to be viewed as a separate entity.

CONCLUSION

Thus, the present document serves as a clinical consensus statement of the European Heart Rhythm Association (EHRA) of the ESC, the Heart Rhythm Society (HRS), the Asian Pacific Heart Rhythm Society (APHRS), and the Latin American Heart Rhythm Society (LAHRS) to contribute to the evolution of the AtCM concept.

Atrial standstill associated with lamin A/C mutation: A case report

The case report shares evidence for a better understanding of atrial standstill. This being a rare arrhythmogenic condition. This is a 46-year-old woman presented with multiple sites of arterial embolism, including lower extremity arteries, coronary artery, and cerebral artery. Unexpectedly, multiple arterial embolization in the patient was due to atrial standstill by transthoracic echocardiography and cardiac electrophysiological study. An additional family investigation revealed that the patient's brother and sister also suffered from this disease. In search of further understanding the case, we carried out the genetic testing of the family and a frame shift double-G insertion mutation at c.1567 in the LMNA gene was found in all the three individuals. The patient recovered well after anticoagulation therapy and left bundle branch area pacing. This report remarks on the importance of multiple sites of arterial embolism which should be wary of family atrial standstill.

Genetic risk factors for VIPN in childhood acute lymphoblastic leukemia patients identified using whole-exome sequencing

AIM

To identify genetic markers associated with vincristine-induced peripheral neuropathy (VIPN) in childhood acute lymphoblastic leukemia.

PATIENTS & METHODS

Whole-exome sequencing data were combined with exome-wide association study to identify predicted-functional germline variants associated with high-grade VIPN. Genotyping was then performed for top-ranked signals (n = 237), followed by validation in independent replication group (n = 405).

RESULTS

Minor alleles of rs2781377/SYNE2 (p = 0.01) and rs10513762/MRPL47 (p = 0.01) showed increased risk, whereas that of rs3803357/BAHD1 had a protective effect (p = 0.007). Using a genetic model based on weighted genetic risk scores, an additive effect of combining these loci was observed (p = 0.003). The addition of rs1135989/ACTG1 further enhanced model performance (p = 0.0001).

CONCLUSION

Variants in SYNE2, MRPL47 and BAHD1 genes are putative new risk factors for VIPN in childhood acute lymphoblastic leukemia.

Current insights into LMNA cardiomyopathies: Existing models and missing LINCs

The nuclear lamina is a critical structural domain for the maintenance of genomic stability and whole-cell mechanics. Mutations in the LMNA gene, which encodes nuclear A-type lamins lead to the disruption of these key cellular functions, resulting in a number of devastating diseases known as laminopathies. Cardiomyopathy is a common laminopathy and is highly penetrant with poor prognosis. To date, cell mechanical instability and dysregulation of gene expression have been proposed as the main mechanisms driving cardiac dysfunction, and indeed discoveries in these areas have provided some promising leads in terms of therapeutics. However, important questions remain unanswered regarding the role of lamin A dysfunction in the heart, including a potential role for the toxicity of lamin A precursors in LMNA cardiomyopathy, which has yet to be rigorously investigated.

A novel nonsense mutation in LMNA gene identified by Exome Sequencing in an atrial fibrillation family

Genetic factor plays an important role in cardiac arrhythmias. Several loci have been identified associated with this disease. However, they only explained parts of it and more genes and loci remain to be identified. In present study, we recruited a four generation family from the north of China. Four members of this family were diagnosed with atrial fibrillation by electrocardiogram (ECG). We used Exome Sequencing and Sanger sequencing to explore the candidate mutation for cardiac arrhythmia in this family. A nonsense mutation (c.G1494A, p.Trp498Ter) in the LMNA gene were identified as the candidate mutation. This variant is a novel mutation and has not yet been reported for any actual databases. This novel mutation co-segregated exactly with the disease in this family. Meanwhile, it was not detected in 524 control subjects of matched ancestry. According to structural model prediction, the mutation is expected to affect the Lamin Tail Domain (LTD) of lamin A/C protein. So the nonsense mutation discovered in the family probably was a novel mutation associated with familial atrial fibrillation. This discovery expands the mutation spectrum of LMNA and indicates the importance of LMNA in AF.

Genetic and clinical characteristics of skeletal and cardiac muscle in patients with lamin A/C gene mutations

Alterations of the lamin A/C (LMNA) gene are associated with different clinical entities, including disorders that affect skeletal and cardiac muscle, peripheral nerves, metabolism, bones, and disorders that cause premature aging. In this article we review the clinical and genetic characteristics of cardiac and skeletal muscle diseases related to alterations in the LMNA gene. There is no single explanation of how LMNA gene alterations may cause these disorders; however, important goals have been achieved in understanding the pathogenic effects of LMNA gene mutations on cardiac and skeletal muscle.

Autosomal recessive atrial dilated cardiomyopathy with standstill evolution associated with mutation of Natriuretic Peptide Precursor A

BACKGROUND

Atrial dilatation and atrial standstill are etiologically heterogeneous phenotypes with poorly defined nosology. In 1983, we described 8-years follow-up of atrial dilatation with standstill evolution in 8 patients from 3 families. We later identified 5 additional patients with identical phenotypes: 1 member of the largest original family and 4 unrelated to the 3 original families. All families are from the same geographic area in Northeast Italy.

METHODS AND RESULTS

We followed up the 13 patients for up to 37 years, extended the clinical investigation and monitoring to living relatives, and investigated the genetic basis of the disease. The disease was characterized by: (1) clinical onset in adulthood; (2) biatrial dilatation up to giant size; (3) early supraventricular arrhythmias with progressive loss of atrial electric activity to atrial standstill; (4) thromboembolic complications; and (5) stable, normal left ventricular function and New York Heart Association functional class during the long-term course of the disease. By linkage analysis, we mapped a locus at 1p36.22 containing the Natriuretic Peptide Precursor A gene. By sequencing Natriuretic Peptide Precursor A, we identified a homozygous missense mutation (p.Arg150Gln) in all living affected individuals of the 6 families. All patients showed low serum levels of atrial natriuretic peptide. Heterozygous mutation carriers were healthy and demonstrated normal levels of atrial natriuretic peptide.

CONCLUSIONS

Autosomal recessive atrial dilated cardiomyopathy is a rare disease associated with homozygous mutation of the Natriuretic Peptide Precursor A gene and characterized by extreme atrial dilatation with standstill evolution, thromboembolic risk, preserved left ventricular function, and severely decreased levels of atrial natriuretic peptide.

Behavioral and molecular exploration of the AR-CMT2A mouse model Lmna (R298C/R298C)

In 2002, we identified LMNA as the first gene responsible for an autosomal recessive axonal form of Charcot-Marie-Tooth disease, AR-CMT2A. All patients were found to be homozygous for the same mutation in the LMNA gene, p.Arg298Cys. In order to investigate the physiopathological mechanisms underlying AR-CMT2A, we have generated a knock-in mouse model for the Lmna p.Arg298Cys mutation. We have explored these mice through an exhaustive series of behavioral tests and histopathological analyses, but were not able to find any peripheral nerve phenotype, even at 18 months of age. Interestingly at the molecular level, however, we detect a downregulation of the Lmna gene in all tissues tested from the homozygous knock-in mouse Lmna (R298C/R298C) (skeletal muscle, heart, peripheral nerve, spinal cord and cerebral trunk). Importantly, we further reveal a significant upregulation of Pmp22, specifically in the sciatic nerves of Lmna (R298C/R298C) mice. These results indicate that, despite the absence of a perceptible phenotype, abnormalities exist in the peripheral nerves of Lmna (R298C/R298C) mice that are absent from other tissues. Although the mechanisms leading to deregulation of Pmp22 in Lmna (R298C/R298C) mice are still unclear, our results support a relation between Lmna and Pmp22 and constitute a first step toward understanding AR-CMT2A physiopathology.