Genetic analysis of Yunnan sudden unexplained death by whole genome sequencing in Southwest of China

Identifying the Pathogenic Variants in Heart Genes in Vietnamese Sudden Unexplained Death Victims by Next-Generation Sequencing

In forensics, one-third of sudden deaths remain unexplained after a forensic autopsy. A majority of these sudden unexplained deaths (SUDs) are considered to be caused by inherited cardiovascular diseases. In this study, we investigated 40 young SUD cases (<40 years), with non-diagnostic structural cardiac abnormalities, using Targeted NGS (next-generation sequencing) for 167 genes previously associated with inherited cardiomyopathies and channelopathies. Fifteen cases identified 17 variants on related genes including the following: AKAP9, CSRP3, GSN, HTRA1, KCNA5, LAMA4, MYBPC3, MYH6, MYLK, RYR2, SCN5A, SCN10A, SLC4A3, TNNI3, TNNI3K, and TNNT2. Of these, eight variants were novel, and nine variants were reported in the ClinVar database. Five were determined to be pathogenic and four were not evaluated. The novel and unevaluated variants were predicted by using in silico tools, which revealed that four novel variants (c.5187_5188dup, p.Arg1730llefsTer4 in the AKAP9 gene; c.1454A>T, p.Lys485Met in the MYH6 gene; c.2535+1G>A in the SLC4A3 gene; and c.10498G>T, p.Asp3500Tyr in the RYR2 gene) were pathogenic and three variants (c.292C>G, p.Arg98Gly in the TNNI3 gene; c.683C>A, p.Pro228His in the KCN5A gene; and c.2275G>A, p.Glu759Lys in the MYBPC3 gene) still need to be further verified experimentally. The results of our study contributed to the general understanding of the causes of SUDs. They provided a scientific basis for screening the risk of sudden death in family members of victims. They also suggested that the Targeted NGS method may be used to identify the pathogenic variants in SUD victims.

From the sideline: Tissue-specific nucleoporin function in health and disease, an update

The subcellular compartmentalisation of eukaryotic cells requires selective exchange between the cytoplasm and the nucleus. Intact nucleocytoplasmic transport is vital for normal cell function and mutations in the executing machinery have been causally linked to human disease. Central players in nucleocytoplasmic exchange are nuclear pore complexes (NPCs), which are built from ~30 distinct proteins collectively termed nucleoporins. Aberrant nucleoporin expression was detected in human cancers and autoimmune diseases since quite some time, while it was through the increasing use of next generation sequencing that mutations in nucleoporin genes associated with mainly rare hereditary diseases were revealed. The number of newly identified mutations is steadily increasing, as is the number of diseases. Mutational hotspots have emerged: mutations in the scaffold nucleoporins seemingly affect primarily inner organs, such as heart, kidney, and ovaries, whereas genetic alterations in peripheral, cytoplasmic nucleoporins affect primarily the central nervous system and development. In this review, we summarise latest insights on altered nucleoporin function in the context of human hereditary disorders, with a focus on those where mechanistic insights are beginning to emerge.

Whole exome sequencing with a focus on cardiac disease-associated genes in families of sudden unexplained deaths in Yunnan, southwest of China

OBJECTIVES

To explore the causes of sudden unexpected death (SUD) and to search for high-risk people, whole exome sequencing (WES) was performed in families with SUDs.  METHODS: Whole exome sequencing of 25 people from 14 SUD families were screened based on cardiac disease-associated gene variants, and their echocardiograms and electrocardiograms (ECG) were also examined. The protein function of mutated genes was predicted by SIFT, PolyPhen2 and Mutation Assessor.

RESULTS

In the group of 25 people from 14 SUD families, 49 single nucleotide variants (SNVs) of cardiac disease-associated genes were found and verified by Sanger sequencing. 29 SNVs of 14 cardiac disorder-related genes were predicted as pathogens by software. Among them, 7 SNVs carried by two or more members were found in 5 families, including SCN5A (c.3577C > T), IRX4 (c.230A > G), LDB3 (c.2104 T > G), MYH6 (c.3G > A), MYH6 (c.3928 T > C), TTN (c.80987C > T) and TTN (c.8069C > T). 25 ECGs were collected. In summary, 4 people had J-point elevation, 2 people had long QT syndrome (LQTS), 4 people had prolonged QT interval, 3 people had T-wave changes, 3 people had sinus tachycardia, 4 people had sinus bradycardia, 4 people had left side of QRS electrical axis, and 3 people had P wave broadening. Echocardiographic results showed that 1 person had atrial septal defect, 1 person had tricuspid regurgitation, and 2 people had left ventricular diastolic dysfunction.

CONCLUSIONS

Of the 14 heart disease-associated genes in 14 SUDs families, there are 7 possible pathological SNVS may be associated with SUDs. Our results indicate that people with ECG abnormalities, such as prolonged QT interval, ST segment changes, T-wave change and carrying the above 7 SNVs, should be the focus of prevention of sudden death.

AKAP9-Related Channelopathy: Novel Pathogenic Variant and Review of the Literature

Disease-associated pathogenic variants in the A-Kinase Anchor Protein 9 (AKAP9) (MIM *604001) have been recently identified in patients with autosomal dominant long QT syndrome 11 (MIM #611820), lethal arrhythmia (ventricular fibrillation, polymorphic ventricular tachycardia), Brugada syndrome, and sudden unexpected death. However, AKAP9 sequence variations were rarely reported and AKAP9 was classified as a "disputed evidence" gene to support disease causation due to the insufficient genetic evidence and a limited number of reported AKAP9-mutated patients. Here, we describe a 47-year-old male carrying a novel frameshift AKAP9 pathogenic variant who presented recurrent syncopal attacks and sudden cardiac arrest that required a semi-automatic external defibrillator implant and an electric shock treatment of ventricular arrhythmia. This study provides insight into the mechanism underlying cardiac arrest and confirms that AKAP9 loss-of-function variants predispose to serious, life-threatening ventricular arrhythmias.