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Abnormal nuclear shape and impaired mechanotransduction in emerin-deficient cells.

Lammerding J, Hsiao J, Schulze PC, Kozlov S, Stewart CL, Lee RT - J. Cell Biol. (2005)

Bottom Line: Clin.Invest. 113:370-378).Thus, emerin-deficient mouse embryo fibroblasts have apparently normal nuclear mechanics but impaired expression of mechanosensitive genes in response to strain, suggesting that emerin mutations may act through altered transcriptional regulation and not by increasing nuclear fragility.

View Article: PubMed Central - PubMed

Affiliation: Cardiovascular Division, Brigham and Women's Hospital, Boston, MA 02115, USA. jlammerding@rics.bwh.harvard.edu

ABSTRACT
Emery-Dreifuss muscular dystrophy can be caused by mutations in the nuclear envelope proteins lamin A/C and emerin. We recently demonstrated that A-type lamin-deficient cells have impaired nuclear mechanics and altered mechanotransduction, suggesting two potential disease mechanisms (Lammerding, J., P.C. Schulze, T. Takahashi, S. Kozlov, T. Sullivan, R.D. Kamm, C.L. Stewart, and R.T. Lee. 2004. J. Clin. Invest. 113:370-378). Here, we examined the function of emerin on nuclear mechanics and strain-induced signaling. Emerin-deficient mouse embryo fibroblasts have abnormal nuclear shape, but in contrast to A-type lamin-deficient cells, exhibit nuclear deformations comparable to wild-type cells in cellular strain experiments, and the integrity of emerin-deficient nuclear envelopes appeared normal in a nuclear microinjection assay. Interestingly, expression of mechanosensitive genes in response to mechanical strain was impaired in emerin-deficient cells, and prolonged mechanical stimulation increased apoptosis in emerin-deficient cells. Thus, emerin-deficient mouse embryo fibroblasts have apparently normal nuclear mechanics but impaired expression of mechanosensitive genes in response to strain, suggesting that emerin mutations may act through altered transcriptional regulation and not by increasing nuclear fragility.

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Characterization of emerin  fibroblasts. (a) Western analysis of homozygous (−/− and −/Y) and heterozygous (+/−) emerin  and wild-type (+/+ and +/Y) adult muscle fibroblasts, showing a complete lack of emerin in the homozygous cells. Protein expression of lamin A/C and lamin B1 appeared normal in the emerin  homozygous and heterozygous cells. (b) Female heterozygous (i.e., Emd+/−) muscle fibroblasts stained with anti-emerin antibody (left) and DAPI (right). Two cells (*) clearly lack emerin staining (as visualized by comparing with the DAPI staining), reflecting the differential X-chromosome inactivation in the heterozygous cell population.
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fig1: Characterization of emerin fibroblasts. (a) Western analysis of homozygous (−/− and −/Y) and heterozygous (+/−) emerin and wild-type (+/+ and +/Y) adult muscle fibroblasts, showing a complete lack of emerin in the homozygous cells. Protein expression of lamin A/C and lamin B1 appeared normal in the emerin homozygous and heterozygous cells. (b) Female heterozygous (i.e., Emd+/−) muscle fibroblasts stained with anti-emerin antibody (left) and DAPI (right). Two cells (*) clearly lack emerin staining (as visualized by comparing with the DAPI staining), reflecting the differential X-chromosome inactivation in the heterozygous cell population.

Mentions: Emerin-deficient mouse embryo fibroblasts were derived from male emerin hemizygous mice (Emd−/y) and have been shown to lack emerin expression (unpublished data). Emerin-deficient mice were derived by deletion of the entire coding region of the Emd gene, which resulted in the complete absence of emerin protein as shown by Western and immunohistochemical analysis of muscle fibroblasts isolated from the mice (Fig. 1). The Emd mice (both −/y males and −/− females) showed no overt pathology in either their skeletal or cardiac muscle, even in mice as old as 12–15 mo (unpublished data). Hereafter we have focused our studies on analyzing Emd−/y fibroblasts derived from male embryos to avoid possible heterogeneity due to X-chromosome–associated gene dosage compensation effects in cell lines of female origin.


Abnormal nuclear shape and impaired mechanotransduction in emerin-deficient cells.

Lammerding J, Hsiao J, Schulze PC, Kozlov S, Stewart CL, Lee RT - J. Cell Biol. (2005)

Characterization of emerin  fibroblasts. (a) Western analysis of homozygous (−/− and −/Y) and heterozygous (+/−) emerin  and wild-type (+/+ and +/Y) adult muscle fibroblasts, showing a complete lack of emerin in the homozygous cells. Protein expression of lamin A/C and lamin B1 appeared normal in the emerin  homozygous and heterozygous cells. (b) Female heterozygous (i.e., Emd+/−) muscle fibroblasts stained with anti-emerin antibody (left) and DAPI (right). Two cells (*) clearly lack emerin staining (as visualized by comparing with the DAPI staining), reflecting the differential X-chromosome inactivation in the heterozygous cell population.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2171355&req=5

fig1: Characterization of emerin fibroblasts. (a) Western analysis of homozygous (−/− and −/Y) and heterozygous (+/−) emerin and wild-type (+/+ and +/Y) adult muscle fibroblasts, showing a complete lack of emerin in the homozygous cells. Protein expression of lamin A/C and lamin B1 appeared normal in the emerin homozygous and heterozygous cells. (b) Female heterozygous (i.e., Emd+/−) muscle fibroblasts stained with anti-emerin antibody (left) and DAPI (right). Two cells (*) clearly lack emerin staining (as visualized by comparing with the DAPI staining), reflecting the differential X-chromosome inactivation in the heterozygous cell population.
Mentions: Emerin-deficient mouse embryo fibroblasts were derived from male emerin hemizygous mice (Emd−/y) and have been shown to lack emerin expression (unpublished data). Emerin-deficient mice were derived by deletion of the entire coding region of the Emd gene, which resulted in the complete absence of emerin protein as shown by Western and immunohistochemical analysis of muscle fibroblasts isolated from the mice (Fig. 1). The Emd mice (both −/y males and −/− females) showed no overt pathology in either their skeletal or cardiac muscle, even in mice as old as 12–15 mo (unpublished data). Hereafter we have focused our studies on analyzing Emd−/y fibroblasts derived from male embryos to avoid possible heterogeneity due to X-chromosome–associated gene dosage compensation effects in cell lines of female origin.

Bottom Line: Clin.Invest. 113:370-378).Thus, emerin-deficient mouse embryo fibroblasts have apparently normal nuclear mechanics but impaired expression of mechanosensitive genes in response to strain, suggesting that emerin mutations may act through altered transcriptional regulation and not by increasing nuclear fragility.

View Article: PubMed Central - PubMed

Affiliation: Cardiovascular Division, Brigham and Women's Hospital, Boston, MA 02115, USA. jlammerding@rics.bwh.harvard.edu

ABSTRACT
Emery-Dreifuss muscular dystrophy can be caused by mutations in the nuclear envelope proteins lamin A/C and emerin. We recently demonstrated that A-type lamin-deficient cells have impaired nuclear mechanics and altered mechanotransduction, suggesting two potential disease mechanisms (Lammerding, J., P.C. Schulze, T. Takahashi, S. Kozlov, T. Sullivan, R.D. Kamm, C.L. Stewart, and R.T. Lee. 2004. J. Clin. Invest. 113:370-378). Here, we examined the function of emerin on nuclear mechanics and strain-induced signaling. Emerin-deficient mouse embryo fibroblasts have abnormal nuclear shape, but in contrast to A-type lamin-deficient cells, exhibit nuclear deformations comparable to wild-type cells in cellular strain experiments, and the integrity of emerin-deficient nuclear envelopes appeared normal in a nuclear microinjection assay. Interestingly, expression of mechanosensitive genes in response to mechanical strain was impaired in emerin-deficient cells, and prolonged mechanical stimulation increased apoptosis in emerin-deficient cells. Thus, emerin-deficient mouse embryo fibroblasts have apparently normal nuclear mechanics but impaired expression of mechanosensitive genes in response to strain, suggesting that emerin mutations may act through altered transcriptional regulation and not by increasing nuclear fragility.

Show MeSH
Related in: MedlinePlus