Gene expression profiling in Werner syndrome closely resembles that of normal aging

RecQ Helicase Somatic Alterations in Cancer

Named the “caretakers” of the genome, RecQ helicases function in several pathways to maintain genomic stability and repair DNA. This highly conserved family of enzymes consist of five different proteins in humans: RECQL1, BLM, WRN, RECQL4, and RECQL5. Biallelic germline mutations in BLM, WRN, and RECQL4 have been linked to rare cancer-predisposing syndromes. Emerging research has also implicated somatic alterations in RecQ helicases in a variety of cancers, including hematological malignancies, breast cancer, osteosarcoma, amongst others. These alterations in RecQ helicases, particularly overexpression, may lead to increased resistance of cancer cells to conventional chemotherapy. Downregulation of these proteins may allow for increased sensitivity to chemotherapy, and, therefore, may be important therapeutic targets. Here we provide a comprehensive review of our current understanding of the role of RecQ DNA helicases in cancer and discuss the potential therapeutic opportunities in targeting these helicases.

Chemically induced senescence in human stem cell-derived neurons promotes phenotypic presentation of neurodegeneration

Modeling age‐related neurodegenerative disorders with human stem cells are difficult due to the embryonic nature of stem cell‐derived neurons. We developed a chemical cocktail to induce senescence of iPSC‐derived neurons to address this challenge. We first screened small molecules that induce embryonic fibroblasts to exhibit features characteristic of aged fibroblasts. We then optimized a cocktail of small molecules that induced senescence in fibroblasts and cortical neurons without causing DNA damage. The utility of the “senescence cocktail” was validated in motor neurons derived from ALS patient iPSCs which exhibited protein aggregation and axonal degeneration substantially earlier than those without cocktail treatment. Our “senescence cocktail” will likely enhance the manifestation of disease‐related phenotypes in neurons derived from iPSCs, enabling the generation of reliable drug discovery platforms.

POLR2A Promotes the Proliferation of Gastric Cancer Cells by Advancing the Overall Cell Cycle Progression

RNA polymerase II subunit A (POLR2A) is the largest subunit encoding RNA polymerase II and closely related to cancer progression. However, the biological role and underlying molecular mechanism of POLR2A in gastric cancer (GC) are still unclear. Our study demonstrated that POLR2A was highly expressed in GC tissue and promoted the proliferation of GC in vitro and in vivo. We also found that POLR2A participated in the transcriptional regulation of cyclins and cyclin-dependent kinases (CDKs) at each stage and promoted their expression, indicated POLR2A’s overall promotion of cell cycle progression. Moreover, POLR2A inhibited GC cell apoptosis and promoted GC cell migration. Our results indicate that POLR2A play an oncogene role in GC, which may be an important factor involved in the occurrence and development of GC.

The Vital Role of Central Executive Network in Brain Age: Evidence From Machine Learning and Transcriptional Signatures

Recent studies combining neuroimaging with machine learning methods successfully infer an individual’s brain age, and its discrepancy with the chronological age is used to identify age-related diseases. However, which brain networks play decisive roles in brain age prediction and the underlying biological basis of brain age remain unknown. To answer these questions, we estimated an individual’s brain age in the Southwest University Adult Lifespan Dataset (N = 492) from the gray matter volumes (GMV) derived from T1-weighted MRI scans by means of Gaussian process regression. Computational lesion analysis was performed to determine the importance of each brain network in brain age prediction. Then, we identified brain age-related genes by using prior brain-wide gene expression data, followed by gene enrichment analysis using Metascape. As a result, the prediction model successfully inferred an individual’s brain age and the computational lesion prediction results identified the central executive network as a vital network in brain age prediction (Steiger’s Z = 2.114, p = 0.035). In addition, the brain age-related genes were enriched in Gene Ontology (GO) processes/Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways grouped into numbers of clusters, such as regulation of iron transmembrane transport, synaptic signaling, synapse organization, retrograde endocannabinoid signaling (e.g., dopaminergic synapse), behavior (e.g., memory and associative learning), neurotransmitter secretion, and dendrite development. In all, these results reveal that the GMV of the central executive network played a vital role in predicting brain age and bridged the gap between transcriptome and neuroimaging promoting an integrative understanding of the pathophysiology of brain age.

Human WRN is an intrinsic inhibitor of progerin, abnormal splicing product of lamin A

Werner syndrome (WRN) is a rare progressive genetic disorder, caused by functional defects in WRN protein and RecQ4L DNA helicase. Acceleration of the aging process is initiated at puberty and the expected life span is approximately the late 50 s. However, a Wrn-deficient mouse model does not show premature aging phenotypes or a short life span, implying that aging processes differ greatly between humans and mice. Gene expression analysis of WRN cells reveals very similar results to gene expression analysis of Hutchinson Gilford progeria syndrome (HGPS) cells, suggesting that these human progeroid syndromes share a common pathological mechanism. Here we show that WRN cells also express progerin, an abnormal variant of the lamin A protein. In addition, we reveal that duplicated sequences of human WRN (hWRN) from exon 9 to exon 10, which differ from the sequence of mouse WRN (mWRN), are a natural inhibitor of progerin. Overexpression of hWRN reduced progerin expression and aging features in HGPS cells. Furthermore, the elimination of progerin by siRNA or a progerin-inhibitor (SLC-D011 also called progerinin) can ameliorate senescence phenotypes in WRN fibroblasts and cardiomyocytes, derived from WRN-iPSCs. These results suggest that progerin, which easily accumulates under WRN-deficient conditions, can lead to premature aging in WRN and that this effect can be prevented by SLC-D011.

XAB2 depletion induces intron retention in POLR2A to impair global transcription and promote cellular senescence

XAB2 is a multi-functional protein participating processes including transcription, splicing, DNA repair and mRNA export. Here, we report POLR2A, the largest catalytic subunit of RNA polymerase II, as a major target gene down-regulated after XAB2 depletion. XAB2 depletion led to severe splicing defects of POLR2A with significant intron retention. Such defects resulted in substantial loss of POLR2A at RNA and protein levels, which further impaired global transcription. Treatment of splicing inhibitor madrasin induced similar reduction of POLR2A. Screen using TMT-based quantitative proteomics identified several proteins involved in mRNA surveillance including Dom34 with elevated expression. Inhibition of translation or depletion of Dom34 rescued the expression of POLR2A by stabilizing its mRNA. Immuno-precipitation further confirmed that XAB2 associated with spliceosome components important to POLR2A expression. Domain mapping revealed that TPR motifs 2–4 and 11 of XAB2 were critical for POLR2A expression by interacting with SNW1. Finally, we showed POLR2A mediated cell senescence caused by XAB2 deficiency. Depletion of XAB2 or POLR2A induced cell senescence by up-regulation of p53 and p21, re-expression of POLR2A after XAB2 depletion alleviated cellular senescence. These data together support that XAB2 serves as a guardian of POLR2A expression to ensure global gene expression and antagonize cell senescence.

Candesartan Neuroprotection in Rat Primary Neurons Negatively Correlates with Aging and Senescence: a Transcriptomic Analysis

Preclinical experiments and clinical trials demonstrated that angiotensin II AT₁ receptor overactivity associates with aging and cellular senescence and that AT₁ receptor blockers (ARBs) protect from age-related brain disorders. In a primary neuronal culture submitted to glutamate excitotoxicity, gene set enrichment analysis (GSEA) revealed expression of several hundred genes altered by glutamate and normalized by candesartan correlated with changes in expression in Alzheimer's patient's hippocampus. To further establish whether our data correlated with gene expression alterations associated with aging and senescence, we compared our global transcriptional data with additional published datasets, including alterations in gene expression in the neocortex and cerebellum of old mice, human frontal cortex after age of 40, gene alterations in the Werner syndrome, rodent caloric restriction, Ras and oncogene-induced senescence in fibroblasts, and to tissues besides the brain such as the muscle and kidney. The most significant and enriched pathways associated with aging and senescence were positively correlated with alterations in gene expression in glutamate-injured neurons and, conversely, negatively correlated when the injured neurons were treated with candesartan. Our results involve multiple genes and pathways, including CAV1, CCND1, CDKN1A, CHEK1, ICAM1, IL-1B, IL-6, MAPK14, PTGS2, SERPINE1, and TP53, encoding proteins associated with aging and senescence hallmarks, such as inflammation, oxidative stress, cell cycle and mitochondrial function alterations, insulin resistance, genomic instability including telomere shortening and DNA damage, and the senescent-associated secretory phenotype. Our results demonstrate that AT₁ receptor blockade ameliorates central mechanisms of aging and senescence. Using ARBs for prevention and treatment of age-related disorders has important translational value.

NAD+ augmentation restores mitophagy and limits accelerated aging in Werner syndrome

Metabolic dysfunction is a primary feature of Werner syndrome (WS), a human premature aging disease caused by mutations in the gene encoding the Werner (WRN) DNA helicase. WS patients exhibit severe metabolic phenotypes, but the underlying mechanisms are not understood, and whether the metabolic deficit can be targeted for therapeutic intervention has not been determined. Here we report impaired mitophagy and depletion of NAD+, a fundamental ubiquitous molecule, in WS patient samples and WS invertebrate models. WRN regulates transcription of a key NAD+ biosynthetic enzyme nicotinamide nucleotide adenylyltransferase 1 (NMNAT1). NAD+ repletion restores NAD+ metabolic profiles and improves mitochondrial quality through DCT-1 and ULK-1-dependent mitophagy. At the organismal level, NAD+ repletion remarkably extends lifespan and delays accelerated aging, including stem cell dysfunction, in Caenorhabditis elegans and Drosophila melanogaster models of WS. Our findings suggest that accelerated aging in WS is mediated by impaired mitochondrial function and mitophagy, and that bolstering cellular NAD+ levels counteracts WS phenotypes.

Epigenetic signatures of Werner syndrome occur early in life and are distinct from normal epigenetic aging processes

Werner Syndrome (WS) is an adult-onset segmental progeroid syndrome. Bisulfite pyrosequencing of repetitive DNA families revealed comparable blood DNA methylation levels between classical (18 WRN-mutant) or atypical WS (3 LMNA-mutant and 3 POLD1-mutant) patients and age- and sex-matched controls. WS was not associated with either age-related accelerated global losses of ALU, LINE1, and α-satellite DNA methylations or gains of rDNA methylation. Single CpG methylation was analyzed with Infinium MethylationEPIC arrays. In a correspondence analysis, atypical WS samples clustered together with the controls and were clearly separated from classical WS, consistent with distinct epigenetic pathologies. In classical WS, we identified 659 differentially methylated regions (DMRs) comprising 3,656 CpG sites and 613 RefSeq genes. The top DMR was located in the HOXA4 promoter. Additional DMR genes included LMNA, POLD1, and 132 genes which have been reported to be differentially expressed in WRN-mutant/depleted cells. DMRs were enriched in genes with molecular functions linked to transcription factor activity and sequence-specific DNA binding to promoters transcribed by RNA polymerase II. We propose that transcriptional misregulation of downstream genes by the absence of WRN protein contributes to the variable premature aging phenotypes of WS. There were no CpG sites showing significant differences in DNA methylation changes with age between WS patients and controls. Genes with both WS- and age-related methylation changes exhibited a constant offset of methylation between WRN-mutant patients and controls across the entire analyzed age range. WS-specific epigenetic signatures occur early in life and do not simply reflect an acceleration of normal epigenetic aging processes.

Acidic domain of WRNp is critical for autophagy and up-regulates age associated proteins

Impaired autophagy may be associated with normal and pathological aging. Here we explore a link between autophagy and domain function of Werner protein (WRNp). Werner (WRN) mutant cell lines AG11395, AG05229 and normal aged fibroblast AG13129 display a deficient response to tunicamycin mediated endoplasmic reticulum (ER) stress induced autophagy compared to clinically unaffected GM00637 and normal young fibroblast GM03440. Cellular endoplasmic reticulum (ER) stress mediated autophagy in WS and normal aged cells is restored after transfection with wild type full length WRN, but deletion of the acidic domain from wild type WRN fails to restore autophagy. The acidic domain of WRNp was shown to regulate its transcriptional activity, and here, we show that it affects the transcription of certain proteins involved in autophagy and aging. Furthermore, siRNA mediated silencing of WRN in normal fibroblast WI-38 resulted in decrease of age related proteins Lamin A/C and Mre11.

Residues in the RecQ C-terminal Domain of the Human Werner Syndrome Helicase Are Involved in Unwinding G-quadruplex DNA

The structural and biophysical properties typically associated with G-quadruplex (G4) structures render them a significant block for DNA replication, which must be overcome for cell division to occur. The Werner syndrome protein (WRN) is a RecQ family helicase that has been implicated in the efficient processing of G4 DNA structures. The aim of this study was to identify the residues of WRN involved in the binding and ATPase-driven unwinding of G4 DNA. Using a c-Myc G4 DNA model sequence and recombinant WRN, we have determined that the RecQ-C-terminal (RQC) domain of WRN imparts a 2-fold preference for binding to G4 DNA relative to non-G4 DNA substrates. NMR studies identified residues involved specifically in interactions with G4 DNA. Three of the amino acids in the WRN RQC domain that exhibited the largest G4-specific changes in NMR signal were then mutated alone or in combination. Mutating individual residues implicated in G4 binding had a modest effect on WRN binding to DNA, decreasing the preference for G4 substrates by ∼25%. Mutating two G4-interacting residues (T1024G and T1086G) abrogated preferential binding of WRN to G4 DNA. Very modest decreases in G4 DNA-stimulated ATPase activity were observed for the mutant enzymes. Most strikingly, G4 unwinding by WRN was inhibited ∼50% for all three point mutants and >90% for the WRN double mutant (T1024G/T1086G) relative to normal B-form dsDNA substrates. Our work has helped to identify residues in the WRN RQC domain that are involved specifically in the interaction with G4 DNA.

Genetic variation in WRN and ischemic stroke: General population studies and meta-analyses

BACKGROUND

Werner syndrome, a premature genetic aging syndrome, shares many clinical features reminiscent of normal physiological aging, and ischemic vascular disease is a frequent cause of death. We tested the hypothesis that genetic variation in the WRN gene was associated with risk of ischemic vascular disease in the general population.

METHODS

We included 58,284 participants from two general population cohorts, the Copenhagen City Heart Study (CCHS) and the Copenhagen General Population Study (CGPS). Of these, 6,312 developed ischemic vascular disease during follow-up. In the CCHS (n=10,250), we genotyped all non-synonymous variants in WRN with reported minor allele frequencies ≥0.5% in Caucasians. Second, variants which were associated with ischemic vascular disease in the CCHS or in previous studies, were genotyped in the CGPS (n=48,034).

RESULTS

A total of 11 non-synonymous variants were identified in the CCHS. In C1367R (rs1346044) TT homozygotes versus CC/CT, hazard ratios for ischemic stroke were 1.09 (95% confidence interval: 0.95-1.24; P=0.22) in the CCHS, 1.16 (1.00-1.33; P=0.04) in the CGPS, and 1.12 (1.01-1.23; P=0.02) in studies combined (CCHS+CGPS), with similar trends for ischemic cerebrovascular disease (P=0.06). In meta-analyses including 59,190 individuals in 5 studies, the hazard ratio for ischemic stroke for C1367R TT homozygotes versus CC/CT was 1.14 (1.04-1.25; P=0.008).

CONCLUSIONS

This study suggests that common genetic variation in WRN is associated with increased risk of ischemic stroke in the general population.

The Expression Levels of XLF and Mutant P53 Are Inversely Correlated in Head and Neck Cancer Cells

XRCC4-like factor (XLF), also known as Cernunnos, is a protein encoded by the human NHEJ1 gene and an important repair factor for DNA double-strand breaks. In this study, we have found that XLF is over-expressed in HPV(+) versus HPV(-) head and neck squamous cell carcinoma (HNSCC) and significantly down-regulated in the HNSCC cell lines expressing high level of mutant p53 protein versus those cell lines harboring wild-type TP53 gene with low p53 protein expression. We have also demonstrated that Werner syndrome protein (WRN), a member of the NHEJ repair pathway, binds to both mutant p53 protein and NHEJ1 gene promoter, and siRNA knockdown of WRN leads to the inhibition of XLF expression in the HNSCC cells. Collectively, these findings suggest that WRN and p53 are involved in the regulation of XLF expression and the activity of WRN might be affected by mutant p53 protein in the HNSCC cells with aberrant TP53 gene mutations, due to the interaction of mutant p53 with WRN. As a result, the expression of XLF in these cancer cells is significantly suppressed. Our study also suggests that XLF is over-expressed in HPV(+) HNSCC with low expression of wild type p53, and might serve as a potential biomarker for HPV(+) HNSCC. Further studies are warranted to investigate the mechanisms underlying the interactive role of WRN and XLF in NHEJ repair pathway.

The Werner syndrome RECQ helicase targets G4 DNA in human cells to modulate transcription

The Werner syndrome (WS) is a prototypic adult Mendelian progeroid syndrome in which signs of premature aging are associated with genomic instability and an elevated risk of cancer. The WRN RECQ helicase protein binds and unwinds G-quadruplex (G4) DNA substrates in vitro, and we identified significant enrichment in G4 sequence motifs at the transcription start site and 5' ends of first introns (false discovery rate < 0.001) of genes down-regulated in WS patient fibroblasts. This finding provides strong evidence that WRN binds G4 DNA structures at many chromosomal sites to modulate gene expression. WRN appears to bind a distinct subpopulation of G4 motifs in human cells, when compared with the related Bloom syndrome RECQ helicase protein. Functional annotation of the genes and miRNAs altered in WS provided new insight into WS disease pathogenesis. WS patient fibroblasts displayed altered expression of multiple, mechanistically distinct, senescence-associated gene expression programs, with altered expression of disease-associated miRNAs, and dysregulation of canonical pathways that regulate cell signaling, genome stability and tumorigenesis. WS fibroblasts also displayed a highly statistically significant and distinct gene expression signature, with coordinate overexpression of nearly all of the cytoplasmic tRNA synthetases and associated ARS-interacting multifunctional protein genes. The 'non-canonical' functions of many of these upregulated tRNA charging proteins may together promote WS disease pathogenesis. Our results identify the human WRN RECQ protein as a G4 helicase that modulates gene expression in G4-dependent fashion at many chromosomal sites and provide several new and unexpected mechanistic insights into WS disease pathogenesis.

Identification of RECQ1-regulated transcriptome uncovers a role of RECQ1 in regulation of cancer cell migration and invasion

The RECQ protein family of helicases has critical roles in protecting and stabilizing the genome. Three of the 5 known members of the human RecQ family are genetically linked with cancer susceptibility syndromes, but the association of the most abundant human RecQ homolog, RECQ1, with cellular transformation is yet unclear. RECQ1 is overexpressed in a variety of human cancers, indicating oncogenic functions. Here, we assessed genome-wide changes in gene expression upon knockdown of RECQ1 in HeLa and MDA-MB-231 cells. Pathway analysis suggested that RECQ1 enhances the expression of multiple genes that play key roles in cell migration, invasion, and metastasis, including EZR, ITGA2, ITGA3, ITGB4, SMAD3, and TGFBR2. Consistent with these results, silencing RECQ1 significantly reduced cell migration and invasion. In comparison to genome-wide annotated promoter regions, the promoters of genes downregulated upon RECQ1 silencing were significantly enriched for a potential G4 DNA forming sequence motif. Chromatin immunoprecipitation assays demonstrated binding of RECQ1 to the G4 motifs in the promoters of select genes downregulated upon RECQ1 silencing. In breast cancer patients, the expression of a subset of RECQ1-activated genes positively correlated with RECQ1 expression. Moreover, high RECQ1 expression was associated with poor prognosis in breast cancer. Collectively, our findings identify a novel function of RECQ1 in gene regulation and indicate that RECQ1 contributes to tumor development and progression, in part, by regulating the expression of key genes that promote cancer cell migration, invasion and metastasis.

The Werner Protein Acts as a Coactivator of Nuclear Factor κB (NF-κB) on HIV-1 and Interleukin-8 (IL-8) Promoters

The Werner syndrome helicase (WRN) plays a role in maintaining genomic stability. The lack of WRN results in Werner syndrome, a rare autosomal recessive genetic disorder, which causes premature aging accompanied by many complications such as rare forms of cancer and type 2 diabetes. However, the underlying mechanisms of these complications, arising due to the loss of WRN, are poorly understood. In this study, we demonstrated the function of WRN in transcriptional regulation of NF-κB targets. WRN physically interacts via its RecQ C-terminal (RQC) domain with the Rel homology domain of both the RelA (p65) and the p50 subunits of NF-κB. In the steady state, WRN is recruited to HIV-1 long terminal repeat (LTR), a typical NF-κB-responsive promoter, as well as the p50/p50 homodimer, in an NF-κB site-dependent manner. The amount of WRN on LTR increased along with the transactivating RelA/p50 heterodimer in response to TNF-α stimulation. Further, a knockdown of WRN reduced the transactivation of LTR in exogenous RelA/p50-introduced or TNF-α-stimulated cells. Additionally, knockdown of WRN reduced TNF-α stimulation-induced activation of the endogenous promoter of IL-8, an NF-κB-responsive gene, and WRN increased its association with the IL-8 promoter region together with RelA/p50 after TNF-α stimulation. In conjunction with studies that have shown NF-κB to be a key regulator of aging and inflammation, our results indicate a novel role of WRN in transcriptional regulation. Along with NF-κB, the loss of WRN is expected to result in incorrect regulation of downstream targets and leads to immune abnormalities and homeostatic disruption.

"...Rewritten in the skin": clues to skin biology and aging from inherited disease

The growing diversity of heritable skin diseases, a practical challenge to clinicians and dermato-nosologists alike, has nonetheless served as a rich source of insight into skin biology and disease mechanisms. I summarize below some key insights from the recent gene-driven phase of research on Werner syndrome, a heritable adult progeroid syndrome with prominent dermatologic features, constitutional genomic instability, and an elevated risk of cancer. I also indicate how new insights into skin biology, disease, and aging may come from unexpected sources.

Age-related decrease of IF5/BTG4 in oral and respiratory cavities in mice

An IF5 cDNA was isolated by expression cloning from a mouse oocyte cDNA library. It encoded a protein of 250 amino acids, and the region of it encoding amino acids 1-137 showed 86.8% alignment with the anti-proliferative domain of BTG/TOB family genes. This gene is also termed BTG4 or PC3B. Transiently expressed IF5/BTG4 induced alkaline phosphatase activity in human embryonic kidney (HEK293T) and 2T3 cells. IF5/BTG4 mRNA was detected by reverse transcription polymerase chain reaction in pharynx, larynx, trachea, oviduct, ovary, caput epididymis, and testis, but not in lung, intestine, or liver. Immunohistochemistry showed the IF5/BTG4 protein to be present in epithelial cells of the tongue, palate, pharynx, internal nose, and trachea. Both protein and mRNA levels of IF5/BTG4 were reduced by aging when comparing 4-week-old mice with 48-week-old mice. Our findings suggest that IF5/BTG4 may be an aging-related gene in epithelial cells.

Transient overexpression of Werner protein rescues starvation induced autophagy in Werner syndrome cells

Reduced autophagy may be associated with normal and pathological aging. Here we report a link between autophagy and Werner protein (WRNp), mutated in Werner syndrome, the human premature aging Werner syndrome (WS). WRN mutant fibroblast AG11395 and AG05229 respond weakly to starvation induced autophagy compared to normal cells. While the fusion of phagosomes with lysosome is normal, WS cells contain fewer autophagy vacuoles. Cellular starvation autophagy in WS cells is restored after transfection with full length WRN. Further, siRNA mediated silencing of WRN in the normal fibroblast cell line WI-38 results in decreased autophagy and altered expression of autophagy related proteins. Thus, our observations suggest that WRN may have a role in controlling autophagy and hereby cellular maintenance.

WITHDRAWN: Systems Biology and Immune Aging

The Publisher regrets that this article is an accidental duplication of anarticle that has already been published, http://dx.doi.org/10.1016/j.imlet.2014.09.009. The duplicate article has therefore been withdrawn.

Werner syndrome protein positively regulates XRCC4-like factor transcription

XRCC4-like factor (XLF) is involved in non-homologous end joining-mediated repair of DNA double-strand breaks (DSBs). Mutations in the WRN gene results in the development of Werner syndrome (WS), a rare autosomal recessive disorder characterized by premature ageing and genome instability. In the present study, it was identified that XLF protein levels were lower in WRN-deficient fibroblasts, compared with normal fibroblasts. Depletion of WRN in HeLa cells led to a decrease of XLF mRNA and its promoter activity. Chromatin immunoprecipitation assays demonstrated that WRN was associated with the XLF promoter. Depletion of XLF in normal human fibroblasts increased the percentage of β-galactosidase (β-gal) staining-positive cells, indicating acceleration in cellular senescence. Taken together, the results suggest that XLF is a transcriptional target of WRN and may be involved in the regulation of cellular senescence.

Autophagy drives epidermal deterioration in a Drosophila model of tissue aging

Organismal lifespan has been the primary readout in aging research. However, how longevity genes control tissue-specific aging remains an open question. To examine the crosstalk between longevity programs and specific tissues during aging, biomarkers of organ-specific aging are urgently needed. Since the earliest signs of aging occur in the skin, we sought to examine skin aging in a genetically tractable model. Here we introduce a Drosophila model of skin aging. The epidermis undergoes a dramatic morphological deterioration with age that includes membrane and nuclear loss. These changes were decelerated in a long-lived mutant and accelerated in a short-lived mutant. An increase in autophagy markers correlated with epidermal aging. Finally, the epidermis of Atg7 mutants retained younger characteristics, suggesting that autophagy is a critical driver of epidermal aging. This is surprising given that autophagy is generally viewed as protective during aging. Since Atg7 mutants are short-lived, the deceleration of epidermal aging in this mutant suggests that in the epidermis healthspan can be uncoupled from longevity. Because the aging readout we introduce here has an early onset and is easily visualized, genetic dissection using our model should identify other novel mechanisms by which lifespan genes feed into tissue-specific aging.

Omics technologies and the study of human ageing

Normal ageing is associated with diverse physiological changes in all organ systems but the rate and extent of these changes vary markedly among individuals. One aspect of ageing research focuses on the molecular profiling of the changes that occur with increasing age in humans. Such profiling has implications for disease prevention and treatment. New high-throughput 'omics' technologies (such as genomics, metabolomics, metagenomics and transcriptomics) are enabling detailed studies of these molecular changes and are thus revealing information about the biological pathways that change with age.

Identification of the dichotomous role of age-related LCK in calorie restriction revealed by integrative analysis of cDNA microarray and interactome

Among the many experimental paradigms used for the investigation of aging, the calorie restriction (CR) model has been proven to be the most useful in gerontological research. Exploration of the mechanisms underlying CR has produced a wealth of data. To identify key molecules controlled by aging and CR, we integrated data from 84 mouse and rat cDNA microarrays with a protein-protein interaction network. On the basis of this integrative analysis, we selected three genes that are upregulated in aging but downregulated by CR and two genes that are downregulated in aging but upregulated by CR. One of these key molecules is lymphocyte-specific protein tyrosine kinase (LCK). To further confirm this result on LCK, we performed a series of experiments in vitro and in vivo using kidneys obtained from aged ad libitum-fed and CR rats. Our major significant findings are as follows: (1) identification of LCK as a key molecule using integrative analysis; (2) confirmation that the age-related increase in LCK was modulated by CR and that protein tyrosine kinase activity was decreased using a LCK-specific inhibitor; and (3) upregulation of LCK leads to NF-κB activation in a ONOO(-) generation-dependent manner, which is modulated by CR. These results indicate that LCK could be considered a target attenuated by the anti-aging effects of CR. Integrative analysis of cDNA microarray and interactome data are powerful tools for identifying target molecules that are involved in the aging process and modulated by CR.

Characterizing short stature by insulin-like growth factor axis status and genetic associations: results from the prospective, cross-sectional, epidemiogenetic EPIGROW study

CONTEXT

Serum IGF-I levels are often low in patients with short stature (SS) without defined etiology. Hence, genetic investigations have focused on the GH-IGF-I axis.

OBJECTIVE

Our objectives were to characterize IGF-I axis status and search for a broader range of genetic associations in children with SS and normal GH.

DESIGN AND SETTING

We conducted a prospective, cross-sectional, epidemiogenetic case-control study in 9 European countries (2008-2010).

PARTICIPANTS

Children (n = 275) aged ≥2 years with SS without defined etiology (≤-2.5 height SD score [SDS]) and ≥1 peak GH ≥7 μg/L) were recruited.

METHODS

Serum IGF-I, IGF-binding protein-3 (IGFBP-3), and acid-labile subunit (ALS) levels were measured in a central laboratory. Candidate gene exome sequencing was performed in this cohort and ethnicity-matched controls.

RESULTS

Serum IGF-I, IGFBP-3, and ALS levels were highly correlated, but there was a discrepancy between prevalence of IGF-I, IGFBP-3, and ALS deficiencies (53%, 30%, and 0.8%, respectively). An insertion-deletion (Indel) on the IGF1 gene (P = 1.2 × 10(-5), Bonferroni-corrected; case vs control frequency: 0.04 vs 0.112), an Indel on NFKB1 (P = 1.36 × 10(-10); case vs control frequency: 0.464 vs 0.272), and 2 single-nucleotide polymorphisms on ZBTB38 (P < 2.3 × 10(-6)) were associated with SS. At P < 10(-4), single-nucleotide polymorphisms on genes related to protein kinase regulation, MAPK, and Fanconi pathways were also associated with SS.

CONCLUSIONS

IGF-I deficiency is a common feature in SS without defined etiology; an Indel in the IGF1 gene was associated with SS. However, genes involved in transcriptional regulation (NFKB1 and ZBTB38) and growth factor signaling were also associated, providing further candidates for genetic investigations on individual patients.

Genetics and skin aging

Skin aging is a complex process and underlies multiple influences with the probable involvement of heritable and various environmental factors. Several theories have been conducted regarding the pathomechanisms of aged skin, however fundamental mechanisms still remain poorly understood. This article addresses the influence of genetics on skin aging and in particular deals with the differences observed in ethnic populations and between both genders. Recent studies indicate that male and female aged skin differs as far as the type, the consistency and the sensitivity to external factors is concerned. The same has been also documented between elderly people of different origin. Consequently, the aging process taking place in both genders and in diverse ethnic groups should be examined separately and products specialized to each population should be developed in order to satisfy the special needs.

[Werner syndrome. A prototypical form of segmental progeria.]

Werner syndrome is a segmental progeroid disorder with onset in adolescence or early adulthood. Typical symptoms contributing to patients' prematurely aged appearance include postpubertal development of short stature, cataracts, premature greying/thinning of scalp hair, scleroderma-like skin changes and regional atrophy of subcutaneous fat tissue. In addition, an increased rate and early onset of typical age-related diseases such as type 2 diabetes mellitus, osteoporosis, atherosclerosis, and various malignancies is observed. Werner syndrome is autosomal recessively inherited and caused by mutations in the Werner gene (WRN). To date, more than 70 WRN mutations have been identified. These are spread over the entire gene and typically represent loss of function mutations. WRN encodes a RecQ type helicase involved in DNA repair and the maintenance of DNA integrity, which is reflected by an increased genetic instability in patient cells. Despite the relative rarity of Werner syndrome, its analysis provides important general insights into the roles of DNA stability and integrity for the ageing process and the development of age-associated diseases.

Sporadic Alzheimer disease fibroblasts display an oxidative stress phenotype

Alzheimer disease (AD) is a major health problem in the United States, affecting one in eight Americans over the age of 65. The number of elderly suffering from AD is expected to continue to increase over the next decade, as the average age of the U.S. population increases. The risk factors for and etiology of AD are not well understood; however, recent studies suggest that exposure to oxidative stress may be a contributing factor. Here, microarray gene expression signatures were compared in AD-patient-derived fibroblasts and normal fibroblasts exposed to hydrogen peroxide or menadione (to simulate conditions of oxidative stress). Using the 23K Illumina cDNA microarray to screen expression of >14,000 human genes, we identified a total of 1017 genes that are chronically up- or downregulated in AD fibroblasts, 215 of which were also differentially expressed in normal human fibroblasts within 12h after exposure to hydrogen peroxide or menadione. Pathway analysis of these 215 genes and their associated pathways revealed cellular functions that may be critically dysregulated by oxidative stress and play a critical role in the etiology and/or pathology of AD. We then examined the AD fibroblasts for the presence of oxidative DNA damage and found increased accumulation of 8-oxo-guanine. These results indicate the possible role of oxidative stress in the gene expression profile seen in AD.

Chronic inhibition of the respiratory chain in human fibroblast cultures: differential responses related to subject chronological and biological age

Respiratory chain function becomes less efficient with age resulting in increased levels of damaging reactive oxygen species. We compared rotenone-exposed fibroblast strains from young and old subjects and from offspring of nonagenarian siblings and the partners of the offspring. Rotenone increased reactive oxygen species levels, inhibited growth rate, and increased telomere shortening (all p < .05). Non-stressed strains from young subjects showed lower reactive oxygen species levels (p = .031) and higher growth rates (p = .002) than strains from old subjects. Stressed strains from young subjects showed smaller increases in reactive oxygen species levels (p = .014) and larger decreases in growth rate (p < .001) than strains from old subjects. Telomere-shortening rates were not different between groups. Stress-induced decreases in growth rate were larger in strains from offspring than from partners (p = .05). Strains from young and old subjects are differentially affected by chronic inhibition of the respiratory chain. Changed growth rates in strains from offspring resemble those from strains from young subjects.

Gene expression levels assessed by CA1 pyramidal neuron and regional hippocampal dissections in Alzheimer's disease

To evaluate molecular signatures of an individual cell type in comparison to the associated region relevant towards understanding the pathogenesis of Alzheimer's disease (AD), CA1 pyramidal neurons and the surrounding hippocampal formation were microaspirated via laser capture microdissection (LCM) from neuropathologically confirmed AD and age-matched control (CTR) subjects as well as from wild type mouse brain using single population RNA amplification methodology coupled with custom-designed microarray analysis with real-time quantitative polymerase-chain reaction (qPCR) validation. CA1 pyramidal neurons predominantly displayed downregulation of classes of transcripts related to synaptic transmission in AD versus CTR. Regional hippocampal dissections displayed downregulation of several overlapping genes found in the CA1 neuronal population related to neuronal expression, as well as upregulation of select transcripts indicative of admixed cell types including glial-associated markers and immediate-early and cell death genes. Gene level distributions observed in CA1 neurons and regional hippocampal dissections in wild type mice paralleled expression mosaics seen in postmortem human tissue. Microarray analysis was validated in qPCR studies using human postmortem brain tissue and CA1 sector and regional hippocampal dissections obtained from a mouse model of AD/Down syndrome (Ts65Dn mice) and normal disomic (2N) littermates. Classes of transcripts that have a greater percentage of the overall hybridization signal intensity within single neurons tended to be genes related to neuronal communication. The converse was also found, as classes of transcripts such as glial-associated markers were under represented in CA1 pyramidal neuron expression profiles relative to regional hippocampal dissections. These observations highlight a dilution effect that is likely to occur in conventional regional microarray and qPCR studies. Thus, single population studies of specific neurons and intrinsic circuits will likely yield informative gene expression profile data that may be subthreshold and/or underrepresented in regional studies with an admixture of cell types.

[Molecular etiology of skin aging. How important is the genetic make-up?]

Although the fundamental mechanisms in the pathogenesis of skin aging are still poorly understood, a growing body of evidence points toward the involvement of multiple pathways. Recent data obtained by expression profiling studies and studies upon progeroid syndromes illustrate that among the most important biological processes involved in skin aging are alterations in DNA repair and stability, mitochondrial function, cell cycle and apoptosis, extracellular matrix, lipid synthesis, ubiquitin-induced proteolysis and cellular metabolism. One of the major factors which have been proposed to play an exquisite role in the initiation of aging is the physiological decline of hormones occurring with age. However, hormones at age-specific levels may not only regulate age-associated mechanisms but also modulate tumor suppressor pathways that influence carcinogenesis. In conclusion, understanding the molecular mechanisms of ageing may open new strategies to deal with the various diseases accompanying advanced age including cancer.

Clinical aspects and molecular diagnostics of skin aging

This contribution will address the effect of aging on skin functions, with a particular focus on skin permeability, wound healing, angiogenesis, lipogenesis, sweat production, immune function, and vitamin D synthesis. With accelerating age, skin functions deteriorate due to structural and morphologic changes. Skin is prone to the development of several diseases, varying from benign to malignant. Because the number of persons aged 80 and older is expected to rise in the next decades, disease prevention will become an important issue. Screening examinations and prevention through public education starting at an early age regarding sun avoidance, the use of sunscreens and the importance of a balanced nutrition are the first steps for successful healthy aging. Although the fundamental mechanisms in the pathogenesis of aged skin are still poorly understood, a growing body of evidence points toward the involvement of multiple pathways. Recent data obtained by expression profiling studies and studies of progeroid syndromes illustrate that among the most important biologic processes involved in skin aging are alterations in DNA repair and stability, mitochondrial function, cell cycle and apoptosis, extracellular matrix, lipid synthesis, ubiquitin-induced proteolysis and cellular metabolism. Among others, a major factor that has been implicated in the initiation of aging is the physiologic decline of hormones occurring with age. However, hormones at age-specific levels may regulate not only age-associated mechanisms but also tumor suppressor pathways that influence carcinogenesis. Understanding the molecular mechanisms of aging may open new strategies to deal with the various diseases accompanying high age, including cancer.

Non-B DNA-forming sequences and WRN deficiency independently increase the frequency of base substitution in human cells

Although alternative DNA secondary structures (non-B DNA) can induce genomic rearrangements, their associated mutational spectra remain largely unknown. The helicase activity of WRN, which is absent in the human progeroid Werner syndrome, is thought to counteract this genomic instability. We determined non-B DNA-induced mutation frequencies and spectra in human U2OS osteosarcoma cells and assessed the role of WRN in isogenic knockdown (WRN-KD) cells using a supF gene mutation reporter system flanked by triplex- or Z-DNA-forming sequences. Although both non-B DNA and WRN-KD served to increase the mutation frequency, the increase afforded by WRN-KD was independent of DNA structure despite the fact that purified WRN helicase was found to resolve these structures in vitro. In U2OS cells, ∼70% of mutations comprised single-base substitutions, mostly at G·C base-pairs, with the remaining ∼30% being microdeletions. The number of mutations at G·C base-pairs in the context of NGNN/NNCN sequences correlated well with predicted free energies of base stacking and ionization potentials, suggesting a possible origin via oxidation reactions involving electron loss and subsequent electron transfer (hole migration) between neighboring bases. A set of ∼40,000 somatic mutations at G·C base pairs identified in a lung cancer genome exhibited similar correlations, implying that hole migration may also be involved. We conclude that alternative DNA conformations, WRN deficiency and lung tumorigenesis may all serve to increase the mutation rate by promoting, through diverse pathways, oxidation reactions that perturb the electron orbitals of neighboring bases. It follows that such "hole migration" is likely to play a much more widespread role in mutagenesis than previously anticipated.

The nucleolus

When cells are observed by phase contrast microscopy, nucleoli are among the most conspicuous structures. The nucleolus was formally described between 1835 and 1839, but it was another century before it was discovered to be associated with a specific chromosomal locus, thus defining it as a cytogenetic entity. Nucleoli were first isolated in the 1950s, from starfish oocytes. Then, in the early 1960s, a boomlet of studies led to one of the epochal discoveries in the modern era of genetics and cell biology: that the nucleolus is the site of ribosomal RNA synthesis and nascent ribosome assembly. This epistemologically repositioned the nucleolus as not merely an aspect of nuclear anatomy but rather as a cytological manifestation of gene action-a major heuristic advance. Indeed, the finding that the nucleolus is the seat of ribosome production constitutes one of the most vivid confluences of form and function in the history of cell biology. This account presents the nucleolus in both historical and contemporary perspectives. The modern era has brought the unanticipated discovery that the nucleolus is plurifunctional, constituting a paradigm shift.

Splice variants of the dual specificity tyrosine phosphorylation-regulated kinase 4 (DYRK4) differ in their subcellular localization and catalytic activity

Dual specificity tyrosine phosphorylation-regulated kinases, DYRKs, are a family of conserved protein kinases that play key roles in the regulation of cell differentiation, proliferation, and survival. Of the five mammalian DYRKs, DYRK4 is the least studied family member. Here, we show that several splice variants of DYRK4 are expressed in tissue-specific patterns and that these variants have distinct functional capacities. One of these variants contains a nuclear localization signal in its extended N terminus that mediates its interaction with importin α3 and α5 and that is capable of targeting a heterologous protein to the nucleus. Consequently, the nucleocytoplasmic mobility of this variant differs from that of a shorter isoform in live cell imaging experiments. Other splicing events affect the catalytic domain, including a three-amino acid deletion within subdomain XI that markedly reduces the enzymatic activity of DYRK4. We also show that autophosphorylation of a tyrosine residue within the activation loop is necessary for full DYRK4 kinase activity, a defining feature of the DYRK family. Finally, by comparing the phosphorylation of an array of 720 peptides, we show that DYRK1A, DYRK2, and DYRK4 differ in their target recognition sequence and that preference for an arginine residue at position P -3 is a feature of DYRK1A but not of DYRK2 and DYRK4. Therefore, we highlight the use of subcellular localization as an important regulatory mechanism for DYRK proteins, and we propose that substrate specificity could be a source of functional diversity among DYRKs.

Proteome-wide identification of WRN-interacting proteins in untreated and nuclease-treated samples

Werner syndrome (WS) is characterized by the premature onset of several age-associated pathologies. The protein defective in WS patients (WRN) is a helicase/exonuclease involved in DNA repair, replication, telomere maintenance, and transcription. Here, we present the results of a large-scale proteome analysis to determine protein partners of WRN. We expressed fluorescent tagged-WRN (eYFP-WRN) in human 293 embryonic kidney cells and detected interacting proteins by co-immunoprecipitation from cell extract. We identified by mass spectrometry 220 nuclear proteins that complexed with WRN. This number was reduced to 40 when broad-spectrum nucleases were added to the lysate. We consider these 40 proteins as directly interacting with WRN. Some of these proteins have previously been shown to interact with WRN, whereas most are new partners. Among the top 15 hits, we find the new interactors TMPO, HNRNPU, RPS3, RALY, RPS9 DDX21, and HNRNPM. These proteins are likely important components in understanding the function of WRN in preventing premature aging and deserve further investigation. We have confirmed endogenous WRN interaction with endogenous RPS3, a ribosomal protein with endonuclease activities involved in oxidative DNA damage recognition. Our results suggest that the use of nucleases during cell lysis severely restricts interacting protein partners and thus enhances specificity.

Studies of complex biological systems with applications to molecular medicine: the need to integrate transcriptomic and proteomic approaches

Omics approaches to the study of complex biological systems with potential applications to molecular medicine are attracting great interest in clinical as well as in basic biological research. Genomics, transcriptomics and proteomics are characterized by the lack of an a priori definition of scope, and this gives sufficient leeway for investigators (a) to discern all at once a globally altered pattern of gene/protein expression and (b) to examine the complex interactions that regulate entire biological processes. Two popular platforms in "omics" are DNA microarrays, which measure messenger RNA transcript levels, and proteomic analyses, which identify and quantify proteins. Because of their intrinsic strengths and weaknesses, no single approach can fully unravel the complexities of fundamental biological events. However, an appropriate combination of different tools could lead to integrative analyses that would furnish new insights not accessible through one-dimensional datasets. In this review, we will outline some of the challenges associated with integrative analyses relating to the changes in metabolic pathways that occur in complex pathophysiological conditions (viz. ageing and altered thyroid state) in relevant metabolically active tissues. In addition, we discuss several new applications of proteomic analysis to the investigation of mitochondrial activity.

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.

Mitochondrial dysfunction in some oxidative stress-related genetic diseases: Ataxia-Telangiectasia, Down Syndrome, Fanconi Anaemia and Werner Syndrome

Oxidative stress is a phenotypic hallmark in several genetic disorders characterized by cancer predisposition and/or propensity to premature ageing. Here we review the published evidence for the involvement of oxidative stress in the phenotypes of Ataxia-Telangiectasia (A-T), Down Syndrome (DS), Fanconi Anaemia (FA), and Werner Syndrome (WS), from the viewpoint of mitochondrial dysfunction. Mitochondria are recognized as both the cell compartment where energetic metabolism occurs and as the first and most susceptible target of reactive oxygen species (ROS) formation. Thus, a critical evaluation of the basic mechanisms leading to an in vivo pro-oxidant state relies on elucidating the features of mitochondrial impairment in each disorder. The evidence for different mitochondrial dysfunctions reported in A-T, DS, and FA is reviewed. In the case of WS, clear-cut evidence linking human WS phenotype to mitochondrial abnormalities is lacking so far in the literature. Nevertheless, evidence relating mitochondrial dysfunctions to normal ageing suggests that WS, as a progeroid syndrome, is likely to feature mitochondrial abnormalities. Hence, ad hoc research focused on elucidating the nature of mitochondrial dysfunction in WS pathogenesis is required. Based on the recognized, or reasonably suspected, role of mitochondrial abnormalities in the pathogenesis of these disorders, studies of chemoprevention with mitochondria-targeted supplements are warranted.

Roles of Werner syndrome protein in protection of genome integrity

Werner syndrome protein (WRN) is one of a family of five human RecQ helicases implicated in the maintenance of genome stability. The conserved RecQ family also includes RecQ1, Bloom syndrome protein (BLM), RecQ4, and RecQ5 in humans, as well as Sgs1 in Saccharomyces cerevisiae, Rqh1 in Schizosaccharomyces pombe, and homologs in Caenorhabditis elegans, Xenopus laevis, and Drosophila melanogaster. Defects in three of the RecQ helicases, RecQ4, BLM, and WRN, cause human pathologies linked with cancer predisposition and premature aging. Mutations in the WRN gene are the causative factor of Werner syndrome (WS). WRN is one of the best characterized of the RecQ helicases and is known to have roles in DNA replication and repair, transcription, and telomere maintenance. Studies both in vitro and in vivo indicate that the roles of WRN in a variety of DNA processes are mediated by post-translational modifications, as well as several important protein-protein interactions. In this work, we will summarize some of the early studies on the cellular roles of WRN and highlight the recent findings that shed some light on the link between the protein with its cellular functions and the disease pathology.

Altered gene expression in the Werner and Bloom syndromes is associated with sequences having G-quadruplex forming potential

The human Werner and Bloom syndromes (WS and BS) are caused by deficiencies in the WRN and BLM RecQ helicases, respectively. WRN, BLM and their Saccharomyces cerevisiae homologue Sgs1, are particularly active in vitro in unwinding G-quadruplex DNA (G4-DNA), a family of non-canonical nucleic acid structures formed by certain G-rich sequences. Recently, mRNA levels from loci containing potential G-quadruplex-forming sequences (PQS) were found to be preferentially altered in sgs1Δ mutants, suggesting that G4-DNA targeting by Sgs1 directly affects gene expression. Here, we extend these findings to human cells. Using microarrays to measure mRNAs obtained from human fibroblasts deficient for various RecQ family helicases, we observe significant associations between loci that are upregulated in WS or BS cells and loci that have PQS. No such PQS associations were observed for control expression datasets, however. Furthermore, upregulated genes in WS and BS showed no or dramatically reduced associations with sequences similar to PQS but that have considerably reduced potential to form intramolecular G4-DNA. These findings indicate that, like Sgs1, WRN and BLM can regulate transcription globally by targeting G4-DNA.

Vitamin C restores healthy aging in a mouse model for Werner syndrome

Werner syndrome (WS) is a premature aging disorder caused by mutations in a RecQ-like DNA helicase. Mice lacking the helicase domain of the WRN homologue exhibit many phenotypic features of WS, including a prooxidant status and a shorter mean life span compared to wild-type animals. Here, we show that Wrn mutant mice also develop premature liver sinusoidal endothelial defenestration along with inflammation and metabolic syndrome. Vitamin C supplementation rescued the shorter mean life span of Wrn mutant mice and reversed several age-related abnormalities in adipose tissues and liver endothelial defenestration, genomic integrity, and inflammatory status. At the molecular level, phosphorylation of age-related stress markers like Akt kinase-specific substrates and the transcription factor NF-kappaB, as well as protein kinase Cdelta and Hif-1alpha transcription factor levels, which are increased in the liver of Wrn mutants, were normalized by vitamin C. Vitamin C also increased the transcriptional regulator of lipid metabolism PPARalpha. Finally, microarray and gene set enrichment analyses on liver tissues revealed that vitamin C decreased genes normally up-regulated in human WS fibroblasts and cancers, and it increased genes involved in tissue injury response and adipocyte dedifferentiation in obese mice. Vitamin C did not have such effect on wild-type mice. These results indicate that vitamin C supplementation could be beneficial for patients with WS.

Werner's syndrome helicase participates in transcription of phenobarbital-inducible CYP2B genes in rat and mouse liver

Werner's syndrome (WS) is a rare human autosomal recessive segmental progeroid syndrome clinically characterized by atherosclerosis, cancer, osteoporosis, type 2 diabetes mellitus and ocular cataracts. The WRN gene codes for a RecQ helicase which is present in many tissues. Although the exact functions of the WRN protein remain unclear, accumulating evidence suggests that it participates in DNA repair, replication, recombination and telomere maintenance. It has also been proposed that WRN participates in RNA polymerase II-dependent transcription. However no promoter directly targeted by WRN has yet been identified. In this work, we report mammalian genes that are WRN targets. The rat CYP2B2 gene and its closely related mouse homolog, Cyp2b10, are both strongly induced in liver by phenobarbital. We found that there is phenobarbital-dependent recruitment of WRN to the promoter of the CYP2B2 gene as demonstrated by chromatin immunoprecipitation analysis. Mice homozygous for a Wrn mutation deleting part of the helicase domain showed a decrease in basal and phenobarbital-induced CYP2B10 mRNA levels compared to wild type animals. The phenobarbital-induced level of CYP2B10 protein was also reduced in the mutant mice. Electrophoretic mobility shift assays showed that WRN can participate in the formation of a complex with a specific sequence within the CYP2B2 basal promoter. Hence, there is a WRN binding site in a region of DNA sequence to which WRN is recruited in vivo. Taken together, these results suggest that WRN participates in transcription of CYP2B genes in liver and identifies the first physical interaction between a specific promoter sequence and WRN.

Gene expression changes in normal haematopoietic cells

The complexity of the healthy haematopoietic system is immense, and as such, one must understand the biology driving normal haematopoietic expression profiles when designing experiments and interpreting expression data that involve normal cells. This article seeks to present an organised approach to the use and interpretation of gene profiling in normal haematopoiesis and broadly illustrates the challenges of selecting appropriate controls for high-throughput expression studies.