Early-onset multivalvular disease caused by a missense variant in lamin A/C

Abstract

Lamins A/C, coded by LMNA gene, are crucial for nuclear architecture preservation. Pathogenic LMNA variants cause a wide range of inherited diseases called "laminopathies". A subgroup is referred to "progeroid syndromes" characterized by premature aging and other manifestations including cardiac valve abnormalities. Atypical phenotypes, generally less severe, have also been reported. We report the case of a 26-year-old male with calcific tricuspid aortic and mitral valve diseases. His father was diagnosed with severe aortic valve stenosis and mitral annulus calcification at the age of 38. The goal of this study was to identify the putative variant causing this non-syndromic multivalvular disease. Known disease-causing variants in NOTCH1, FLNA, and DCHS1 were first excluded by Sanger sequencing. Whole-exome sequencing was then performed in five family members. A LMNA variant (p.Glu262Val) was identified with in silico evidences of pathogenicity (CADD [combined annotation dependent depletion] = 33). Cells transfected with the cDNA construct harboring p.Glu262Val were characterized by abnormal nuclear morphology. Along with a literature review, the variant was classified as likely pathogenic. Elucidating the mechanism by which LMNA p.Glu262Val specifically affects cardiac heart valves is likely to provide insight about the pathogenesis of Mendelian forms of valvular heart diseases and may help guide the development of therapies.

Keywords: family study; functional study; lamin A/C; multivalvular disease; whole exome sequencing.

Figure 1

Family pedigree and phenotype (A) Family pedigree. Each symbol indicates a female (circle) or male (square) family member. Black symbols indicate affected individuals, gray ones indicate unaffected family members and white ones indicate unphenotyped relatives. The text immediately below the symbols gives the family member ID; age at the echocardiogram evaluation or age of death when applicable (presented as age of diagnosis/age of death); and the LMNA Glu262Val variant status. A diagonal line across symbol indicates that the individual is deceased. The index case (black arrow) of this family is individual III:2. (B–D) Two-dimensional echocardiography of the proband. (B) Parasternal long-axis view. (C) Parasternal short-axis view of the aortic valve. (D) Transaortic valvular flow velocity measured by continuous-wave Doppler ultrasound. Red star: calcification of the base of the left-coronary aortic valve cusp. Red arrow: thickening and calcification of the posterior mitral valve leaflet.

Figure 2

Variant p.Glu262Val in LMNA (A) Exon-intron structure of LMNA. Red vertical line indicates the variant p.Glu262Val, c.785A>T. (B) Corresponding protein domains. Red arrow indicates the p.Glu262Val variant. (C) Alignment of LMNA amino acid sequences across species. LMNA, Lamin A/C.

Figure 3

Nuclear abnormalities in p.Glu262Val transfected cells (A) Fluorescence of nuclei shape from a negative control (wild-type), a positive control (p.D300G) and our variant of interest (p.E262V). Arrows indicate abnormal lamin A/C localization. (B–D) ImageJ analysis of nuclear morphology for area (B), perimeter (C), and nuclear contour ratio (D). Unpaired t test was performed using GraphPad Prism version 8.0.1 (ns, not significant; ∗p < 0.05, ∗∗p < 0.01, ∗∗∗p < 0.001, ∗∗∗∗p < 0.0001). The results are shown as mean ± standard deviation.