Both proteins are required for nuclear organization and cell proliferation in dividing germ line and somatic cells, and to maintain the expression of at least one gene (hlh-8). to the larval L2 stage, then arrested. Nondividing somatic cell nuclei appeared Rabbit polyclonal to Noggin normal, whereas dividing cells had abnormal nuclear envelope and chromatin organization and severe defects in postembryonic cell divisions, including the mesodermal lineage. Life span was unaffected by loss of Ce-emerin alone but was significantly reduced in LEM-2null animals, and double-null animals had an even shorter life span. In addition to striated muscle defects, double-null animals and LEM-2null animals showed unexpected defects in smooth muscle activity. These findings implicate human LEM2 mutations as a potential cause of EDMD and further suggest human LEM2 mutations might cause distinct disorders of greater severity, sinceC. eleganslacking only LEM-2 had significantly reduced life span and smooth muscle activity. == Ferroquine INTRODUCTION == The nuclear envelope (NE) has two membranes (inner and outer nuclear membranes [INM and ONM, respectively]) and nuclear pore complexes (NPCs) that mediate traffic between the nucleus and cytoplasm (Gruenbaumet al., 2005;Stewartet al., 2007). The NE and its lumen are continuous with the endoplasmic reticulum (ER) and share many ER functions. However, the INM and ONM are also specifically enriched for distinct integral membrane proteins (Schirmer and Gerace, Ferroquine 2005;Maliket al., 2010). The mammalian INM has more than 50 distinct membrane Ferroquine proteins (Wilson and Berk, 2010), most of which are uncharacterized. Among the characterized INM proteins, most can bind directly to nuclear intermediate filaments formed by A- or B-type lamin proteins (Dechatet al., 2008). Lamins are major components of Ferroquine the nucleoskeleton (Simon and Wilson, 2011). One prominent family of lamin-binding proteins shares the LAP2, emerin, MAN1 (LEM) domain, an 45-residue folded motif (Laguriet al., 2001). Most LEM-domain proteins are located at the INM. The LEM domain binds a conserved metazoan chromatin protein named barrier-to-autointegration factor (BAF). BAF is a mobile lamin-binding protein that can bridge double-stranded DNA (dsDNA); BAF also binds histones (Montes de Ocaet al., 2005,2009;Margalitet al., 2007a) and influences many specific histone posttranslational modifications (Montes de Ocaet al., 2011). Mammals have four characterized LEM genes encoding LAP2 (, , and other isoforms), MAN1, emerin, and LEM2/NET25, and three uncharacterized genes (ANKLE1,ANKLE2,LEMD1) encoding predicted proteins also known as LEM3, LEM4, and LEM5, respectively (Wagner and Krohne, 2007;Wilson and Foisner, 2010). Mutations in emerin cause recessive X-linked Emery-Dreifuss muscular dystrophy (X-EDMD;Bioneet al., 1994), which is characterized by weakening of specific skeletal muscles, contractures, cardiomyopathy, and cardiac Ferroquine conduction system defects that can cause sudden death (Muchir and Worman, 2007). EDMD can also be caused by dominant mutations in the genes encoding A-type lamins (LMNA), nesprin-1 proteins (SYNE-1), or nesprin-2 proteins (SYNE-2;Haqueet al., 2010;Wheeler and Ellis, 2010). Emerin binds directly to products of all three genes, and its localization at the INM in somatic mammalian cells requires A-type lamins (Mislowet al., 2002;Zhanget al., 2005;D’Angelo and Hetzer, 2006). Emerin also associates directly or indirectly with the conserved INM protein LUMA, encoded by a fifth gene linked to EDMD (TMEM43;Lianget al., 2011). Specific mutations in a sixth gene (four-and-a-half LIM domains 1 [FHL1]) encoding a transcription factor relevant to muscle mass also cause muscular disorders, including EDMD (Gueneauet al., 2009). TheC. elegansgenome has only three LEM-domain genes:emr-1(encoding Ce-emerin protein),lem-2(encoding LEM-2, previously termed Ce-MAN1), andlem-3. The protein encoded bylem-3has no transmembrane domain and is uncharacterized. Ce-emerin and LEM-2 are INM proteins expressed in essentially all cells duringC. elegansdevelopment (Leeet al., 2000). They have similar biochemical properties: both bind Ce-lamin, both require Ce-lamin for their nuclear envelope localization (Gruenbaumet al., 2002;Liuet al., 2003), and both bind directly to BAF-1 (Liuet al., 2003). Thus Ce-emerin and LEM-2 are the only membrane-integral LEM-domain proteins inC. elegans, and their known properties are similar to human emerin and LEM2. LEM-2 and Ce-emerin possess overlapping features inC. elegansearly embryos, since neither gene (emr-1orlem-2) only is vital (Gruenbaumet al., 2002;Liuet al., 2003), but RNA disturbance (RNAi)-mediated down-regulation of both genes can be synthetically lethal to early embryos, with loss of life in the 100-cell stage (Liuet al., 2003). Mammalian emerin and LEM2 possess overlapping features in the rules of extracellular also, signal-regulated kinase signaling in developing myoblasts (Huberet al.,.