Characterization of osteoporosis in a patient with Werner's syndrome

Werner syndrome (WRN) gene variants and their association with altered function and age-associated diseases

Werner syndrome (WS) is a heritable autosomal recessive human disorder characterized by the premature onset of several age-associated pathologies including cancer. The protein defective in WS patients, WRN, is encoded by a member of the human RECQ gene family that contains both a DNA exonuclease and a helicase domain. WRN has been shown to participate in several DNA metabolic pathways including DNA replication, recombination and repair, as well as telomere maintenance and transcription modulation. Here we review base pair-level genetic variation that has been documented in WRN, with an emphasis on non-synonymous coding single nucleotide polymorphisms (SNPs) and their associations with anthropomorphic features, longevity and disease risk. These associations have been challenging to identify, as many reported WRN SNP associations appear to be further conditioned upon ethnic, age, gender or other environmental co-variables. The WRN variant phenotypic associations identified to date are intriguing, and several are of clear clinical import. Consequently, it will be important to extend these initial associations and to identify the mechanisms and conditions under which specific WRN variants may compromise WRN function to drive cellular and organismal phenotypes as well as disease risk.

A missense single nucleotide polymorphism, V114I of the Werner syndrome gene, is associated with risk of osteoporosis and femoral fracture in the Japanese population

Werner syndrome is a rare autosomal recessive disorder caused by mutations in the human WRN gene and characterized by the early onset of normal aging symptoms. Given that patients with this disease exhibit osteoporosis, the present study aimed to determine whether the WRN gene contributes to the etiology of osteoporosis. A genetic association study of eight non-synonymous polymorphisms in the WRN gene and the incidence of femoral fracture was undertaken in 1,632 consecutive Japanese autopsies in which 140 patients had experienced the fracture during their lifetime. The results were validated in 251 unrelated postmenopausal Japanese women with osteoporosis and 269 non-institutionalized, community-dwelling Japanese adults. A statistically significant association was observed between rs2230009 (c.340G > A)--which results in a Val to Ile substitution--and fracture risk; the incidence of femoral fracture increased dose-dependently with the number of A alleles (p = 0.0120). Femoral neck bone and whole bone densities were lower among postmenopausal women with osteoporosis and community-dwelling adults, respectively, if they were of the AG instead of the GG genotype. The results suggest that Japanese subjects bearing at least one A allele of rs2230009 of the WRN gene are at a significantly higher risk of femoral fracture, possibly due to decreased bone density.

Werner Syndrome-specific induced pluripotent stem cells: recovery of telomere function by reprogramming

Werner syndrome (WS) is a rare human autosomal recessive premature aging disorder characterized by early onset of aging-associated diseases, chromosomal instability, and cancer predisposition. The function of the DNA helicase encoded by WRN, the gene responsible for WS, has been studied extensively. WRN helicase is involved in the maintenance of chromosome integrity through DNA replication, repair, and recombination by interacting with a variety of proteins associated with DNA repair and telomere maintenance. The accelerated aging associated with WS is reportedly caused by telomere dysfunction, and the underlying mechanism of the disease is yet to be elucidated. Although it was reported that the life expectancy for patients with WS has improved over the last two decades, definitive therapy for these patients has not seen much development. Severe symptoms of the disease, such as leg ulcers, cause a significant decline in the quality of life in patients with WS. Therefore, the establishment of new therapeutic strategies for the disease is of utmost importance. Induced pluripotent stem cells (iPSCs) can be established by the introduction of several pluripotency genes, including Oct3/4, Sox2, Klf4, and c-myc into differentiated cells. iPSCs have the potential to differentiate into a variety of cell types that constitute the human body, and possess infinite proliferative capacity. Recent studies have reported the generation of iPSCs from the cells of patients with WS, and they have concluded that reprogramming represses premature senescence phenotypes in these cells. In this review, we summarize the findings of WS patient-specific iPSCs (WS iPSCs) and focus on the roles of telomere and telomerase in the maintenance of these cells. Finally, we discuss the potential use of WS iPSCs for clinical applications.

Reprogramming suppresses premature senescence phenotypes of Werner syndrome cells and maintains chromosomal stability over long-term culture

Werner syndrome (WS) is a premature aging disorder characterized by chromosomal instability and cancer predisposition. Mutations in WRN are responsible for the disease and cause telomere dysfunction, resulting in accelerated aging. Recent studies have revealed that cells from WS patients can be successfully reprogrammed into induced pluripotent stem cells (iPSCs). In the present study, we describe the effects of long-term culture on WS iPSCs, which acquired and maintained infinite proliferative potential for self-renewal over 2 years. After long-term cultures, WS iPSCs exhibited stable undifferentiated states and differentiation capacity, and premature upregulation of senescence-associated genes in WS cells was completely suppressed in WS iPSCs despite WRN deficiency. WS iPSCs also showed recapitulation of the phenotypes during differentiation. Furthermore, karyotype analysis indicated that WS iPSCs were stable, and half of the descendant clones had chromosomal profiles that were similar to those of parental cells. These unexpected properties might be achieved by induced expression of endogenous telomerase gene during reprogramming, which trigger telomerase reactivation leading to suppression of both replicative senescence and telomere dysfunction in WS cells. These findings demonstrated that reprogramming suppressed premature senescence phenotypes in WS cells and WS iPSCs could lead to chromosomal stability over the long term. WS iPSCs will provide opportunities to identify affected lineages in WS and to develop a new strategy for the treatment of WS.

The clinical characteristics of Werner syndrome: molecular and biochemical diagnosis

Werner syndrome (WS) is an adult onset segmental progeroid syndrome caused by mutations in the WRN gene. The WRN gene encodes a 180 kDa nuclear protein that possesses helicase and exonuclease activities. The absence of WRN protein leads to abnormalities in various DNA metabolic pathways such as DNA repair, replication and telomere maintenance. Individuals with WS generally develop normally until the third decade of life, when premature aging phenotypes and a series of age-related disorders begin to manifest. In Japan, where a founder effect has been described, the frequency of Werner heterozygotes appears to be as high as 1/180 in the general population. Due to the relatively non-specific nature of the symptoms and the lack of awareness of the condition, this disease may be under-diagnosed in other parts of the world. Genetic counseling of WS patients follows the path of other autosomal recessive disorders, with special attention needed for cancer surveillance in relatives. Molecular diagnosis of WS is made by nucleotide sequencing and, in some cases, protein analysis. It is also of potential interest to measure WRN activities in WS patients. More than 50 different disease-causing mutations in the WRN gene have been identified in WS patients from all over the world. All but one of these cases has mutations that result in the premature termination of the protein. Here we describe the clinical, molecular and biochemical characteristics of WS for use by medical professionals in a health care setting. Additional information is available through the International Registry of WS (http://www.wernersyndrome.org).

Soft-tissue mineralization in Werner syndrome

Werner syndrome is a rare autosomal recessive disorder characterized by clinical signs of premature aging, short stature, scleroderma-like skin changes, endocrine abnormalities, cataracts, and an increased incidence of malignancies. We report on a 48-year-old woman with Werner syndrome associated with intracranial meningiomas who had extensive musculoskeletal manifestations including osteoporosis of the extremities, extensive tendinopathy about the ankles, osteomyelitis of the phalanges of the first left toe, abundant soft-tissue calcification, and two dense ossified soft-tissue masses, with cortical bone and trabeculae arising from the posterosuperior aspect of the calcanei and extending into Kager fat pads. A review of previous descriptions of the radiological abnormalities of Werner syndrome indicates that the presence of soft-tissue calcifications has either not been noted or been mentioned only briefly. Moreover, there is no mention of bony masses associated with Werner syndrome in the world literature, and this would appear to be the first report of this kind.

Werner Syndrome

Werner syndrome is a premature aging disease caused by the mutation in the WRN gene. The cloning and characterization of the WRN gene and its product allows investigators to study the disease and the human aging process at molecular level. This review summarizes the recent progresses on various aspects of the WRN research including functional analysis of the protein, interactive cloning, complexes formation, mouse models, and SNPs (single nucleotide polymorphisms). These in depth investigations have greatly advanced our understanding of the disease and elucidated future research direction for Werner syndrome and the human aging process.

Effect of age and apoptosis on the mouse homologue of the huWRN gene

Werner's syndrome (WS) is an inherited disease with clinical symptoms which resemble premature aging. The Werner's syndrome gene (WRN), which is located on human chromosome 8p12, encodes a predicted protein of 1432 amino acids and shows significant similarity to DNA helicases. We have cloned the full-length mouse cDNA homologue of the human WRN gene encoding a predicted protein of 1320 amino acids and have obtained a full-length 70 kb genomic clone containing the moWRN gene. This gene has been mapped to chromosome 8A3 in mice. The expression of the moWRN gene was increased during apoptosis after IL-2 deprivation, and decreased in the spleen of aged mice. Lymphoid cells isolated from a patient with WS exhibited increased apoptosis after incubation with anti-Fas but not after incubation with the topoisomerase inhibitor VP16. RNase protection reviled dysregulation of the ICE family of apoptosis molecules in the WS cell line. These results indicate that the WS helicase is involved in certain pathways of apoptosis, and defective WS gene expression leads to accumulation of cells that are highly susceptibility to Fas-induced apoptosis.

Twenty-four hour growth hormone secretion in a patient with Werner's syndrome

OBJECTIVE

To assess the 24-h endogenous secretory growth hormone (GH) profile and serum insulin-like growth factor-I (IGF-I) response to exogenous recombinant human growth hormone (rhGH) in a patient with Werner's syndrome.

DESIGN

Blood sampling every 20 min for 24 h followed by three daily injections of growth hormone.

SETTING

General Clinical Research Center.

PATIENTS

Single patient with Werner's syndrome.

MEASUREMENTS

Serum GH and IGF-I.

RESULTS

Growth hormone pulses were absent during the 24-h monitoring period. Likewise, integrated GH concentrations were very low at 0.25 mu min/mL, and no peaks occurred after sleep onset. Following single daily administration of rhGH, serum GH and IGF-I rose.

CONCLUSIONS

Our findings support previous but less extensive studies suggesting patients with Werner's syndrome have reduced growth hormone levels. Preliminary investigations using rhGH in patients with Werner's syndrome should be considered.

Potential for pharmacological intervention in Werner syndrome

Werner syndrome is a rare genetic disease of premature aging which manifests itself in the form of a variety of aging-like phenomena and diseases. It is an appropriate target for aging research because it is clear that the complications must be caused by one original gene defect. Another reason why this disease is of particular interest is observed at the cellular level. The abbreviated lifespan of cultured fibroblasts from patients with this disorder parallels the clinical features of this accelerated aging disease. Recent studies have met with some success in identifying certain genes involved in Werner syndrome and the roles they might play in normal cellular senescence. Such advances might result in a therapeutic breakthrough for this essentially incurable genetic disease. In addition, such a treatment might find some application in the control of the normal aging process.