Fig. 4: Aberrant RAF1^S257L activity impairs the cytoarchitecture of human iPSC-derived cardiomyocytes.

a Dissociated WT- and RAF1^S257L-CBs (line 1) were seeded on Geltrex-coated coverslips for 7 days and stained for cTNT and F-actin (Scale bar, 10 µm). b Representative EM images from RAF1^S257L-CBs revealed stronger myofibrillar disarray accompanied by shortened I-bands and a thickened Z-line pattern as compared to WT-CBs. c IHC analysis of RAF1^S257L cardiac tissues (CTs) from one of the NS individuals with RAF1 c.770 C>T variant for desmin and troponin showed myofilament disarray. d Representative EM images of the same RAF1^S257L-CTs as in C exhibited shortened I-bands and a thickened Z-line pattern consistent with RAF1^S257L-CBs in (b). e Quantification of the cell size area of the CB-EM pictures with image J software. *P < 0.05, unpaired 2-tailed t-test. n = 2. f Representative ICC images of RAF1^S257L and WT-CMs at d90 post-differentiation showed RAF1 co-localization with cTNT and F-actin at the sarcomere (Scale bar, 10 µm). g The quantifications of the organization and alignments of the sarcomeres in RAF1^S257L- and WT-CMs at d90 post-differentiation stained with anti-cTNT antibody, Fig. 3f, with Sota software. n = 2. h EM images of RAF1^S257L-CBs (d40) treated with 0.2 µM MEKi from d12 of differentiation.