In-frame Variants in FLNA Proximal Rod 1 Domain Associate With a Predominant Cardiac Valvular Phenotype

Abstract

Introduction and objectives: X-linked cardiac valvular dysplasia is a rare form of male-specific congenital heart defect mainly characterized by myxomatous degeneration of the atrioventricular valves with variable hemodynamic consequences. It is caused by genetic defects in FLNA-encoded filamin A, a widely expressed actin-binding protein that regulates cytoskeleton organization. Filamin A loss of function has also been associated with often concurring neurologic and connective tissue manifestations, with mutations in the first half of the Rod 1 domain apparently expressing the full cardiac phenotype. We contribute to previous genotype-phenotype correlations with a multidisciplinary approach in a newly-described family.

Methods: Cardiologic, dysmorphologic, and genetic evaluation of available members were complemented with transcriptional and X-chromosome inactivation studies.

Results: A novel FLNA mutation c.1066-3C>G cosegregated with a male-expressed, apparently isolated, cardiac phenotype with no skewed X-inactivation pattern in female carriers. This variant was shown to result in an in-frame deletion of 8 amino acid residues near the N-terminal region of the protein.

Conclusions: A nonimprinted, partial loss of function of filamin A proximal Rod 1 domain seems to be the pathogenetic mechanism of cardiac valvular dysplasia, with some cases occasionally expressing associated extracardiac manifestations.

Keywords: Cardiac valvular dysplasia; Displasia valvular cardiaca; Enfermedad ligada al cromosoma X; FLNA mutation; Mutación en FLNA; X-linked disease.