Figure 5.

Detection of TNNI3K protein in ventricular tissue by immunohistochemistry. Immunohistochemistry was performed using three antibodies on ventricular tissue from four individuals. Column 1 illustrates cardiac tissue from an individual without DCM (non-DCM), Columns 2 and 3 illustrate cardiac tissue from individuals with genetically defined familial DCM due to mutations in TPM1 (TPM1 Mutant) or RBM20 (RBM20 Mutant), respectively. The fourth column illustrates cardiac tissue from individual III.4 who carries the G526D mutation in TNNI3K (TNNI3K Mutant). Antibodies that recognize (A) the N-terminus of TNNI3K or (B) the C-terminus of TNNI3K reveal markedly reduced TNNI3K protein expression in the sarcoplasm (A and B) and the nuclei (B) of cardiomyocytes in the individual with the G526D mutation as compared with control tissue. (C) In contrast, actin expression was retained in all individuals. (D) H&E staining demonstrated non-specific histopathologic changes, including cardiomyocyte hypertrophy (evidenced by enlargement of cardiomyocyte nuclei, arrowheads) and mild interstitial fibrosis (increased fibrous connective tissue between individual cardiomyocytes, arrows), although the degree of cardiomyocyte hypertrophy was only mild in the TNNI3K mutant, in contrast with the moderate-to-severe hypertrophy in the other three patients.