Defects in the biogenesis of lamin A from its farnesylated precursor, prelamin A, lead to the accumulation of prelamin A at the nuclear envelope, cause misshapen nuclei, and result in progeroid syndromes. A deficiency in ZMPSTE24, a protease involved in prelamin A processing, leads to prelamin A accumulation, an absence of mature lamin A, misshapen nuclei, and a lethal perinatal progeroid syndrome: restrictive dermopathy (RD). HutchinsonGilford progeria syndrome (HGPS) is caused by a mutant prelamin A that cannot be processed to lamin A. The hallmark cellular abnormality in RD and HGPS is misshapen nuclei. We hypothesized that the farnesylation of prelamin A is important for its targeting to the nuclear envelope in RD and HGPS and that blocking farnesylation would ameliorate the nuclear shape abnormalities. Indeed, when RD fibroblasts were treated with a farnesyltransferase inhibitor (FTI), prelamin A was partially mislocalized away from the nuclear envelope, and the frequency of nuclear shape abnormalities was reduced (P < 0.0001). A FTI also mislocalized prelamin A and improved nuclear shape in Zmpste24-deficient mouse embryonic fibroblasts (P < 0.0001) and improved nuclear shape in human HGPS fibroblasts (P < 0.0001). Most remarkably, a FTI significantly improved nuclear shape in two fibroblast cell lines from atypical progeria patients with lamin A missense mutations in the absence of prelamin A accumulation (P ‫؍‬ 0.0003 and P < 0.0001). These findings establish a paradigm for ameliorating the most obvious cellular pathology in lamin-related progeroid syndromes and suggest a potential strategy for treating these diseases.aging ͉ Hutchinson-Gilford progeria syndrome ͉ lamin ͉ restrictive dermopathy ͉ ZMPSTE24 T wo progerioid disorders in humans, restrictive dermopathy (RD) and Hutchinson-Gilford progeria syndrome (HGPS), are caused by defective biogenesis of lamin A from prelamin A, a farnesylated precursor protein (1-3). RD is a lethal perinatal progeroid disorder characterized by retarded growth, tight and rigid skin, alopecia, micrognathia, and other bone abnormalities. RD is caused by a deficiency in ZMPSTE24 (1, 2), a protease required for the endoproteolytic processing of prelamin A to mature lamin A (4, 5). HGPS is characterized by retarded growth, partial lipodystrophy, osteoporosis, osteolytic lesions, thin skin, micrognathia, and premature atherosclerosis (3). HGPS is caused by a mutant form of prelamin A (commonly called progerin) that cannot be processed to mature lamin A (3). Lamin A is a key protein within the nuclear lamina, an intermediate filament meshwork lining the inner nuclear membrane that provides structural support for the nucleus (6).Some progeroid syndromes are caused by missense mutations in LMNA (the gene for prelamin A and lamin C) (7,8). For example, E578V and R644C mutations cause progeroid disorders and are associated with nuclear shape abnormalities (8). In these cases, the structural abnormality in lamin A is apparently sufficient to impair nuclear envelope integrity and cau...

Abbreviations used in this paper: AChR, acetylcholine receptor; Bcam, basal cell adhesion molecule/Lutheran blood group antigen; BTX, ␣ -bungarotoxin; LG, laminin globular; MuSK, muscle-specifi c kinase; NMJ, neuromuscular junction.The online version of this article contains supplemental material.

Wrinkle-free (wrfr) is a previously uncharacterized, spontaneous, autosomal recessive mouse mutation resulting in very tight, thick skin. wrfr mutant mice exhibit severe breathing difficulties secondary to their tight skin and die shortly after birth. This phenotype is strikingly similar to a very rare human genetic disorder, restrictive dermopathy. wrfr mutant mice display a defective skin barrier, which is normally imparted by the cornified envelope, a composite of protein and lipid that prevents loss of water from within and entry of potentially harmful substances from without. In addition, hair growth from grafted wrfr skin is impaired. Positional cloning of the wrfr mutation revealed a retrotransposon insertion into a coding exon of Slc27a4, the gene encoding fatty acid transport protein (FATP)4. FATP4 is the primary intestinal FATP and is thought to play a major role in dietary fatty acid uptake; it therefore is viewed as a target to prevent or reverse obesity. However, its function in vivo had not been determined. Our results demonstrate an unexpected yet critical role for FATP4 in skin and hair development and suggest Slc27a4 to be a candidate gene for restrictive dermopathy.T he skin of mammals is composed of a dermis and an epidermis separated by a basement membrane. The epidermis is stratified, consisting of basal keratinocyte, spinous͞ prickle, granular, and squamous͞cornified layers. Keratinocytes move upward from the basement membrane and progress through a scheduled program of differentiation, with cell death marking their final differentiation step. During this differentiation program, keratinocytes flatten and accumulate lipids that are discharged into the intercellular space (1). In the stratum corneum the lipids are crosslinked with a number of proteins including loricrin and involucrin to form the cornified envelope (2). The insoluble cornified envelope is a composite of protein and lipid that serves as a barrier to loss of water from within and to entry of potentially harmful substances from without. Without such a barrier, life on land could not exist (3).We discovered a spontaneous, autosomal recessive mutation in our mouse colony causing extremely tight, thick skin. We named the mutation wrinkle-free (wrfr). The wrfr phenotype is similar to a rare human disease called restrictive dermopathy (4, 5). Newborn wrfr Ϫ͞Ϫ mice have difficulty breathing because of the tight skin, do not suckle, exhibit a defective skin barrier, and die several hours after birth. There are also defects in hair follicle morphogenesis and hair growth. Because of the presumed fundamental importance of the mutated gene to skin development and its potential relevance to human disease, we sought to identify the affected gene. Here we present a characterization of the wrfr phenotype and the positional cloning of the wrfr mutation. Materials and MethodsMicrosatellite Marker Analysis. Genomic DNA was prepared from tissues by standard proteinase K digestion, phenol͞chloroform extraction, and ethanol precipitation (6) or by ...

Restrictive dermopathy (RD) is a lethal human genetic disorder characterized by very tight, thin, easily eroded skin, rocker bottom feet, and joint contractures. This disease was recently reported to be associated with a single heterozygous mutation in ZMPSTE24 and hypothesized to be a digenic disorder (Navarro et al, Lamin A and ZMPSTE24 (FACE-1) defects cause nuclear disorganization and identify restrictive dermopathy as a lethal neonatal laminopathy. Hum Mol Genet 13:2493-2503, 2004). ZMPSTE24 encodes an enzyme necessary for the correct processing and maturation of lamin A, an intermediate filament component of the nuclear envelope. Here we present four unrelated patients with homozygous mutations in ZMPSTE24 and a fifth patient with compound heterozygous mutations in ZMPSTE24. Two of the three different mutations we found are novel, and all are single base insertions that result in messenger RNA frameshifts. As a consequence of the presumed lack of ZMPSTE24 activity, prelamin A, the unprocessed toxic form of lamin A, was detected in the nuclei of both cultured cells and tissue from RD patients, but not in control nuclei. Abnormally aggregated lamin A/C was also observed. These results indicate that RD is an autosomal recessive laminopathy caused by inactivating ZMPSTE24 mutations that result in defective processing and nuclear accumulation of prelamin A.