Genetic Mosaicism in Calmodulinopathy.

Wren LM, Jiménez-Jáimez J, Al-Ghamdi S, Al-Aama JY, Bdeir A, Al-Hassnan ZN, Kuan JL, Foo RY, Potet F, Johnson CN, Aziz MC, Carvill GL, Kaski JP, Crotti L, Perin F, Monserrat L, Burridge PW, Schwartz PJ, Chazin WJ, Bhuiyan ZA, George AL
Circ Genom Precis Med. 2019 12 (9): 375-385

PMID: 31454269 · PMCID: PMC6751013 · DOI:10.1161/CIRCGEN.119.002581

BACKGROUND - CaM (calmodulin) mutations are associated with congenital arrhythmia susceptibility (calmodulinopathy) and are most often de novo. In this report, we sought to broaden the genotype-phenotype spectrum of calmodulinopathies with 2 novel calmodulin mutations and to investigate mosaicism in 2 affected families.

METHODS - CaM mutations were identified in 4 independent cases by DNA sequencing. Biochemical and electrophysiological studies were performed to determine functional consequences of each mutation.

RESULTS - Genetic studies identified 2 novel CaM variants (-E141K in 2 cases; -E141V) and one previously reported CaM pathogenic variant (-D130G) among 4 probands with shared clinical features of prolonged QTc interval (range 505-725 ms) and documented ventricular arrhythmia. A fatal outcome occurred for 2 of the cases. The parents of all probands were asymptomatic with normal QTc duration. However, 2 of the families had multiple affected offspring or multiple occurrences of intrauterine fetal demise. The mother from the family with recurrent intrauterine fetal demise exhibited the -E141K mutant allele in 25% of next-generation sequencing reads indicating somatic mosaicism, whereas -D130G was present in 6% of captured molecules of the paternal DNA sample, also indicating mosaicism. Two novel mutations (E141K and E141V) impaired Ca binding affinity to the C-domain of CaM. Human-induced pluripotent stem cell-derived cardiomyocytes overexpressing mutant or wild-type CaM showed that both mutants impaired Ca-dependent inactivation of L-type Ca channels and prolonged action potential duration.

CONCLUSIONS - We report 2 families with somatic mosaicism associated with arrhythmogenic calmodulinopathy, and demonstrate dysregulation of L-type Ca channels by 2 novel CaM mutations affecting the same residue. Parental mosaicism should be suspected in families with unexplained fetal arrhythmia or fetal demise combined with a documented CaM mutation.

MeSH Terms (15)

Arrhythmias, Cardiac Base Sequence Calcium Calmodulin Child, Preschool Electrophysiology Female Genetic Predisposition to Disease Humans Infant Infant, Newborn Male Mosaicism Mutation, Missense Pedigree

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