Figure 2: The Mutation p.L13R in LEMD2 Causes Interstitial Fibrosis and Abnormal Nuclei in Affected Myocardial Tissue and Fibroblasts

(A) Protein domain structure of human LEM domain containing protein 2 (LEMD2) and conserved motifs. (Top) the LEMD2 protein consists of an LEM domain, lamin A/C–binding domain, 2 transmembrane domains, and a Man1/Src1p C-terminal domain. Domain information was obtained from UniProt (63) and Brachner et al. (10). The red arrow indicates the location of the human mutation. (Bottom) The leucine residue at position 13 (yellow shadow) of LEMD2 is conserved across species. (B) Predicted 3-dimensional structure of the N-terminal domain of LEMD2 with wild-type leucine (Leu) in the left panel and the replaced arginine (Arg) at position 13 in the right. (C) Histology of cardiac tissue from patient 600, II-16 (Pat) showing extensive interstitial fibrosis and myocyte hypertrophy compared with the control (Ctrl). a, Masson’s trichrome (scale bar: 500 μm) staining shows fibrotic tissue in blue; b, hematoxylin and eosin staining (scale bar: 100 μm) and (c) picro sirius red (PSR) demonstrate collagen deposits (scale bar: 100 μm). Myocyte size in hematoxylin and eosin and collagen deposits in PSR were significantly increased in Pat vs. Ctrl; ***p < 0.001. (D) Representative images of affected myocardial tissue (upper panel) recorded by transmission electron microscopy revealed elongation and bizarre shapes/invagination of the membrane (arrowheads) of nuclei with clumping of peripheral heterochromatin (arrows). Transmission electron microscope images of fibroblasts (lower panel) from patient 600, II-18 (Pat) and age-matched control (Ctrl1). Note the abnormal morphology (arrowhead) of the nuclei and the condensed heterochromatin (arrows). (E) Quantification of abnormal nuclei in patient and age-matched control fibroblasts at passage 2 (P2) and passage 15 (P15); n = 300 nuclei, respectively. There is a significant increase of abnormal nuclei in the patient cells (Pat) compared with the control (Ctrl1); n = 300 nuclei; ***p < 0.001.