How heart cell mosaicism can cause arrhythmia

How heart cell mosaicism can cause arrhythmia

Long-QT syndrome (LQTS) can result in life-threatening abnormal heart rhythms called arrhythmias. When undergoing commercial genetic testing for LQTS, almost a third of patients receive a negative test result, suggesting the presence of other undiscovered genetic variants associated with the disease.

Researchers found a disease-causing genetic variation present only in a fraction of heart cells, a phenomenon called somatic mosaicism, in a premature infant with LQTS and arrhythmia. Using rapid genome sequencing, the authors identified a mutation in the 3-day-old infant.

When examined in cellular experiments, the mutation altered the function of a sodium channel gene that causes LQTS. Unlike most previously reported LQTS cases, the mutation was present in the genomes of only 8% of the patient cells.

To better understand how such a small fraction of abnormal heart cells could cause arrhythmia, the authors developed a computational model of heart electrophysiology that incorporated somatic mosaicism, and examined the prevalence of mosaicism in a population of 7,500 individuals genetically tested for arrhythmia.

The authors found four individuals with mosaicism in a gene causing LQTS. The findings demonstrate how mosaicism in a small fraction of heart cells can cause LQTS and indicate that somatic mosaicism is a rare cause of genetic arrhythmias, according to the authors.

http://www.pnas.org/content/113/41/11555

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