Compound heterozygous NOTCH1 mutations underlie impaired cardiogenesis in a patient with hypoplastic left heart syndrome

Abstract

Hypoplastic left heart syndrome (HLHS) is a severe congenital heart defect (CHD) that necessitates staged, single ventricle surgical palliation. An increased frequency of bicuspid aortic valve (BAV) has been observed among relatives. We postulated number of mutant alleles as a molecular basis for variable CHD expression in an extended family comprised of an HLHS proband and four family members who underwent echocardiography and whole-genome sequencing (WGS). Dermal fibroblast-derived induced pluripotent stem cells (iPSC) were procured from the proband-parent trio and bioengineered into cardiomyocytes. Cardiac phenotyping revealed aortic valve atresia and a slit-like left ventricular cavity in the HLHS proband, isolated bicuspid pulmonary valve in his mother, BAV in a maternal 4° relative, and no CHD in his father or sister. Filtering of WGS for rare, functional variants that segregated with CHD and were compound heterozygous in the HLHS proband identified NOTCH1 as the sole candidate gene. An unreported missense mutation (P1964L) in the cytoplasmic domain, segregating with semilunar valve malformation, was maternally inherited and a rare missense mutation (P1256L) in the extracellular domain, clinically silent in the heterozygous state, was paternally inherited. Patient-specific iPSCs exhibited diminished transcript levels of NOTCH1 signaling pathway components, impaired myocardiogenesis, and a higher prevalence of heterogeneous myofilament organization. Extended, phenotypically characterized families enable WGS-derived variant filtering for plausible Mendelian modes of inheritance, a powerful strategy to discover molecular underpinnings of CHD. Identification of compound heterozygous NOTCH1 mutations and iPSC-based functional modeling implicate mutant allele burden and impaired myogenic potential as mechanisms for HLHS.

The complex genetics of hypoplastic left heart syndrome

“…5c). A notable observation was the recovery of the Notch pathway, given previously reported findings of Notch1 variants in subjects with HLHS 10,11 , with 12 NOTCH-related mutations identified in 8 genes from 12 subjects (Supplementary Table 5). Also recovered were genes in the TGFβ pathway, with eight mutations in eight subjects (Supplementary Table 6).…”

“…Mutations in five Notch-related genes ( Rbpj, Ep300, Nap1l1, Ncoa1 , and Tspan12 ), a pathway implicated in HLHS 10,11 , were identified. Network analysis 12 identified seven interconnected functional modules (0.64 modularity; 2.7 scaled modularity) significantly different from random networks (0.59 ± 0.019 modularity ( n = 1,000, mean ± s.d.…”

Genetic basis of aortic valvular disease

“…tetralogy of Fallot)[13]. Additional reports support this finding that mutations in NOTCH1 cause malformations of the right and left sided cardiac outflow tract within families [11,14,15]. The other gene linked to BAV in humans is GATA5 , where rare sequence variants in GATA5 were identified in patients with BAV by multiple groups [16,17,18].…”

Wnt11 regulates cardiac chamber development and disease during perinatal maturation

“…Among the different developmental signals (21)(22)(23), Wnt signaling pathways play prominent roles in cardiac precursor's commitment, cell proliferation, differentiation, and fate (24)(25)(26)(27)(28)(29)(30)(31)(32)(33)(34)(35).Actions by the Wnt family molecules can be classified into the canonical Wnt/β-catenin-dependent pathway and the noncanonical pathway, which is generally β-catenin independent, and its function can be mediated by 2 distinct modules of the noncanonical signaling: (a) the planar cell polarity (PCP) pathway; and (b) the Wnt/ Ca 2+ pathway, which involves calmodulin-dependent kinase II (CamKII), protein kinase C (PKC), and calcineurin. These factors may coordinate important cellular signaling processes including regulating the expression of key cell cycle regulators.…”