Histone Ubiquitination by the DNA Damage Response Is Required for Efficient DNA Replication in Unperturbed S Phase.

Chromatin ubiquitination by the ubiquitin ligase RNF168 is critical to regulate the DNA damage response (DDR). DDR deficiencies lead to cancer-prone syndromes, but whether this reflects DNA repair defects is still elusive. We identified key factors of the RNF168 pathway as essential mediators of efficient DNA replication in unperturbed S phase. We found that loss of RNF168 leads to reduced replication fork progression and to reversed fork accumulation, particularly evident at repetitive sequences stalling replication. Slow fork progression depends on MRE11-dependent degradation of reversed forks, implicating RNF168 in reversed fork protection and restart. Consistent with regular nucleosomal organization of reversed forks, the replication function of RNF168 requires H2A ubiquitination. As this novel function is shared with the key DDR players ATM, γH2A.X, RNF8, and 53BP1, we propose that double-stranded ends at reversed forks engage classical DDR factors, suggesting an alternative function of this pathway in preventing genome instability and human disease.

PDGFRß and oncogenic mutant PDGFRα D842V promote disassembly of primary cilia through a PLCγ- and AURKA-dependent mechanism.

Primary cilia are microtubule-based sensory organelles projecting from most quiescent mammalian cells, which disassemble in cells cultured in serum-deprived conditions upon re-addition of serum or growth factors. Platelet-derived growth factors (PDGF) are implicated in deciliation, but the specific receptor isoforms and mechanisms involved are unclear. We report that PDGFRß promotes deciliation in cultured cells and provide evidence implicating PLCγ and intracellular Ca(2+) release in this process. Activation of wild-type PDGFRα alone did not elicit deciliation. However, expression of constitutively active PDGFRα D842V mutant receptor, which potently activates PLCγ (also known as PLCG1), caused significant deciliation, and this phenotype was rescued by inhibiting PDGFRα D842V kinase activity or AURKA. We propose that PDGFRß and PDGFRα D842V promote deciliation through PLCγ-mediated Ca(2+) release from intracellular stores, causing activation of calmodulin and AURKA-triggered deciliation.

Biological evaluation of pyridone alkaloids on the endocannabinoid system.

Naturally occurring pyridone alkaloids as well as synthetic derivatives were previously shown to induce neurite outgrowth. However, the molecular basis for this biological effect remains poorly understood. In this work, we have prepared new pyridones, and tested the effect of thirteen 4-hydroxy-2-pyridone derivatives on the components of the endocannabinoid system. Investigation of binding affinities towards CB1 and CB2 receptors led to the identification of a compound binding selectively to CB1 (12). Compound 12 and a closely related derivative (11) also inhibited anandamide (AEA) hydrolysis by fatty acid amide hydrolase. Interestingly, none of the compounds tested showed any effect on 2-AG hydrolysis by monoacylglycerol lipase at 10µM. Assessment of AEA uptake did, however, lead to the identification of four inhibitors with IC50 values in the submicromolar range and high selectivity over the other components of the endocannabinoid system.

Truncated borrelidin analogues: synthesis by sequential cross metathesis/olefination for the southern fragment and biological evaluation.

The construction of novel borrelidin analogues is reported in which the northern fragment is truncated to a simple hydroxyundecanecarboxylate and the original cyclopentanecarboxylic acid in the southern fragment is replaced with different six-membered rings. The required precursors were prepared by cross metathesis of the appropriate carbocycle-based homoallylic alcohol with crotonaldehyde followed by HWE olefination of the resulting enal with bromocyanophosphonate. The key aldehyde for intramolecular cross coupling was accessible by oxidation of the hydroxy group of the linked undecanecarboxylate unit. Grignard mediated macrocyclization finally yielded the borrelidin related products. The investigation is complemented by SAR studies and quantum-chemical calculations.

Nanodroplet Flight Control in Electrohydrodynamic Redox 3D Printing.

Electrohydrodynamic 3D printing is an additive manufacturing technique with enormous potential in plasmonics, microelectronics, and sensing applications thanks to its broad material palette, high voxel deposition rate, and compatibility with various substrates. However, the electric field used to deposit material is concentrated at the depositing structure, resulting in the focusing of the charged droplets and geometry-dependent landing positions, which complicates the fabrication of complex 3D shapes. The low level of concordance between the design and printout seriously impedes the development of electrohydrodynamic 3D printing and rationalizes the simplicity of the designs reported so far. In this work, we break the electric field centrosymmetry to study the resulting deviation in the flight trajectory of the droplets. Comparison of experimental outcomes with predictions of an FEM model provides new insights into the droplet characteristics and unveils how the product of droplet size and charge uniquely governs its kinematics. From these insights, we develop reliable predictions of the jet trajectory and allow the computation of optimized printing paths counterbalancing the electric field distortion, thereby enabling the fabrication of geometries with unprecedented complexity.

Gene therapeutic approach using mutation-adapted U1 snRNA to correct a RPGR splice defect in patient-derived cells.

Retinitis pigmentosa (RP) is a disease that primarily affects the peripheral retina and ultimately causes visual impairment. X-chromosomal forms of RP are frequently caused by mutations in the retinitis pigmentosa GTPase regulator (RPGR) gene. We show that the novel splice donor site (SDS) mutation c.1245+3A>T in intron 10 of RPGR cosegregates with RP in a five-generation Caucasian family. The mutation causes in-frame skipping of exon 10 from RPGR transcripts in patient-derived primary fibroblasts. To correct the splice defect, we developed a gene therapeutic approach using mutation-adapted U1 small nuclear RNA (U1). U1 is required for SDS recognition of pre-mRNAs and initiates the splice process. The mutation described herein interferes with the recognition of the SDS by U1. To overcome the deleterious effects of the mutation, we generated four U1 isoforms with increasing complementarity to the SDS. Lentiviral particles were used to transduce patient-derived fibroblasts with these U1 variants. Full complementarity of U1 corrects the splice defect partially and increases recognition of the mutant SDS. The therapeutic effect is U1-concentration dependent as we show for endogenously expressed RPGR transcripts in patient-derived cells. U1-based gene therapeutic approaches constitute promising technologies to treat SDS mutations in inherited diseases including X-linked RP.

U1 snRNA-mediated gene therapeutic correction of splice defects caused by an exceptionally mild BBS mutation.

Bardet-Biedl syndrome (BBS) is a multisystem disorder caused by ciliary defects. To date, mutations in 15 genes have been associated with the disease and BBS1 is most frequently affected in patients with BBS. The use of homozygosity mapping in a large consanguineous family allowed us to identify the splice donor site (SD) mutation c.479G>A in exon 5 of BBS1. Clinically affected family members show symptoms of retinitis pigmentosa (RP) but lack other primary features that would clearly support the diagnosis of BBS. In agreement with this exceptionally mild BBS1-associated phenotype, we did not detect obvious ciliary defects in patient-derived cells. SDs are bound by the U1 small nuclear RNA (U1), a process that initiates exon recognition during splicing. The mutation described herein interferes with U1 binding and induces aberrant splicing of BBS1. For a gene therapeutic approach, we have adapted the sequence of U1 to increase its complementarity to the mutated SD. Lentiviral treatment of patient-derived fibroblasts with the adapted U1 partially corrected aberrant splicing of endogenously expressed BBS1 transcripts. This therapeutic effect was dose-dependent. Our results show that the adaptation of U1 can correct pathogenic effects of splice donor site mutations and suggest a high potential for gene therapy.

Post-challenge hyperglycaemia is strongly associated with future macrovascular events and total mortality in angiographied coronary patients.

AIMS: The prevalence of post-challenge hyperglycaemia in coronary patients is high. Until now, it is unclear whether post-challenge hyperglycaemia is associated with an increased risk for future macrovascular events in this clinically important patient population. METHODS AND RESULTS: We enrolled 1040 patients undergoing coronary angiography for the evaluation of suspected or established coronary artery disease. In patients without previously established diabetes mellitus, an oral glucose tolerance test (oGTT) was performed. Prospectively, mortality and macrovascular events were recorded over a mean follow-up period of 3.8 years. From our patients, 394 had normal glucose tolerance (NGT), 280 post-challenge hyperglycaemia (this subgroup includes both impaired glucose tolerance and post-challenge diabetes) and 366 had conventional diabetes. The incidence of macrovascular events was significantly higher in patients with post-challenge hyperglycaemia as well as in patients with conventional diabetes than in subjects with NGT (23.6 and 29.5% vs. 18.5%; P = 0.013 and P < 0.001, respectively). Adjusted hazard ratios were 1.46 (95% CI 1.03-2.07, P = 0.033) for patients with post-challenge hyperglycaemia and 1.73 (1.25-2.37, P = 0.001) for patients with conventional diabetes. CONCLUSION: Post-challenge hyperglycaemia is associated with future macrovascular events in patients undergoing coronary angiography for the evaluation of stable coronary artery disease (CAD). Oral glucose tolerance tests in this high-risk population thus identify patients with a particularly unfavourable prognosis.

Diabetes as a coronary artery disease risk equivalent: before a change of paradigm?

BACKGROUND: Current guidelines consider diabetes per se as a coronary artery disease (CAD) risk equivalent. We aimed at investigating the contribution of baseline coronary atherosclerosis to the risk of diabetic patients for future vascular events. DESIGN: Prospective cohort study. METHODS: Vascular events were recorded over 4 years in 750 consecutive patients undergoing coronary angiography for the evaluation of stable CAD. RESULTS: From our patients, 244 had neither type 2 diabetes (T2DM) nor significant CAD (i.e. coronary stenoses >or=50%) at the baseline angiography, 50 had T2DM but not significant CAD, 342 did not have T2DM but had significant CAD, and 114 had both T2DM and significant CAD. Nondiabetic patients without significant CAD had an event rate of 9.0%. The event rate was similar in T2DM patients without significant CAD (8.0%, P = 0.951), but higher in nondiabetic patients with significant CAD (24.9%, P<0.001). Patients with T2DM and significant CAD had the highest event rate (43.0%). Importantly, T2DM patients without significant CAD had a significantly lower event rate than nondiabetic patients with significant CAD (P = 0.008). CONCLUSION: T2DM per se is not a CAD risk equivalent. Moderate-risk diabetic patients without significant CAD and very high-risk diabetic patients with significant CAD add up to a grand total of high-risk diabetic patients, this is why diabetes seems to be a CAD risk equivalent in many epidemiological studies.

Interferon-stimulated gene 15 accelerates replication fork progression inducing chromosomal breakage.

DNA replication is highly regulated by the ubiquitin system, which plays key roles upon stress. The ubiquitin-like modifier ISG15 (interferon-stimulated gene 15) is induced by interferons, bacterial and viral infection, and DNA damage, but it is also constitutively expressed in many types of cancer, although its role in tumorigenesis is still largely elusive. Here, we show that ISG15 localizes at the replication forks, in complex with PCNA and the nascent DNA, where it regulates DNA synthesis. Indeed, high levels of ISG15, intrinsic or induced by interferon-ß, accelerate DNA replication fork progression, resulting in extensive DNA damage and chromosomal aberrations. This effect is largely independent of ISG15 conjugation and relies on ISG15 functional interaction with the DNA helicase RECQ1, which promotes restart of stalled replication forks. Additionally, elevated ISG15 levels sensitize cells to cancer chemotherapeutic treatments. We propose that ISG15 up-regulation exposes cells to replication stress, impacting genome stability and response to genotoxic drugs.

Identification of novel mutations in X-linked retinitis pigmentosa families and implications for diagnostic testing.

PURPOSE: The goal of this study was to identify mutations in X-chromosomal genes associated with retinitis pigmentosa (RP) in patients from Germany, The Netherlands, Denmark, and Switzerland. METHODS: In addition to all coding exons of RP2, exons 1 through 15, 9a, ORF15, 15a and 15b of RPGR were screened for mutations. PCR products were amplified from genomic DNA extracted from blood samples and analyzed by direct sequencing. In one family with apparently dominant inheritance of RP, linkage analysis identified an interval on the X chromosome containing RPGR, and mutation screening revealed a pathogenic variant in this gene. Patients of this family were examined clinically and by X-inactivation studies. RESULTS: This study included 141 RP families with possible X-chromosomal inheritance. In total, we identified 46 families with pathogenic sequence alterations in RPGR and RP2, of which 17 mutations have not been described previously. Two of the novel mutations represent the most 3'-terminal pathogenic sequence variants in RPGR and RP2 reported to date. In exon ORF15 of RPGR, we found eight novel and 14 known mutations. All lead to a disruption of open reading frame. Of the families with suggested X-chromosomal inheritance, 35% showed mutations in ORF15. In addition, we found five novel mutations in other exons of RPGR and four in RP2. Deletions in ORF15 of RPGR were identified in three families in which female carriers showed variable manifestation of the phenotype. Furthermore, an ORF15 mutation was found in an RP patient who additionally carries a 6.4 kbp deletion downstream of the coding region of exon ORF15. We did not identify mutations in 39 sporadic male cases from Switzerland. CONCLUSIONS: RPGR mutations were confirmed to be the most frequent cause of RP in families with an X-chromosomal inheritance pattern. We propose a screening strategy to provide molecular diagnostics in these families.

IFT20 modulates ciliary PDGFRα signaling by regulating the stability of Cbl E3 ubiquitin ligases.

Primary cilia have pivotal roles as organizers of many different signaling pathways, including platelet-derived growth factor receptor α (PDGFRα) signaling, which, when aberrantly regulated, is associated with developmental disorders, tumorigenesis, and cancer. PDGFRα is up-regulated during ciliogenesis, and ciliary localization of the receptor is required for its appropriate ligand-mediated activation by PDGF-AA. However, the mechanisms regulating sorting of PDGFRα and feedback inhibition of PDGFRα signaling at the cilium are unknown. Here, we provide evidence that intraflagellar transport protein 20 (IFT20) interacts with E3 ubiquitin ligases c-Cbl and Cbl-b and is required for Cbl-mediated ubiquitination and internalization of PDGFRα for feedback inhibition of receptor signaling. In wild-type cells treated with PDGF-AA, c-Cbl becomes enriched in the cilium, and the receptor is subsequently ubiquitinated and internalized. In contrast, in IFT20-depleted cells, PDGFRα localizes aberrantly to the plasma membrane and is overactivated after ligand stimulation because of destabilization and degradation of c-Cbl and Cbl-b.

The -11377 C>G promoter variant of the adiponectin gene, prevalence of coronary atherosclerosis, and incidence of vascular events in men.

No prospective data demonstrating an association between the -11377 C > G adiponectin gene promoter variant and cardiovascular risk are available. We therefore prospectively evaluated the cardiovascular risk associated with adiponectin gene single nucleotide polymorphisms (SNPs) including SNP -11377 in a consecutive series of men undergoing coronary angiography. We recorded vascular events over four years in 402 men undergoing coronary angiography for the evaluation of coronary artery disease. No significant associations of SNPs +276 G > T and +45 T > G with serum adiponectin, with significant coronary stenoses >50%, or with vascular events were observed. However, for SNP -11377 C > G, serum adiponectin levels significantly decreased (p(trend) = 0.003), and the prevalence of significant coronary stenoses significantly increased from the CC over the GC to the GG genotype (p(trend) = 0.004). Prospectively, the risk of vascular events significantly increased from the CC over the CG to the GG genotype of this SNP (adjusted hazard ratios 1.555 [0.957 - 2.525] and 2.309 [1.067 - 4.998], respectively; p(trend) = 0.014). The -11377 C > G adiponectin gene promoter variant is i) associated with decreased serum adiponectin levels, ii) correlated with the presence of coronary atherosclerosis and iii) significantly predictive of vascular events among men undergoing coronary angiography.

Relationship between the adipose-tissue hormone resistin and coronary artery disease.

BACKGROUND: Data on the cardiovascular risk associated with the adipose-tissue-related hormone resistin are scarce. METHODS: We measured serum resistin and established vascular risk factors in 547 consecutive patients (age 63+/-10 years) undergoing coronary angiography for the evaluation of stable coronary artery disease. Prospectively, we recorded major coronary events and cumulative vascular events over 4 years. RESULTS: 60% of our patients had significant coronary stenoses with a lumen narrowing > or =50%. Serum resistin was moderately but significantly correlated with age (r=0.139; p=0.001), high-sensitivity C-reactive protein (hsCRP; r=0.228; p<0.001) and decreasing renal function (r=0.240; p<0.001). However, there was no significant difference of serum resistin between patients with CAD and those in whom angiography did not show CAD (4.5 [3.1-5.8] vs. 4.3 [3.4-5.3] ng/ml; p=0.545) and between patients with > or =50% coronary narrowings and those without such lesions (4.5 [3.2-5.9] vs. 4.3 [3.1-5.5] ng/ml; p=0.265). Prospectively, Cox regression analyses neither indicated an association between serum resistin and major coronary events nor between serum resistin and cumulative vascular events. CONCLUSIONS: Among coronary patients serum resistin is significantly correlated with hsCRP, age and decreasing renal function but resistin is neither associated with the presence of significant coronary stenoses nor with the incidence of future vascular events.

Adult Treatment Panel III 2001 but not International Diabetes Federation 2005 criteria of the metabolic syndrome predict clinical cardiovascular events in subjects who underwent coronary angiography.

OBJECTIVE: The International Diabetes Federation (IDF) has recently established a worldwide consensus definition of the metabolic syndrome. No prospective data are available on the cardiovascular risk associated with this new metabolic syndrome definition. RESEARCH DESIGN AND METHODS: In a prospective study of 750 coronary patients, we recorded vascular events over 4 years. RESULTS: From our patients, 37.3% (n = 280) had the metabolic syndrome according to the Adult Treatment Panel III (ATPIII) definition and 45.5% (n = 341) according to the IDF definition. The metabolic syndrome as defined by the ATPIII criteria significantly predicted vascular events (adjusted hazard ratio 1.745 [95% CI 1.255-2.427]; P = 0.001), but the metabolic syndrome as defined by IDF criteria did not (1.189 [0.859-1.646]; P = 0.297). Accordingly, event-free survival was significantly lower among patients who fulfilled the ATPIII but not the IDF criteria than among those who met the IDF but not the ATPIII criteria (P = 0.012). The metabolic syndrome as defined by ATPIII criteria remained significantly predictive of vascular events after adjustment for type 2 diabetes but not after additional adjustment for the metabolic syndrome components high triglycerides and low HDL cholesterol. These lipid traits in turn proved significantly predictive of vascular events even after adjustment for the metabolic syndrome. CONCLUSIONS: The ATPIII definition of the metabolic syndrome confers a significantly higher risk of vascular events than the IDF definition. However, among angiographied coronary patients, even the ATPIII definition of the metabolic syndrome does not provide prognostic information beyond its dyslipidemic features.

Analgesia via blockade of NGF/TrkA signaling does not influence fracture healing in mice.

Abatement of fracture-related pain is important in patient welfare. However, the frequently used non-steroidal anti-inflammatory drugs are considered to impair fracture healing through blockade of cyclooxygenase-2. An alternative for fracture-related pain treatment may be blockade of nerve growth factor (NGF)/neurotrophic tyrosine kinase receptor type 1 (TrkA) signaling. Because the effect of blocking this signal-pathway on bone healing has not been extensively investigated, we addressed this issue by applying neutralizing antibodies that target NGF and TrkA, respectively, in a mouse fracture model. Mice with a knock-in for human TrkA underwent femur osteotomy and were randomly allocated to phosphate-buffered-saline, anti-NGF-antibody, or anti-TrkA-antibody treatment. The analgesic effect of the antibodies was determined from the activity and the ground reaction force of the operated limb. The effect of antibody administration on fracture healing was assessed by histomorphometry, micro-computed tomography, and biomechanics. NGF/TrkA-signaling blockade had no negative effect on fracture healing as callus formation and maturation were not altered. Mice treated with anti-TrkA antibody displayed significantly greater activity on post-operative day 2 compared to PBS treatment indicating effective analgesia. Our data indicate, that blockade of NGF/TrkA signaling via specific neutralizing antibodies for pain reduction during fracture healing does not influence fracture healing.

Neuritogenic surfaces using natural product analogs.

Neuritogenic surfaces are generated by a simple dip-coating procedure, as glass slides are coated with a neurotrophin-like small organic molecule in the presence of a collagen matrix. The surfaces retain their biological activity for multiple cycles and the protocol is suitable for various substrates and coating conditions.

A gene therapeutic approach to correct splice defects with modified U1 and U6 snRNPs.

Splicing is an essential cellular process to generate mature transcripts from pre-mRNA. It requires the splice factor U1 small nuclear ribonucleoprotein (U1), which promotes exon recognition by base-pairing interaction with the splice donor site (SD). After U1 dissociation, exon recognition is maintained by U6 small nuclear ribonucleoproteins (U6). It has been shown that SD mutations lower the binding affinity of U1 and cause splice defects in about 10% of patients with monogenetic diseases. U1 isoforms specifically designed to bind the mutated SD with increased affinity can correct these splice defects. We investigated the applicability of this gene therapeutic approach for different mutated SD positions. A minigene-based splicing assay was established to study a typical SD derived from the gene BBS1. We found that mutations at seven SD positions caused splice defects. In four cases, mutation-adapted U1 isoforms completely corrected these splice defects. Partial correction was found for splice defects induced by the mutation at SD position +5. The limited therapeutic efficacy at this position was alleviated by applying a combined treatment with mutation-adapted U1 and U6. The sequence complementarity between U6 and three SD positions (+4, +5,and +6) was relevant for the outcome of the therapy. Between 30 and 100% of the normal transcripts can be restored. The treatment significantly decreased both exon skipping and intron retention. Massive missplicing of off-target transcripts was not detected. Our study helps to assess the therapeutic efficacy of mutation-adapted U snRNAs in gene therapy and illustrates their strong potential to correct splice defects, which cause many different inherited conditions.

Catalytic enantioselective total synthesis of (+)-torrubiellone C.

Silyl-protected (R)-methyl 2-(hydroxymethyl)butanoate was obtained by an enantioselective Ir-catalyzed hydrogenation in high yield and selectivity. Elaboration of this building block via Takai and Stille reactions gave a protected hydroxy polyene chain, which was coupled to a 5-hydroxyphenyl-4-hydroxy-2-pyridone derivative by a modified Horner-Wadsworth-Emmons reaction. Deprotection gave synthetic (+)-torrubiellone C, which led to the assignment of the configuration of the natural product as (R).