Molecular and cellular evidence for the impact of a hypertrophic cardiomyopathy-associated RAF1 variant on the structure and function of contractile machinery in bioartificial cardiac tissues

• Published in: Communications biology Vol. 6; no. 1; p. 657
• Main Authors: Nakhaei-Rad, Saeideh, Haghighi, Fereshteh, Bazgir, Farhad, Dahlmann, Julia, Busley, Alexandra Viktoria, Buchholzer, Marcel, Kleemann, Karolin, Schänzer, Anne, Borchardt, Andrea, Hahn, Andreas, Kötter, Sebastian, Schanze, Denny, Anand, Ruchika, Funk, Florian, Kronenbitter, Annette Vera, Scheller, Jürgen, Piekorz, Roland P., Reichert, Andreas S., Volleth, Marianne, Wolf, Matthew J., Cirstea, Ion Cristian, Gelb, Bruce D., Tartaglia, Marco, Schmitt, Joachim P., Krüger, Martina, Kutschka, Ingo, Cyganek, Lukas, Zenker, Martin, Kensah, George, Ahmadian, Mohammad R.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 21.06.2023; Nature Publishing Group; Nature Portfolio
• Subjects: 101/1; 13; 14; 38; 42; 631/80/86/2368; 692/4019/2773; 82; 96; Biology; Biomedical and Life Sciences; Biopsy; Calcium (intracellular); Calcium signalling; Cardiomyocytes; Cardiomyopathy; Cardiomyopathy, Hypertrophic - genetics; Cardiomyopathy, Hypertrophic - metabolism; Cardiomyopathy, Hypertrophic - pathology; Connectin; Genotypes; Germ-Line Mutation; Heart diseases; Humans; Intracellular signalling; Life Sciences; MAP kinase; Muscle contraction; Myocytes, Cardiac - metabolism; Noonan Syndrome - complications; Noonan Syndrome - genetics; Noonan Syndrome - metabolism; Noonan's syndrome; Phenotypes; Pluripotency; Proto-Oncogene Proteins c-raf - genetics; Signal Transduction; Stem cells; Structure-function relationships
• ISSN: 2399-3642; 2399-3642
• DOI: 10.1038/s42003-023-05013-8

Noonan syndrome (NS), the most common among RASopathies, is caused by germline variants in genes encoding components of the RAS-MAPK pathway. Distinct variants, including the recurrent Ser257Leu substitution in RAF1, are associated with severe hypertrophic cardiomyopathy (HCM). Here, we investigated the elusive mechanistic link between NS-associated RAF1 S257L and HCM using three-dimensional cardiac bodies and bioartificial cardiac tissues generated from patient-derived induced pluripotent stem cells (iPSCs) harboring the pathogenic RAF1 c.770 C > T missense change. We characterize the molecular, structural, and functional consequences of aberrant RAF1–associated signaling on the cardiac models. Ultrastructural assessment of the sarcomere revealed a shortening of the I-bands along the Z disc area in both iPSC-derived RAF1 S257L cardiomyocytes and myocardial tissue biopsies. The aforementioned changes correlated with the isoform shift of titin from a longer (N2BA) to a shorter isoform (N2B) that also affected the active force generation and contractile tensions. The genotype-phenotype correlation was confirmed using cardiomyocyte progeny of an isogenic gene-corrected RAF1 S257L -iPSC line and was mainly reversed by MEK inhibition. Collectively, our findings uncovered a direct link between a RASopathy gene variant and the abnormal sarcomere structure resulting in a cardiac dysfunction that remarkably recapitulates the human disease. Studies on 3D bioartificial cardiac tissues reveal the impacts of hypertrophic cardiomyopathy-associated RAF1 mutations on sarcomere structure, contractile behavior, Ca 2+ handling, and intracellular signaling.