Optical coherence tomography findings in three patients with Werner syndrome

Background

Werner syndrome is a rare, autosomal recessive disorder characterised by premature aging. It is a typical hereditary progeroid syndrome that can be difficult to diagnose owing to its rarity and the similarity of some of its symptoms, such as juvenile cataracts, to other common ophthalmologic conditions. Early onset of bilateral cataracts is currently used as the ophthalmological feature for Werner syndrome; however, ophthalmologists often find performing a detailed examination of the medical history and genetic testing for Werner syndrome at the time of an ophthalmologic consultation challenging. If a unique ocular finding was observed on ocular examinations in cases of juvenile bilateral cataracts, we could consider Werner syndrome as a differential diagnosis. 

Case presentation

We documented the cases of three patients with Werner syndrome in whom thinning of the retina in the retinal nerve fiber layer (RNFL) and ganglion cell complex (GCC) were observed using optical coherence tomography (OCT). Visual field tests revealed the loss of visual field mainly owing to glaucoma.

The thinnig of the choroidal thickness (CT) in three patients was also observed using enhanced depth imaging (EDI)-OCT.

Conclusions

Three patients have thinning of the RNFL, GCC, and choroidal thickness and the loss of visual field. These findings suggest the need for including Werner syndrome in the differential diagnosis when patients presenting with juvenile cataracts of unknown cause also show abnormal retinal and choroidal thinning in the OCT images.

Skin ulcers associated with Werner syndrome: Prevention and non-surgical and surgical treatment

AIM

To provide guidelines on the diagnosis, treatment, and prevention of skin ulcers in Werner syndrome.

METHODS

This article was based on literature from 1996, when WRN was identified as a gene responsible for Werner syndrome, and we evaluated several authentic clinical cases of genetically diagnosed patients. There were 63 patients with Werner syndrome in the Japanese reports retrieved from Medical Online between January 1996 and December 2017. There were 56 patients with Werner syndrome in English reports written by Japanese authors and retrieved from PubMed during the same period.

RESULTS

Records on skin ulcers were found in 27 (43%) out of 63 patients and 22 (40%) out of 56 patients from the Japanese and English reports, respectively. The reported ulcers were often located at the distal one-third of the lower legs. There were 8 patients with callosities in the foot in the Japanese reports and 9 patients in the English reports. A skin ulcer in Werner syndrome is generally intractable. Weight-bearing ulcers or callosity should be critically assessed in surgical procedures because they have effects on patient pain and gait. By adopting a recently advanced technique to facilitate wound healing, the cases of ulcers that were difficult to treat and those requiring major operations can be closed with minimally invasive surgery.

CONCLUSIONS

Skin ulcers in Werner syndrome are refractory, and they lead to reduced quality of life of patients. A callosity in Werner syndrome is an important therapeutic target for the prevention of ulcers. Geriatr Gerontol Int 2021; 21: 153-159.

A Case Report of Werner's Syndrome With a Novel Mutation From India

Werner's syndrome (WS) or progeria adultorum is a heritable autosomal recessive disease in which the aging process is accelerated, just after puberty. It is caused by mutations in the WRN gene, which encodes a member of the RECQ family of DNA helicases and has a role in DNA repair. WS is being more appropriately recognized as a condition in which the lack of WRN protein results in an overall decline in the normal physiological functions of various organs rather than premature aging. Here, we describe a rare case of WS with a novel mutation from India. Our patient was an adult male with a history of growth arrest since puberty and other clinical features such as sclerodermatous skin changes, premature graying and thinning of hair, bilateral cataract, a single non-healing ulcer, hypothyroidism, underdeveloped secondary sexual characters with hypogonadism, infertility, squeaky voice, and early signs of arteriosclerosis. On genetic analysis, he was found to have a homozygous pathogenic variant c.3190C>T in exon 26 of the WRN gene, which has never been reported in WS.

Growing Old Too Fast: A Rare Case of Werner Syndrome

Werner syndrome (WS) is rare adult-onset progeria characterized by premature aging and early death. Patients develop normally until adolescence and usually present in early adulthood. Our case highlights a common presentation of this uncommon disease, wherein a 29-year-old non-obese male with no known risk factors developed uncontrolled diabetes, hypertriglyceridemia, and rapidly progressive atherosclerotic vascular disease. Careful observation with attention to the presence of characteristic physical features and subsequent genetic testing helped diagnose the patient with this uncommon progeroid syndrome. Our case adds to the literature about this rare disease especially in patients of middle-eastern descent and also highlights the importance of having a high index of suspicion for WS when the initial clinical presentation is atypical.

Characteristic Clinical Features of Werner Syndrome with a Novel Compound Heterozygous WRN Mutation c.1720+1G>A Plus c.3139-1G>C

Werner syndrome (WS) is an autosomal recessive progeroid disorder caused by mutations in the WRN gene (WRN). Most Japanese WS patients are born from a consanguineous marriage with homozygous WRN mutations. We herein report a rare WS patient born from non-consanguineous parents with compound heterozygous WRN mutations with a novel heterogeneous c.1720+1G>A substitution plus the most frequent heterogeneous c.3139-1G>C substitution among Japanese. Although the present case showed clinical characteristics common to previous Japanese WS patients, he had not developed any malignant tumors as of 43 years of age, suggesting that WS patients with this particular genetic mutation have a different phenotype than others.

Recurrent skin ulcer cross-repair and sensory reconstruction in a WRN gene mutational patient

A 37-year-old man complained of a refractory posterior malleolar ulceration on his left ankle. He was diagnosed with Werner syndrome according to the progeroid clinical features and genetic testing. To approach the ulceration, a free flow-through right anterolateral thigh perforator flap with anterolateral thigh cutaneous nerve was harvested. One year later, he was readmitted due to a new ulceration on his right ankle. We harvested the left anterolateral thigh perforator flap with anterolateral thigh cutaneous nerve to reconstruct the defect. After one more year of follow-up, there was no recurrence of ulcers, and the sensation of the flap recovered partially after 6 months. We conclude that free flow-through anterolateral thigh perforator flap is a feasible choice for the repair of foot ulcers in Werner syndrome.

Different non-synonymous polymorphisms modulate the interaction of the WRN protein to its protein partners and its enzymatic activities

Werner syndrome (WS) is characterized by the premature onset of several age-associated pathologies including cancer. The protein defective in WS patients (WRN) is a helicase/exonuclease involved in DNA replication and repair. Here, we present the results of a large-scale proteome analysis that has been undertaken to determine protein partners of different polymorphic WRN proteins found with relatively high prevalence in the human population. We expressed different fluorescently tagged-WRN (eYFP-WRN) variants in human 293 embryonic kidney cells (HEK293) and used a combination of affinity-purification and mass spectrometry to identify different compositions of WRN-associated protein complexes. We found that a WRN variant containing a phenylalanine residue at position 1074 and an arginine at position 1367 (eYFP-WRN(F-R)) possesses more affinity for DNA-PKc, KU86, KU70, and PARP1 than a variant containing a leucine at position 1074 and a cysteine at position 1367 (eYFP-WRN(L-C)). Such results were confirmed in a WRN-deficient background using WS fibroblasts. Interestingly, the exonuclase activity of WRN recovered from immunoprecipitated eYFP-WRN(L-C) variant was lower than the eYFP-WRN(F-R) in WS cells. Finally, HEK293 cells and WS fibroblasts overexpressing the eYFP-WRN(F-R) variant were more resistant to the benzene metabolite hydroquinone than cells expressing the eYFP-WRN(L-C) variant. These results indicate that the protein-protein interaction landscape of WRN is subject to modulation by polymorphic amino acids, a characteristic associated with distinctive cell survival outcome.

Should we treat aging as a disease? The consequences and dangers of miscategorisation

The aging of the population represents one of the largest healthcare challenges facing the world today. The available scientific evidence shows that interventions are available now that can target fundamental "aging" processes or pathways. Sufficient economic evidence is available to argue convincingly that this approach will also save enormous sums of money which could then be deployed to solve other urgent global problems. However, as yet this scenario has barely entered the public consciousness and, far from being a point of vigorous debate, seems to be ignored by policy makers. Understanding why this lethargy exists is important given the urgent need to deal with the challenge represented by population aging. In this paper I hypothesize that one major cause of inaction is a widely held, but flawed, conceptual framework concerning the relationship between aging and disease that categorizes the former as "natural" and the latter as "abnormal." This perspective is sufficient in itself to act as a disincentive to intervention by rendering those who hold it prone to the "naturalistic fallacy" but can give rise to active hostility to biogerontology if coupled with loose and/or blurred understanding of the goals and potential of the field.

Diabetes mellitus and cancer in Werner syndrome

Onishi et al. recently reported here an association of diabetes mellitus (DM) with neoplasm type in newly identified patients with Werner syndrome (WS), an autosomal recessive cancer predisposition syndrome with features of premature aging that include a high risk of DM (Onishi et al. in Acta Diabetol 49(Suppl 1):259-260, 2012; Epstein et al. in Medicine 45:177-121, 1966). In contrast, we did not detect an association between DM and neoplasm type in an independent WS cohort we assembled to determine the histopathologic spectrum and type-specific risk of neoplasia in WS.

The Drosophila orthologue of progeroid human WRN exonuclease, DmWRNexo, cleaves replication substrates but is inhibited by uracil or abasic sites : analysis of DmWRNexo activity in vitro

Werner syndrome (WS) is a rare late-onset premature ageing disease showing many of the phenotypes associated with normal ageing, and provides one of the best models for investigating cellular pathways that lead to normal ageing. WS is caused by mutation of WRN, which encodes a multifunctional DNA replication and repair helicase/exonuclease. To investigate the role of WRN protein's unique exonuclease domain, we have recently identified DmWRNexo, the fly orthologue of the exonuclease domain of human WRN. Here, we fully characterise DmWRNexo exonuclease activity in vitro, confirming 3'-5' polarity, demonstrating a requirement for Mg(2+), inhibition by ATP, and an ability to degrade both single-stranded DNA and duplex DNA substrates with 3' or 5' overhangs, or bubble structures, but with no activity on blunt ended DNA duplexes. We report a novel active site mutation that ablates enzyme activity. Lesional substrates containing uracil are partially cleaved by DmWRNexo, but the enzyme pauses on such substrates and is inhibited by abasic sites. These strong biochemical similarities to human WRN suggest that Drosophila can provide a valuable experimental system for analysing the importance of WRN exonuclease in cell and organismal ageing.

A role for the Werner syndrome protein in epigenetic inactivation of the pluripotency factor Oct4

Werner syndrome (WS) is an autosomal recessive disorder, the hallmarks of which are premature aging and early onset of neoplastic diseases (Orren, 2006; Bohr, 2008). The gene, whose mutation underlies the WS phenotype, is called WRN. The protein encoded by the WRN gene, WRNp, has DNA helicase activity (Gray et al., 1997; Orren, 2006; Bohr, 2008; Opresko, 2008). Extensive evidence suggests that WRNp plays a role in DNA replication and DNA repair (Chen et al., 2003; Hickson, 2003; Orren, 2006; Turaga et al., 2007; Bohr, 2008). However, WRNp function is not yet fully understood. In this study, we show that WRNp is involved in de novo DNA methylation of the promoter of the Oct4 gene, which encodes a crucial stem cell transcription factor. We demonstrate that WRNp localizes to the Oct4 promoter during retinoic acid-induced differentiation of human pluripotent cells and associates with the de novo methyltransferase Dnmt3b in the chromatin of differentiating pluripotent cells. Depletion of WRNp does not affect demethylation of lysine 4 of the histone H3 at the Oct4 promoter, nor methylation of lysine 9 of H3, but it blocks the recruitment of Dnmt3b to the promoter and results in the reduced methylation of CpG sites within the Oct4 promoter. The lack of DNA methylation was associated with continued, albeit greatly reduced, Oct4 expression in WRN-deficient, retinoic acid-treated cells, which resulted in attenuated differentiation. The presented results reveal a novel function of WRNp and demonstrate that WRNp controls a key step in pluripotent stem cell differentiation.

A role for WRN in telomere-based DNA damage responses

Telomeres cap the ends of eukaryotic chromosomes and prevent them from being recognized as DNA breaks. We have shown that certain DNA damage responses induced during senescence and, at times of telomere uncapping, also can be induced by treatment of cells with small DNA oligonucleotides homologous to the telomere 3' single-strand overhang (T-oligos), implicating this overhang in generation of these telomere-based damage responses. Here, we show that T-oligo-treated fibroblasts contain gammaH2AX foci and that these foci colocalize with telomeres. T-oligos with nuclease-resistant 3' ends are inactive, suggesting that a nuclease initiates T-oligo responses. We therefore examined WRN, a 3'-->5' exonuclease and helicase mutated in Werner syndrome, a disorder characterized by aberrant telomere maintenance, premature aging, chromosomal rearrangements, and predisposition to malignancy. Normal fibroblasts and U20S osteosarcoma cells rendered deficient in WRN showed reduced phosphorylation of p53 and histone H2AX in response to T-oligo treatment. Together, these data demonstrate a role for WRN in processing of telomeric DNA and subsequent activation of DNA damage responses. The T-oligo model helps define the role of WRN in telomere maintenance and initiation of DNA damage responses after telomere disruption.

The spectrum of WRN mutations in Werner syndrome patients

The International Registry of Werner syndrome (www.wernersyndrome.org) has been providing molecular diagnosis of the Werner syndrome (WS) for the past decade. The present communication summarizes, from among 99 WS subjects, the spectrum of 50 distinct mutations discovered by our group and by others since the WRN gene (also called RECQL2 or REQ3) was first cloned in 1996; 25 of these have not previously been published. All WRN mutations reported thus far have resulted in the elimination of the nuclear localization signal at the C-terminus of the protein, precluding functional interactions in the nucleus; thus, all could be classified as null mutations. We now report two new mutations in the N-terminus that result in instability of the WRN protein. Clinical data confirm that the most penetrant phenotype is bilateral ocular cataracts. Other cardinal signs were seen in more than 95% of the cases. The median age of death, previously reported to be in the range of 46-48 years, is 54 years. Lymphoblastoid cell lines (LCLs) have been cryopreserved from the majority of our index cases, including material from nuclear pedigrees. These, as well as inducible and complemented hTERT (catalytic subunit of human telomerase) immortalized skin fibroblast cell lines are available to qualified investigators.

DNA-related pathways defective in human premature aging

One of the major issues in studies on aging is the choice of biological model system. The human premature aging disorders represent excellent model systems for the study of the normal aging process, which occurs at a much earlier stage in life in these individuals than in normals. The patients with premature aging also get the age associated diseases at an early stage in life, and thus age associated disease can be studied as well. It is thus of great interest to understand the molecular pathology of these disorders.

Loss of Werner syndrome protein function promotes aberrant mitotic recombination

The chromosome 8p11-12 Werner syndrome (WRN ) locus encodes a RecQ helicase protein of unknown function that possesses both 3' --> 5' helicase and 3' --> 5' exonuclease activities. We show that WRN cell lines display a marked reduction in cell proliferation following mitotic recombination, and generate few viable gene conversion-type recombinants. These findings indicate that WRN plays a role in mitotic recombination, and that a loss of WRN function may promote genetic instability and disease via recombination-initiated mitotic arrest, cell death, or gene rearrangement.

Evidence for a replication function of FFA-1, the Xenopus orthologue of Werner syndrome protein

DNA replication in higher eukaryotic cells occurs at a large number of discrete sites called replication foci. We have previously purified a protein, focus-forming activity 1 (FFA-1), which is involved in the assembly of putative prereplication foci in Xenopus egg extracts. FFA-1 is the orthologue of the Werner syndrome gene product (WRN), a member of the RecQ helicase family. In this paper we show that FFA-1 colocalizes with sites of DNA synthesis and the single-stranded DNA binding protein, replication protein A (RPA), in nuclei reconstituted in the egg extract. In addition, we show that two glutathione S-transferase FFA-1 fusion proteins can inhibit DNA replication in a dominant negative manner. The dominant negative effect correlates with the incorporation of the fusion proteins into replication foci to form "hybrid foci," which are unable to engage in DNA replication. At the biochemical level, RPA can interact with FFA-1 and specifically stimulates its DNA helicase activity. However, in the presence of the dominant negative mutant proteins, the stimulation is prevented. These results provide the first direct biochemical evidence of an important role for FFA-1 in DNA replication.

Atypical osteosarcomas in Werner Syndrome (adult progeria)

Werner syndrome (WS), adult progeria, is more common in Japan than elsewhere. It predisposes to osteosarcoma (OS) and five other rare tumors. To determine if and how OS is atypical in this genetic disorder, we studied the characteristics of ten Japanese cases with respect to clinical features, pathology, and radiographs, and compared them with a hospital series of 36 skeletal OS with the same atypical age-range, 35 - 57 years. The anatomic sites were also atypical: seven ankle / foot, two radius and one patella compared with only one at the ankle in the hospital series. The osteoblastic cell-type was about equally frequent in both series, but, among others than the three major subtypes, there was only one in WS as compared with 14 (39%) in the hospital series. The types of mutations were sought in five WS cases with OS. One showed no mutation at any of the ten known loci for Japanese, two were of type 4 / 4 and two of type 6 / 6. The mutations 4 and 6 have been found in 66% of alleles of WS cases in Japan. The increased frequency and unusual age and site distributions of OS in WS may be due to increased susceptibility, related to later-life leg ulcers, and weight-bearing on spindly ankles weakened by severe loss of lower limb subcutaneous tissue.

Werner protein recruits DNA polymerase delta to the nucleolus

Werner syndrome is a Mendelian disorder of man that produces a number of manifestations resembling human aging. This disorder is caused by inactivation of the wrn gene, a member of the RecQ family of DNA helicases. The helicase and exonuclease activities of the Werner protein (WRN) suggest that it functions in DNA transactions, but the physiological function of WRN remains elusive. We present several lines of evidence that WRN interacts specifically with the p50 subunit of polymerase delta, the major DNA polymerase required for chromosomal DNA replication. P50, identified by yeast two-hybrid screening, interacts physically with the C terminus of WRN. Native WRN protein coimmunoprecipitates with p50 in a cellular fraction enriched in nucleolar proteins, and this immunocomplex also includes p125, the catalytic subunit of polymerase delta. In subcellular localization studies of cells transfected with WRN, p50 and p125 redistribute to the nucleolus and colocalize with WRN. These results suggest that one of the functions of WRN protein is to directly modify DNA replication via its interaction with p50 and abet dynamic relocalization of the DNA polymerase delta complexes within the nucleus.

Ku complex interacts with and stimulates the Werner protein

Werner syndrome (WS) is the hallmark premature aging disorder in which affected humans appear older than their chronological age. The protein WRNp, defective in WS, has helicase function, DNA-dependent ATPase, and exonuclease activity. Although WRNp functions in nucleic acid metabolism, there is little or no information about the pathways or protein interactions in which it participates. Here we identify Ku70 and Ku86 as proteins that interact with WRNp. Although Ku proteins had no effect on ATPase or helicase activity, they strongly stimulated specific exonuclease activity. These results suggest that WRNp and the Ku complex participate in a common DNA metabolic pathway.