Defects in cell spreading and ERK1/2 activation in fibroblasts with lamin A/C mutations

Abstract

In-frame mutations in nuclear lamin A/C lead to a multitude of tissue-specific degenerative diseases known as the 'laminopathies'. Previous studies have demonstrated that lamin A/C-null mouse fibroblasts have defects in cell polarisation, suggesting a role for lamin A/C in nucleo-cytoskeletal-cell surface cross-talk. However, this has not been examined in patient fibroblasts expressing modified forms of lamin A/C. Here, we analysed skin fibroblasts from 3 patients with Emery-Dreifuss muscular dystrophy and from 1 with dilated cardiomyopathy. The emerin-lamin A/C interaction was impaired in each mutant cell line. Mutant cells exhibited enhanced cell proliferation, collagen-dependent adhesion, larger numbers of filopodia and smaller cell spread size, compared with control cells. Furthermore, cell migration, speed and polarization were elevated. Mutant cells also showed an enhanced ability to contract collagen gels at early time points, compared with control cells. Phosphotyrosine measurements during cell spreading indicated an initial temporal lag in ERK1/2 activation in our mutant cells, followed by hyper-activation of ERK1/2 at 2 h post cell attachment. Deregulated ERK1/2 activation is linked with cardiomyopathy, cell spreading and proliferation defects. We conclude that a functional emerin-lamin A/C complex is required for cell spreading and proliferation, possibly acting through ERK1/2 signalling.

Novel LMNA mutations in patients with Emery-Dreifuss muscular dystrophy and functional characterization of four LMNA mutations

“…Nuclear foci staining for lamin A are frequently described when over-expressing mutant and lamin A-wild type in vitro (Bechert, et al, 2003;Holt, et al, 2001;Ostlund, et al, 2001). In contrast, such foci are not very common in primary cells isolated from patients with LMNA mutations (Emerson, et al, 2009;Markiewicz, et al, 2002;Muchir, et al, 2004;Taimen, et al, 2009;Vigouroux, et al, 2001;Zhang, et al, 2007), suggesting that lamin A-positive foci formation can be (Capanni, et al, 2003;Muchir, et al, 2004). We see similar effects using mouse C2C12 myogenic cells.…”

Cellular micro-environments reveal defective mechanosensing responses and elevated YAP signaling in LMNA-mutated muscle precursors

“…There is growing evidence that the integrity of the nucleus (Lammerding et al, 2004;Lammerding et al, 2005;Hale et al, 2008) and mechanotransduction signaling (Lammerding et al, 2005;Emerson et al, 2009) might be impaired in the diseases linked to mutations in A-type lamins and lamin-associated proteins. Recent major findings from the Lammerding group show that cells and cardiac tissue from A-type lamin mutant mice have impaired nuclear translocation and downstream signaling of megakaryoblastic leukemia 1 protein (MKL1, also known as MRTF-A and MAL) (Ho et al, 2013), a transcription factor which regulates, through serum response factor (SRF), the expression of signaling molecules, transcription factors and numerous cytoskeletal components, including actin genes, nonmuscle myosins and vinculin (Schratt et al, 2002;Cen et al, 2003;Miralles et al, 2003).…”

Effects of exogenous ganglioside GM1 on different stages of cell spreading studied by directly quantifying spreading rate

“…Currently, there are mainly three morphometric approaches for quantitatively evaluating cell spreading based on various parameters of spread morphology: a) axial ratio (Xia et al, 2008;Emerson et al, 2009) or longest axis of spread cells (Knox, 1984;Shirai et al, 2011) (Figure 1b), mainly for spindle-shaped cells with long filopodia; b) percentage of spread cells (Vuori & Ruoslahti, 1993;Chae et al, 2010) (Figure 1a); c) spread area (Knox & Griffiths, 1980;Ezzell et al, 1997) (Figure 1c). The latter two methods, especially the second one, have been widely used.…”