Exogenous WNT5A and WNT11 proteins rescue CITED2 dysfunction in mouse embryonic stem cells and zebrafish morphants

Mutations and inadequate methylation profiles of CITED2 are associated with human congenital heart disease (CHD). In mouse, Cited2 is necessary for embryogenesis, particularly for heart development, and its depletion in embryonic stem cells (ESC) impairs cardiac differentiation. We have now determined that Cited2 depletion in ESC affects the expression of transcription factors and cardiopoietic genes involved in early mesoderm and cardiac specification. Interestingly, the supplementation of the secretome prepared from ESC overexpressing CITED2, during the onset of differentiation, rescued the cardiogenic defects of Cited2-depleted ESC. In addition, we demonstrate that the proteins WNT5A and WNT11 held the potential for rescue. We also validated the zebrafish as a model to investigate cited2 function during development. Indeed, the microinjection of morpholinos targeting cited2 transcripts caused developmental defects recapitulating those of mice knockout models, including the increased propensity for cardiac defects and severe death rate. Importantly, the co-injection of anti-cited2 morpholinos with either CITED2 or WNT5A and WNT11 recombinant proteins corrected the developmental defects of Cited2-morphants. This study argues that defects caused by the dysfunction of Cited2 at early stages of development, including heart anomalies, may be remediable by supplementation of exogenous molecules, offering the opportunity to develop novel therapeutic strategies aiming to prevent CHD.Agência financiadora: Fundação para a Ciência e a Tecnologia (FCT) Comissão de Coordenação e Desenvolvimento Regional do Algarve (CCDR Algarve) ALG-01-0145-FEDER-28044; DFG 568/17-2 Algarve Biomedical Center (ABC) Municipio de Louléinfo:eu-repo/semantics/publishedVersio

Founder mutation in N-terminus of cardiac troponin I causes malignant hypertrophic cardiomyopathy

Background - Cardiac troponin I (TNNI3) gene mutations account for 3% of hypertrophic cardiomyopathy and carriers have a heterogeneous phenotype, with increased risk of sudden cardiac death. Only one mutation (p.Arg21Cys) has been reported in the N-terminus of the protein. In model organisms, it impairs protein kinase A phosphorylation, increases calcium sensitivity, and causes diastolic dysfunction. The phenotype of this unique mutation in hypertrophic cardiomyopathy patients remains unknown. Methods - We sequenced 29 families with hypertrophic cardiomyopathy enriched for pediatric-onset disease and identified 5 families with the TNNI3 p.Arg21Cys mutation. Using cascade screening, we studied the clinical phenotype of 57 individuals from the 5 families with TNNI3 p.Arg21Cys-related cardiomyopathy. We performed survival analysis investigating the age at first sudden cardiac death in carriers of the mutation. Results - All five families with TNNI3 p.Arg21Cys were from south Lebanon. TNNI3 p.Arg21Cys-related cardiomyopathy manifested a malignant phenotype - sudden cardiac death occurred in 30 (53%) of 57 affected individuals at median age of 22.5 years. In select carriers without left ventricular hypertrophy on echocardiogram, sudden cardiac death occurred, myocyte disarray was found on autopsy heart, and tissue doppler and cardiac magnetic resonance imaging identified subclinical disease features such as diastolic dysfunction and late-gadolinium enhancement. Conclusions - The TNNI3 p.Arg21Cys mutation has a founder effect in south Lebanon and causes malignant hypertrophic cardiomyopathy with early sudden cardiac death even in the absence of hypertrophy. Genetic diagnosis with this mutation may be sufficient for risk stratification for sudden cardiac death