ABSTRACT
Berardinelli-Seip congenital lipodystrophy type 2 (CGL2) is a very rare human genetic disorder with potential significance to the understanding of the pathobiology of aging. CGL2 patients display characteristic progeroid features and suffer from type 2 diabetes, insulin resistance and fatty liver. In this study, we profiled genome-wide DNA methylation levels in CGL2 patients with BSCL2 mutations to study epigenetic age acceleration and DNA methylation alterations. This analysis revealed significant age acceleration in blood DNA of CGL2 patients using both first- and second-generation epigenetic clocks. We also observed a shortened lifespan of Caenorhabditis elegans following knockdown of the BSCL2 homolog seip-1 on a daf-16/forkhead box, class O mutant background. DNA methylation analysis revealed significant differentially methylated sites enriched for lyase activity, kinase regulator activity, protein kinase regulator activity and kinase activator activity. We could also observe significant hypomethylation in the promoter of the dual specificity phosphatase 22 gene when comparing CGL2 patients versus controls. We conclude that in line with the observed progeroid features, CGL2 patients exhibit significant epigenetic age acceleration and DNA methylation alterations that might affect pathways/genes of potential relevance to the disease.
Subject(s)
Diabetes Mellitus, Type 2 , GTP-Binding Protein gamma Subunits , Lipodystrophy, Congenital Generalized , Lipodystrophy , Humans , Lipodystrophy, Congenital Generalized/genetics , DNA Methylation/genetics , Diabetes Mellitus, Type 2/genetics , Mutation , Aging/genetics , Epigenesis, Genetic , Lipodystrophy/geneticsABSTRACT
BACKGROUND: Werner syndrome (WS) is an autosomal recessive progeroid syndrome caused by variants in WRN. The International Registry of Werner Syndrome has identified biallelic pathogenic variants in 179/188 cases of classical WS. In the remaining nine cases, only one heterozygous pathogenic variant has been identified. METHODS: Targeted long-read sequencing (T-LRS) on an Oxford Nanopore platform was used to search for a second pathogenic variant in WRN. Previously, T-LRS was successfully used to identify missing variants and analyse complex rearrangements. RESULTS: We identified a second pathogenic variant in eight of nine unsolved WS cases. In five cases, T-LRS identified intronic splice variants that were confirmed by either RT-PCR or exon trapping to affect splicing; in one case, T-LRS identified a 339 kbp deletion, and in two cases, pathogenic missense variants. Phasing of long reads predicted all newly identified variants were on a different haplotype than the previously known variant. Finally, in one case, RT-PCR previously identified skipping of exon 20; however, T-LRS did not detect a pathogenic DNA sequence variant. CONCLUSION: T-LRS is an effective method for identifying missing pathogenic variants. Although limitations with computational prediction algorithms can hinder the interpretation of variants, T-LRS is particularly effective in identifying intronic variants.
ABSTRACT
Pathogenic variants in genes, which encode DNA repair and damage response proteins, result in a number of genomic instability syndromes with features of accelerated aging. ERCC4 (XPF) encodes a protein that forms a complex with ERCC1 and is required for the 5' incision during nucleotide excision repair. ERCC4 is also FANCQ, illustrating a critical role in interstrand crosslink repair. Pathogenic variants in this gene cause xeroderma pigmentosum, XFE progeroid syndrome, Cockayne syndrome (CS), and Fanconi anemia. We performed massive parallel sequencing for 42 unsolved cases submitted to the International Registry of Werner Syndrome. Two cases, each carrying two novel heterozygous ERCC4 variants, were identified. The first case was a compound heterozygote for: c.2395C > T (p.Arg799Trp) and c.388+1164_792+795del (p.Gly130Aspfs*18). Further molecular and cellular studies indicated that the ERCC4 variants in this patient are responsible for a phenotype consistent with a variant of CS. The second case was heterozygous for two variants in cis: c.[1488A > T; c.2579C > A] (p.[Gln496His; Ala860Asp]). While the second case also had several phenotypic features of accelerated aging, we were unable to provide biological evidence supporting the pathogenic roles of the associated ERCC4 variants. Precise genetic causes and disease mechanism of the second case remains to be determined.
Subject(s)
Cockayne Syndrome/genetics , DNA-Binding Proteins/genetics , Xeroderma Pigmentosum/genetics , Actins/genetics , Aged , DNA Repair/genetics , DNA-Binding Proteins/chemistry , Fanconi Anemia/genetics , Female , Genetic Predisposition to Disease/genetics , Humans , Lamin Type A/genetics , Male , Middle Aged , PedigreeABSTRACT
Werner syndrome (WS) is a rare autosomal recessive disorder characterized by a constellation of adult onset phenotypes consistent with an acceleration of intrinsic biological aging. It is caused by pathogenic variants in the WRN gene, which encodes a multifunctional nuclear protein with exonuclease and helicase activities. WRN protein is thought to be involved in optimization of various aspects of DNA metabolism, including DNA repair, recombination, replication, and transcription. In this update, we summarize a total of 83 different WRN mutations, including eight previously unpublished mutations identified by the International Registry of Werner Syndrome (Seattle, WA) and the Japanese Werner Consortium (Chiba, Japan), as well as 75 mutations already reported in the literature. The Seattle International Registry recruits patients from all over the world to investigate genetic causes of a wide variety of progeroid syndromes in order to contribute to the knowledge of basic mechanisms of human aging. Given the unusually high prevalence of WS patients and heterozygous carriers in Japan, the major goal of the Japanese Consortium is to develop effective therapies and to establish management guidelines for WS patients in Japan and elsewhere. This review will also discuss potential translational approaches to this disorder, including those currently under investigation.
Subject(s)
Mutation , Werner Syndrome Helicase/genetics , Werner Syndrome/genetics , Age Factors , Animals , Databases, Genetic , Disease Models, Animal , Exons , Gene Frequency , Genetic Association Studies , Genetic Predisposition to Disease , Geography , Humans , Japan , Mice , Phenotype , Polymorphism, Genetic , Polymorphism, Single Nucleotide , Registries , Translational Research, Biomedical , Web Browser , Werner Syndrome/diagnosis , Werner Syndrome/epidemiologyABSTRACT
Congenital generalized lipodystrophy (CGL) is a genetically heterogeneous group of disorders characterized by the absence of functional adipose tissue. We identified two pedigrees with CGL in the community of the Mestizo tribe in the northern region of Peru. Five cases, ranging from 15 months to 7 years of age, presented with generalized lipodystrophy, muscular prominence, mild intellectual disability, and a striking aged appearance. Sequencing of the BSCL2 gene, known to be mutated in type 2 CGL (CGL2; Berardinelli-Seip syndrome), revealed a homozygous deletion of exon 3 in all five patients examined, suggesting the presence of a founder mutation. This intragenic deletion appeared to be mediated by recombination between Alu sequences in introns 2 and 3. CGL2 in this population is likely underdiagnosed and undertreated because of its geographical, socio-economic, and cultural isolation.© 2016 Wiley Periodicals, Inc.
Subject(s)
GTP-Binding Protein gamma Subunits/genetics , Lipodystrophy, Congenital Generalized/diagnosis , Lipodystrophy, Congenital Generalized/genetics , Mutation , Phenotype , Recombination, Genetic , Base Sequence , Child , Child, Preschool , Consanguinity , Exons , Facies , Female , Founder Effect , Genetic Association Studies , Humans , Incidence , Infant , Male , Pedigree , PeruABSTRACT
BACKGROUND: The American Society of Dermatologic Surgery (ASDS) periodically develops consensus documents for its members concerning various aspects of dermatologic surgery. Advances in photodynamic therapy (PDT) have been many and PDT use has been established in a variety of skin conditions. OBJECTIVE: The ASDS board of directors proposed a committee of experts in the field to develop consensus documents on different treatments. An expert panel reviewed the literature on PDT and discussed the findings. The consensus was reached with evidence-based recommendations on different clinical applications for PDT. PATIENTS AND METHODS: This consensus document includes discussions regarding PDT, including different photosensitizers and various light source activators, historical perspective, mechanism of action, various therapeutic indications and expected outcomes, pre- and post-care, and management of adverse outcomes. RESULTS: Photodynamic therapy is highly effective for pre-cancerous lesions, superficial nonmelanoma skin cancers, inflammatory acne vulgaris and other conditions. New protocols including laser mediated PDT significantly improve results for several indications. CONCLUSION: The ASDS consensus document on PDT will be helpful for educating members on safe and effective PDT for a variety of indications.
Subject(s)
Acne Vulgaris/drug therapy , Bowen's Disease/drug therapy , Carcinoma, Basal Cell/drug therapy , Keratosis, Actinic/drug therapy , Photochemotherapy/standards , Skin Neoplasms/drug therapy , Cheilitis/drug therapy , Consensus , Evidence-Based Medicine , Humans , Pain/etiology , Pain Management , Photochemotherapy/adverse effects , Photochemotherapy/instrumentation , Photochemotherapy/methods , Photosensitizing Agents/therapeutic use , Postoperative Care , Preoperative Care , Rejuvenation , Warts/drug therapyABSTRACT
Segmental progeroid syndromes are rare, heterogeneous disorders characterized by signs of premature aging affecting more than one tissue or organ. A prototypic example is the Werner syndrome (WS), caused by biallelic germline mutations in the Werner helicase gene (WRN). While heterozygous lamin A/C (LMNA) mutations are found in a few nonclassical cases of WS, another 10%-15% of patients initially diagnosed with WS do not have mutations in WRN or LMNA. Germline POLD1 mutations were recently reported in five patients with another segmental progeroid disorder: mandibular hypoplasia, deafness, progeroid features syndrome. Here, we describe eight additional patients with heterozygous POLD1 mutations, thereby substantially expanding the characterization of this new example of segmental progeroid disorders. First, we identified POLD1 mutations in patients initially diagnosed with WS. Second, we describe POLD1 mutation carriers without clinically relevant hearing impairment or mandibular underdevelopment, both previously thought to represent obligate diagnostic features. These patients also exhibit a lower incidence of metabolic abnormalities and joint contractures. Third, we document postnatal short stature and premature greying/loss of hair in POLD1 mutation carriers. We conclude that POLD1 germline mutations can result in a variably expressed and probably underdiagnosed segmental progeroid syndrome.
Subject(s)
Cockayne Syndrome/diagnosis , Cockayne Syndrome/genetics , DNA Polymerase III/genetics , Germ-Line Mutation , Werner Syndrome/diagnosis , Adolescent , Adult , Alleles , Amino Acid Substitution , Cell Line, Transformed , Child , Chromosomal Instability , Chromosome Aberrations , DNA Mutational Analysis , DNA Polymerase III/chemistry , Diagnosis, Differential , Facies , Female , Genotype , Humans , Male , Middle Aged , Models, Molecular , Phenotype , Protein Conformation , Registries , Young AdultABSTRACT
We describe a 28-year-old Turkish man with consanguineous parents who presented with an aged appearance with prematurely gray hair and scleroderma-like skin, spastic paraplegia, and apparent disability. The proband and each of his parents were heterozygous for a mutation in WRN, which could not explain his symptoms. Exome sequencing of the proband's blood DNA showed a homozygous c.626-1G > C mutation in intron 5 of the SAMHD1 gene, which encodes a triphosphohydrolase involved in the regulation of intracellular dNTP pools and which is mutated in Aicardi-Goutieres syndrome. The RNA studies confirmed aberrant splicing of exon 6, and family studies showed that both parents are heterozygous for this mutation. We conclude that mutations in SAMHD1 - in addition to causing an early-onset form of encephalopathy in Aicardi-Goutieres syndrome - may present with modest signs of accelerated aging similar to Werner syndrome. The extent to which heterozygosity at the WRN locus may modify the effect of biallelic SAMHD1 mutations is unknown. It is conceivable that synergistic effects of these two mutations might be responsible for the unusual phenotype.
Subject(s)
Autoimmune Diseases of the Nervous System/genetics , Exodeoxyribonucleases/genetics , Nervous System Malformations/genetics , RecQ Helicases/genetics , Adult , Heterozygote , Homozygote , Humans , Male , Monomeric GTP-Binding Proteins/genetics , Mutation/genetics , SAM Domain and HD Domain-Containing Protein 1 , Werner Syndrome/genetics , Werner Syndrome HelicaseABSTRACT
INTRODUCTION: Brodalumab is a human interleukin-17 receptor A antagonist indicated for the treatment of moderate-to-severe plaque psoriasis in adult patients who are candidates for systemic therapy or phototherapy and have failed to respond or have lost response to other systemic therapies. Although the US prescribing information for brodalumab includes a boxed warning regarding suicidal ideation and behavior, no causal association has been demonstrated. Here, we summarize 5 years of pharmacovigilance data, from August 15, 2017, through August 14, 2022, reported to Ortho Dermatologics by US patients and healthcare providers. METHODS: Prevalence of the most common adverse events (AEs) listed in the brodalumab package insert (incidence ≥ 1%) and AEs of special interest are described. Brodalumab exposure was estimated as the time from the first to last prescription-dispensing authorization dates. Data were collected from 4744 patients in the USA, with an estimated exposure of 5815 patient-years. RESULTS: Over 5 years, 11 cases of adjudicated major adverse cardiovascular events were reported (0.23 events/100 patients), a rate lower than that experienced by patients in the international Psoriasis Longitudinal Assessment and Registry. There were 106 serious infections. No serious fungal infections were reported. There were 40 confirmed and 2 suspected COVID-19 cases, with no new COVID-19-related deaths. Of 49 reported malignancies among 42 patients, 3 were deemed possibly related to brodalumab. No completed suicides and no new suicidal attempts were reported. CONCLUSION: Five-year pharmacovigilance data are consistent with the established safety profile reported in long-term clinical trials and previous pharmacovigilance reports, with no new safety signals.
Brodalumab is an injectable treatment approved for moderate-to-severe plaque psoriasis in adults who lacked response to previous treatments. In the USA, brodalumab is only available under a Risk Evaluation and Mitigation Strategy for increased suicidality risks; however, findings from 5 years of real-world safety data have demonstrated a lack of association. In this report, we discuss safety findings reported by US patients and healthcare providers for 4744 patients treated with brodalumab over 5 years. Joint pain (known as arthralgia) was the most common safety finding, with 122 cases reported over 5 years. Other safety findings of interest across 5 years included 106 serious infections (defined as prolonged infections or infections requiring treatment), 54 cases of depression, 49 cases of cancer (in 42 patients), 40 confirmed cases of COVID-19, and 11 cases of major cardiovascular events (such as stroke or heart attack). No completed suicides occurred throughout 5 years, and no new suicidal attempts were reported in year 5. In indirect comparisons with safety data from patients with psoriasis receiving or eligible to receive similar treatments, brodalumab was not associated with an increased risk of serious infection, cancer, major cardiovascular events, or inflammatory bowel disease. Taken together, these data are consistent with safety findings from long-term clinical trials and previous safety reports of brodalumab.
ABSTRACT
In this contribution to the series of reflective essays celebrating the 25th anniversary of The FASEB Journal, our task is to assess the growth of research on the biology of aging during this period and to suggest where we might be heading during the next 25 yr. A review of the literature suggests a healthy acceleration of progress during the past decade, perhaps largely due to progress on the genetics of longevity of model organisms. Progress on the genetics of health span in these model organisms has lagged, however. Research on the genetic basis of the remarkable interspecific variations in life span has only recently begun to be seriously addressed. The spectacular advances in genomics should greatly accelerate progress. Research on environmental effects on life span and health span needs to be accelerated. Stochastic variations in gene expression in aging have only recently been addressed. These can lead to random departures from homeostasis during aging.-Martin, G. M. The biology of aging: 1985-2010 and beyond.
Subject(s)
Aging/physiology , Aging/genetics , Animals , Caenorhabditis elegans , Caloric Restriction , Drosophila melanogaster , Epigenesis, Genetic/physiology , Free Radicals/metabolism , Gene Expression , Humans , Life Expectancy , Longevity/genetics , Mice , Mitochondria/metabolism , Regenerative Medicine , Resveratrol , Stem Cells/physiology , Stilbenes/pharmacology , Telomerase/geneticsABSTRACT
BACKGROUND: Diclofenac sodium 3% gel (Solaraze®) gained US approval for the treatment of actinic keratosis (AK) more than 10 years ago. Since the publication of the pivotal phase 3 studies, numerous clinical studies have assessed use of this therapy in a variety of body areas, special populations, and novel combinations. OBJECTIVE: To provide a comprehensive update on clinical data and research on the use of diclofenac sodium 3% gel in AK. METHODS: Review of the literature. RESULTS: Accumulating evidence from preclinical research supports that the proposed mechanism of diclofenac sodium 3% gel may include cyclo-oxgenase 2 (COX-2) inhibition, inhibition of angiogenesis, and induction of apoptosis. A literature review identified 17 publications (beyond the 2 pivotal studies) on the use of diclofenac sodium 3% gel for AK. A phase 4 open-label study reported that 58 percent of patients achieved complete clearance of target lesions at the 30-day post-treatment assessment; among patients who were evaluable at 1-year post-treatment, sustained long-term clearance of AK lesions was observed. Active comparator studies demonstrated comparable efficacy of diclofenac sodium 3% gel with 5-fluorouracil 5% and imiquimod 5%. Publications on the efficacy of diclofenac sodium 3% gel for AK of the lip report complete clearance rates comparable to those reported for other body areas. Diclofenac sodium 3% gel has also demonstrated efficacy for clearing AK lesions in immunosuppressed populations. Sequential use of diclofenac sodium 3% gel with cryosurgery or photodynamic therapy has been investigated and may emerge as a useful approach for some patients. CONCLUSIONS: Diclofenac sodium 3% gel has a unique proposed mechanism of action in AK that may involve COX-2 inhibition, inhibition of angiogenesis, and induction of apoptosis. In the past decade, numerous clinical studies have demonstrated this topical therapy to be effective and well tolerated for the treatment of AK.
Subject(s)
Anti-Inflammatory Agents, Non-Steroidal/therapeutic use , Diclofenac/therapeutic use , Keratosis, Actinic/drug therapy , Administration, Cutaneous , Angiogenesis Inhibitors/administration & dosage , Angiogenesis Inhibitors/adverse effects , Angiogenesis Inhibitors/therapeutic use , Anti-Inflammatory Agents, Non-Steroidal/administration & dosage , Anti-Inflammatory Agents, Non-Steroidal/adverse effects , Apoptosis/drug effects , Clinical Trials as Topic , Cyclooxygenase 2 Inhibitors/administration & dosage , Cyclooxygenase 2 Inhibitors/adverse effects , Cyclooxygenase 2 Inhibitors/therapeutic use , Diclofenac/administration & dosage , Diclofenac/adverse effects , Gels , Humans , Keratosis, Actinic/pathologyABSTRACT
Older age and underlying conditions such as diabetes/obesity or immunosuppression are leading host risk factors for developing severe complications from COVID-19 infection. The pathogenesis of COVID-19-related cytokine storm, tissue damage, and fibrosis may be interconnected with fundamental aging processes, including dysregulated immune responses and cellular senescence. Here, we examined effects of key cytokines linked to cellular senescence on expression of SARS-CoV-2 viral entry receptors. We found exposure of human umbilical vein endothelial cells (HUVECs) to the inflammatory cytokines, TNF-α + IFN-γ or a cocktail of TNF-α + IFN-γ + IL-6, increased expression of ACE2/DPP4, accentuated the pro-inflammatory senescence-associated secretory phenotype (SASP), and decreased cellular proliferative capacity, consistent with progression towards a cellular senescence-like state. IL-6 by itself failed to induce substantial effects on viral entry receptors or SASP-related genes, while synergy between TNF-α and IFN-γ initiated a positive feedback loop via hyper-activation of the JAK/STAT1 pathway, causing SASP amplification. Breaking the interactive loop between senescence and cytokine secretion with JAK inhibitor ruxolitinib or antiviral drug remdesivir prevented hyper-inflammation, normalized SARS-CoV-2 entry receptor expression, and restored HUVECs proliferative capacity. This loop appears to underlie cytokine-mediated viral entry receptor activation and links with senescence and hyper-inflammation.
Subject(s)
COVID-19 Drug Treatment , COVID-19 , Interferon-gamma , SARS-CoV-2 , Tumor Necrosis Factor-alpha , COVID-19/virology , Cytokines/immunology , Drug Synergism , Human Umbilical Vein Endothelial Cells/metabolism , Humans , Inflammation/drug therapy , Inflammation/virology , Interferon-gamma/pharmacology , Interleukin-6/metabolism , Receptors, Virus/metabolism , SARS-CoV-2/drug effects , SARS-CoV-2/metabolism , STAT1 Transcription Factor/biosynthesis , STAT1 Transcription Factor/immunology , Tumor Necrosis Factor-alpha/pharmacologyABSTRACT
Hutchinson-Gilford Progeria Syndrome (HGPS) is an extremely rare genetic disorder caused by mutations in the LMNA gene and characterized by premature and accelerated aging beginning in childhood. In this study, we performed the first genome-wide methylation analysis on blood DNA of 15 patients with progeroid laminopathies using Infinium Methylation EPIC arrays including 8 patients with classical HGPS. We could observe DNA methylation alterations at 61 CpG sites as well as 32 significant regions following a 5 Kb tiling analysis. Differentially methylated probes were enriched for phosphatidylinositol biosynthetic process, phospholipid biosynthetic process, sarcoplasm, sarcoplasmic reticulum, phosphatase regulator activity, glycerolipid biosynthetic process, glycerophospholipid biosynthetic process, and phosphatidylinositol metabolic process. Differential methylation analysis at the level of promoters and CpG islands revealed no significant methylation changes in blood DNA of progeroid laminopathy patients. Nevertheless, we could observe significant methylation differences in classic HGPS when specifically looking at probes overlapping solo-WCGW partially methylated domains. Comparing aberrantly methylated sites in progeroid laminopathies, classic Werner syndrome, and Down syndrome revealed a common significantly hypermethylated region in close vicinity to the transcription start site of a long non-coding RNA located anti-sense to the Catenin Beta Interacting Protein 1 gene (CTNNBIP1). By characterizing epigenetically altered sites, we identify possible pathways/mechanisms that might have a role in the accelerated aging of progeroid laminopathies.
Subject(s)
Progeria , Werner Syndrome , Aging/genetics , DNA/genetics , DNA/metabolism , DNA Methylation/genetics , Humans , Lamin Type A/genetics , Lamin Type A/metabolism , Mutation , Progeria/genetics , Progeria/metabolism , Werner Syndrome/geneticsABSTRACT
Classical Hutchinson-Gilford progeria syndrome (HGPS) is caused by LMNA mutations that generate an alternatively spliced form of lamin A, termed progerin. HGPS patients present in early childhood with atherosclerosis and striking features of accelerated aging. We report on two pedigrees of adult-onset coronary artery disease with progeroid features, who were referred to our International Registry of Werner Syndrome (WS) because of clinical features consistent with the diagnosis. No mutations were identified in the WRN gene that is responsible for WS, among these patients. Instead, we found two novel heterozygous mutations at the junction of exon 10 and intron 11 of the LMNA gene. These mutations resulted in the production of progerin at a level substantially lower than that of HGPS. Our findings indicate that LMNA mutations may result in coronary artery disease presenting in the fourth to sixth decades along with short stature and a progeroid appearance resembling WS. The absence of early-onset cataracts in this setting should suggest the diagnosis of progeroid laminopathy. This study illustrates the evolving genotype-phenotype relationship between the amount of progerin produced and the age of onset among the spectrum of restrictive dermopathy, HGPS, and atypical forms of WS.
Subject(s)
Alternative Splicing , Coronary Artery Disease/etiology , Coronary Artery Disease/genetics , Lamin Type A/genetics , Nuclear Proteins/genetics , Progeria/complications , Progeria/genetics , Protein Precursors/genetics , Adolescent , Adult , Base Sequence , Child , Coronary Artery Disease/diagnosis , Exons , Facies , Female , Humans , Male , Middle Aged , Mutation , Progeria/diagnosis , Werner Syndrome/genetics , Young AdultABSTRACT
The purpose of this early contribution to the new Fellows Forum of this pioneering journal for what is now called Geroscience is to provide an example of how the author's interest in using the emerging tools of human genetics has led to strong support for one of the hallmarks of aging-Genomic Instability. We shall also briefly review our emerging interests in the genetic analysis of what we have called Antigeroid Syndromes. While there has been significant progress in that direction via genetic studies of centenarians, the search for genetic pathways that make individuals unusually resistant or resilient to the ravages of specific geriatric disorders has been comparatively neglected. We refer to these disorders as Unimodal Antigeroid Syndromes. It is our hope that our young colleagues will consider research efforts in that direction.
Subject(s)
Aging/genetics , Genomic Instability , Werner Syndrome/genetics , Alzheimer Disease/genetics , Cockayne Syndrome/genetics , Cockayne Syndrome/pathology , Coronary Artery Disease/genetics , Diabetes Mellitus/genetics , Female , Genetic Research , Humans , Male , Mutation , Phenotype , Progeria/genetics , Progeria/pathology , Syndrome , Werner Syndrome/pathologyABSTRACT
There is tremendous variation in biological traits, and much of it is not accounted for by variation in DNA sequence, including human diseases and lifespan. Emerging evidence points to differences in the execution of the genetic program as a key source of variation, be it stochastic variation or programmed variation. Here we discuss variation in gene expression as an intrinsic property and how it could contribute to variation in traits, including the rate of aging. The review is divided into sections describing the historical context and evidence to date for nongenetic variation, the different approaches that may be used to detect nongenetic variation, and recent findings showing that the amount of variation in gene expression can be both genetically programmed and epigenetically controlled. Finally, we present evidence that changes in cell-to-cell variation in gene expression emerge as part of the aging process and may be linked to disease vulnerability as a function of age. These emerging concepts are likely to be important across the spectrum of biomedical research and may well underpin what we understand as biological aging.
Subject(s)
Aging , Longevity , Aging/genetics , Gene Expression , Humans , Longevity/genetics , PhenotypeABSTRACT
SMAD4 encodes a member of the SMAD family of proteins involved in the TGF-ß signaling pathway. Potentially heritable, autosomal dominant, gain-of-function heterozygous variants of SMAD4 cause a rare developmental disorder, the Myhre syndrome, which is associated with a wide range of developmental and post-developmental phenotypes that we now characterize as a novel segmental progeroid syndrome. Whole-exome sequencing of a patient referred to our International Registry of Werner Syndrome revealed a heterozygous p.Arg496Cys variant of the SMAD4 gene. To investigate the role of SMAD4 mutations in accelerated senescence, we generated cellular models overexpressing either wild-type SMAD4 or mutant SMAD4-R496C in normal skin fibroblasts. We found that cells expressing the SMAD4-R496C mutant exhibited decreased proliferation and elevated expression of cellular senescence and inflammatory markers, including IL-6, IFNγ, and a TGF-ß target gene, PAI-1. Here we show that transient exposure to TGF-ß, an inflammatory cytokine, followed by chronic IFNγ stimulation, accelerated rates of senescence that were associated with increased DNA damage foci and SMAD4 expression. TGF-ß, IFNγ, or combinations of both were not sufficient to reduce proliferation rates of fibroblasts. In contrast, TGF-ß alone was able to induce preadipocyte senescence via induction of the mTOR protein. The mTOR inhibitor rapamycin mitigated TGF-ß-induced expression of p21, p16, and DNA damage foci and improved replicative potential of preadipocytes, supporting the cell-specific response to this cytokine. These findings collectively suggest that persistent DNA damage and cross-talk between TGF-ß/IFNγ pathways contribute to a series of molecular events leading to cellular senescence and a segmental progeroid syndrome.
Subject(s)
Cellular Senescence , DNA Damage , Cellular Senescence/genetics , Cryptorchidism , DNA Damage/genetics , Facies , Growth Disorders , Hand Deformities, Congenital , Humans , Intellectual Disability , Mutation , Smad4 Protein/genetics , Transforming Growth Factor beta/geneticsSubject(s)
Diphosphonates/therapeutic use , Imidazoles/therapeutic use , Nuclear Proteins/metabolism , Piperidines/therapeutic use , Pravastatin/therapeutic use , Progeria/drug therapy , Protein Precursors/metabolism , Protein Prenylation/drug effects , Pyridines/therapeutic use , Female , Humans , Lamin Type A , Male , Zoledronic AcidABSTRACT
BACKGROUND: Age is a major risk for cardiovascular diseases. Although mitochondrial reactive oxygen species have been proposed as one of the causes of aging, their role in cardiac aging remains unclear. We have previously shown that overexpression of catalase targeted to mitochondria (mCAT) prolongs murine median lifespan by 17% to 21%. METHODS AND RESULTS: We used echocardiography to study cardiac function in aging cohorts of wild-type and mCAT mice. Changes found in wild-type mice recapitulate human aging: age-dependent increases in left ventricular mass index and left atrial dimension, worsening of the myocardial performance index, and a decline in diastolic function. Cardiac aging in mice is accompanied by accumulation of mitochondrial protein oxidation, increased mitochondrial DNA mutations and deletions and mitochondrial biogenesis, increased ventricular fibrosis, enlarged myocardial fiber size, decreased cardiac SERCA2 protein, and activation of the calcineurin-nuclear factor of activated T-cell pathway. All of these age-related changes were significantly attenuated in mCAT mice. Analysis of survival of 130 mice demonstrated that echocardiographic cardiac aging risk scores were significant predictors of mortality. The estimated attributable risk to mortality for these 2 parameters was 55%. CONCLUSIONS: This study shows that cardiac aging in the mouse closely recapitulates human aging and demonstrates the critical role of mitochondrial reactive oxygen species in cardiac aging and the impact of cardiac aging on survival. These findings also support the potential application of mitochondrial antioxidants in reactive oxygen species-related cardiovascular diseases.