Nuclear envelope alterations in fibroblasts from LGMD1B patients carrying nonsense Y259X heterozygous or homozygous mutation in lamin A/C gene Antoine Muchir, a Baziel G. van Engelen, b Martin Lammens, b John M. Mislow, c Elizabeth McNally, d Ketty Schwartz, a and Gise `le Bonne a, * a INSERM U582, Institut de Myologie, Groupe Hospitalier Pitie ´-Salpe ´trie `re, 75013 Paris, France b Institute of Neurology and Department of Pathology, Neuromuscular Centre Nijmegen, University Medical Centre Nijmegen, 6500 HB Nijmegen, The Netherlands c Department of Pathology, University of Chicago, Chicago, IL 60637, USA d Department of Medicine, University of Chicago, Chicago, IL 60637, USA Received 20 February 2003, revised version received 19 May 2003 Abstract Mutations in the LMNA gene encoding nuclear lamins A and C are responsible for seven inherited disorders affecting specific tissues. We have analyzed skin fibroblasts from a patient with type 1B limb-girdle muscular dystrophy and from her deceased newborn grandchild carrying, respectively, a heterozygous (+/mut) and a homozygous (mut/mut) nonsense Y259X mutation. In fibroblasts +/mut , the presence of only 50% lamins A and C promotes no detectable abnormality, whereas in fibroblasts mut/mut the complete absence of lamins A and C leads to abnormally shaped nuclei with lobules in which none of the analyzed nuclear proteins were detected, i.e., B-type lamins, emerin, nesprin-1, LAP2, and Nup153. These lobules perturb cell division as fibroblast mut/mut cultures with large proportions of cells with dysmorphic nuclei grow more slowly than controls and the cell proliferation normalizes when the number of these abnormally shaped nuclei declines. In all fibroblasts mut/mut , nesprin-1-like emerin exhibited aberrant localization in the endoplasmic reticulum. Transfection of wild-type lamin A or C cDNAs restored the correct localization of both emerin and nesprin-1. These data demonstrate that lamin C, like lamin A, interacts in vivo directly with nesprin-1 and with emerin and that lamin A or C is sufficient for the correct anchorage of emerin and nesprin-1 at the nuclear envelope in human cells. © 2003 Elsevier Inc. All rights reserved. Keywords: Lamins A and C; Emerin; Nesprin-1; Nuclear envelope; Nuclear lamina; Muscular dystrophy, LGMD1B Introduction Lamins are members of the intermediate filament protein family that form the nuclear lamina, a fibrous meshwork underlining the inner nuclear membrane (INM) of all eu- karyotic cells [1]. Two types of lamins have been identified in somatic cells, A-type and B-type. A-type lamins, A and C, are encoded by alternative splice of the LMNA gene, whereas B-type lamins, B1 and B2, are encoded by two genes [1]. While lamins B1 and B2, are found in all nucle- ated somatic cells, the expression of lamins A and C is developmentally regulated and their expression is restricted to differentiated nonproliferating cells [2,3]. Like all inter- mediate filament proteins, the lamins possess a long central -helical coil-coiled rod domain flanked by a short globular N-terminal head and a long C-terminal tail domain. The proteins form dimers via their rod domains, which then assemble to form the nuclear lamina [4]. The latter is at- tached to the INM via interactions with nuclear integral proteins. Among them, emerin, nesprin-1, and isoforms 1A, 1B, and 1C of the lamina-associated proteins (LAP) * Corresponding author: Inserm U582, Institut de Myologie, Ba ˆtiment Babinski, GH Pitie ´-Salpe ´trie `re, 47 boulevard de l’Ho ˆpital, 75651 Paris cedex 13, France. Fax: +33-1-42-16-57-00. E-mail address: g.bonne@myologie.chups.jussieu.fr (G. Bonne). R Available online at www.sciencedirect.com Experimental Cell Research 291 (2003) 352–362 www.elsevier.com/locate/yexcr 0014-4827/$ – see front matter © 2003 Elsevier Inc. All rights reserved. doi:10.1016/j.yexcr.2003.07.002