Hutchinson-Gilford progeria syndrome (HGPS, OMIM 176670) is a rare disorder characterized by accelerated aging and early death, frequently from stroke or coronary artery disease. 90% of HGPS cases carry the LMNA G608G (GGC>GGT) mutation within exon 11 of LMNA, activating a splice donor site that results in production of a dominant negative form of lamin A protein, denoted progerin. Screening 150 skin biopsies from unaffected individuals (newborn to 97 years) showed that a similar splicing event occurs in vivo at a low level in the skin at all ages. While progerin mRNA remains low, the protein accumulates in the skin with age in a subset of dermal fibroblasts and in a few terminally differentiated keratinocytes. Progerin-positive fibroblasts localize near the basement membrane and in the papillary dermis of young adult skin; however, their numbers increase and their distribution reaches the deep reticular dermis in elderly skin. Our findings demonstrate that progerin expression is a biomarker of normal cellular aging and may potentially be linked to terminal differentiation and senescence in elderly individuals.

Hutchinson-Gilford progeria syndrome (HGPS; Online Mendelian Inheritance in Man accession no. 176670) is a rare disorder that is characterized by segmental premature aging and death between 7 and 20 years of age from severe premature atherosclerosis. Mutations in the LMNA gene are responsible for this syndrome. Approximately 80% of HGPS cases are caused by a G608 (GGC3 GGT) mutation within exon 11 of LMNA, which elicits a deletion of 50 aa near the C terminus of prelamin A. In this article, we present evidence that the mutant lamin A (progerin) accumulates in the nucleus in a cellular age-dependent manner. In human HGPS fibroblast cultures, we observed, concomitantly to nuclear progerin accumulation, severe nuclear envelope deformations and invaginations preventable by farnesyltransferase inhibition. Nuclear alterations affect cell-cycle progression and cell migration and elicit premature senescence. Strikingly, skin biopsy sections from a subject with HGPS showed that the truncated lamin A accumulates primarily in the nuclei of vascular cells. This finding suggests that accumulation of progerin is directly involved in vascular disease in progeria.aging ͉ atherosclerosis H utchinson-Gilford progeria syndrome (HGPS) is a rare, fatal genetic disorder that is characterized by accelerated aging in children. The LMNA gene encoding the A-type lamins A and C is the causative gene of HGPS (1-3). Approximately 80% of HGPS cases carry the heterozygous silent point mutation G608G within exon 11 of LMNA (3). This mutation creates an abnormal splice donor site, which produces a truncated protein (progerin) lacking residues 607-656 of prelamin A but retaining the C-terminal CAAX box, a target for prenylation (1-3).The nuclear lamina is a scaffold, which provides structural and mechanical stability for the nuclear envelope (NE); it consists primarily of type V intermediate filament proteins (A-and B-type lamins) and many inner-nuclear membrane proteins (4-7). Lamins interact with heterochromatin and transcriptional regulators, suggesting their important role in the maintenance of chromatin organization and gene expression (8).At the NE periphery, lamin precursors undergo a series of posttranslational modifications. B-type lamins are permanently isoprenylated, whereas prelamin A loses its modification after incorporation into the lamina by lamin A-specific processing steps involving Zmpste24 endoprotease (9-11). Because the endoproteolytic cleavage site is lost in the truncated lamin A (progerin), it was predicted to be permanently prenylated (3). Direct and indirect analyses have recently confirmed that progerin retains the farnesyl group (12)(13)(14)(15).Previous studies of A-type lamin distribution in primary dermal fibroblasts from HGPS patients showed nuclear abnormalities in size and shape in a subpopulation of cells in culture (3,16,17). Farnesylated progerin appears to be responsible for the nuclear deformations because administration of farnesyltransferase inhibitors to the HGPS fibroblast cultures normalized the nucle...

Hutchinson-Gilford Progeria Syndrome (HGPS) is a rare premature aging disorder caused by a de novo heterozygous point mutation G608G (GGC>GGT) within exon 11 of LMNA gene encoding A-type nuclear lamins. This mutation elicits an internal deletion of 50 amino acids in the carboxyl-terminus of prelamin A. The truncated protein, progerin, retains a farnesylated cysteine at its carboxyl terminus, a modification involved in HGPS pathogenesis. Inhibition of protein farnesylation has been shown to improve abnormal nuclear morphology and phenotype in cellular and animal models of HGPS. We analyzed global gene expression changes in fibroblasts from human subjects with HGPS and found that a lamin A-Rb signaling network is a major defective regulatory axis. Treatment of fibroblasts with a protein farnesyltransferase inhibitor reversed the gene expression defects. Our study identifies Rb as a key factor in HGPS pathogenesis and suggests that its modulation could ameliorate premature aging and possibly complications of physiological aging.

Background: Hutchinson-Gilford progeria syndrome (HGPS, OMIM 176670) is a rare sporadic disorder with an incidence of approximately 1 per 8 million live births. The phenotypic appearance consists of short stature, sculptured nose, alopecia, prominent scalp veins, small face, loss of subcutaneous fat, faint mid-facial cyanosis, and dystrophic nails. HGPS is caused by mutations in LMNA, the gene that encodes nuclear lamins A and C. The most common mutation in subjects with HGPS is a de novo single-base pair substitution, G608G (GGC>GGT), within exon 11 of LMNA. This creates an abnormal splice donor site, leading to expression of a truncated protein.

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