Introduction:
Current screening for mutations in human disease is turning increasingly to next-generation methods that map short reads to a reference sequence. We report here an unusual variant that was undetected by next generation sequencing in a patient diagnosed with Jervell Lange-Nielsen syndrome (JLNS) and initial results in an induced pluripotent stem cell-derived cardiomyocyte (iPSC-CM) model.
Methods and Results:
A diagnosis of JLNS was made in a middle-aged woman with congenital deafness and QT intervals as long as 800 msec. However, next-generation sequencing found only a heterozygous
KCNQ1
mutation, R518X. Convinced by the clinical phenotype that a second causative variant was highly likely, we used Sanger sequencing of PCR KCNQ1 amplicons to identify a 36-basepair poly-adenine tract, encoding 12 lysines, inserted within the coding sequence at the 5’ end of exon 15. Electrophysiological studies in patient-specific IPSC-CMs revealed marked prolongation of ventricular-like action potentials (Figure).
Conclusion:
Long inserts of the type we identified here have not been previously reported in the long QT syndromes. We speculate that next generation-based short reads containing this variant could not be mapped to a reference sequence and thus this type of variant will be missed by next-generation analysis unless bioinformatics filters are specifically modified to include this possibility. Validation of this long QT syndrome iPSC-CM model provides a human cell based platform for drug discovery and mechanistic studies to further our understanding of disease pathogenesis.
Combining Induced Pluripotent Stem Cell with Next Generation Sequencing Technology to Gain New Insights into Pathobiology and Treatment of Pulmonary Arterial Hypertension