Maintenance Of Cellular Integrity Research Articles

YdbH and YnbE form an intermembrane bridge to maintain lipid homeostasis in the outer membrane of Escherichia coli

The outer membrane (OM) of didermic gram-negative bacteria is essential for growth, maintenance of cellular integrity, and innate resistance to many antimicrobials. Its asymmetric lipid distribution, with phospholipids in the inner leaflet and lipopolysaccharides (LPS) in the outer leaflet, is required for these functions. Lpt proteins form a transenvelope bridge that transports newly synthesized LPS from the inner membrane (IM) to OM, but how the bulk of phospholipids are transported between these membranes is poorly understood. Recently, three members of the AsmA-like protein family, TamB, YhdP, and YdbH, were shown to be functionally redundant and were proposed to transport phospholipids between IM and OM in Escherichia coli. These proteins belong to the repeating β-groove superfamily, which includes eukaryotic lipid-transfer proteins that mediate phospholipid transport between organelles at contact sites. Here, we show that the IM-anchored YdbH protein interacts with the OM lipoprotein YnbE to form a functional protein bridge between the IM and OM in E. coli. Based on AlphaFold-Multimer predictions, genetic data, and in vivo site-directed cross-linking, we propose that YnbE interacts with YdbH through β-strand augmentation to extend the continuous hydrophobic β-groove of YdbH that is thought to shield acyl chains of phospholipids as they travel through the aqueous intermembrane periplasmic compartment. Our data also suggest that the periplasmic protein YdbL prevents extensive amyloid-like multimerization of YnbE in cells. We, therefore, propose that YdbL has a chaperone-like function that prevents uncontrolled runaway multimerization of YnbE to ensure the proper formation of the YdbH-YnbE intermembrane bridge.

Determining chromatin architecture with Micro Capture-C.

Micro Capture-C (MCC) is a chromatin conformation capture (3C) method for visualizing reproducible three-dimensional contacts of specified regions of the genome at base pair resolution. These methods are an established family of techniques that use proximity ligation to assay the topology of chromatin. MCC can generate data at substantially higher resolution than previous techniques through multiple refinements of the 3C method. Using a sequence agnostic nuclease, the maintenance of cellular integrity and full sequencing of the ligation junctions, MCC achieves subnucleosomal levels of resolution, which can be used to reveal transcription factor binding sites analogous to DNAse I footprinting. Gene dense regions, close-range enhancer-promoter contacts, individual enhancers within super-enhancers and multiple other types of loci or regulatory regions that were previously challenging to assay with conventional 3C techniques, are readily observed using MCC. MCC requires training in common molecular biology techniques and bioinformatics to perform the experiment and analyze the data. The protocol can be expected to be completed in a 3 week timeframe for experienced molecular biologists.

The single Marchantia polymorpha FERONIA homolog reveals an ancestral role in regulating cellular expansion and integrity.

Plant cells are surrounded by a cell wall, a rigid structure that is not only important for cell and organ shape, but is also crucial for intercellular communication and interactions with the environment. In the flowering plant Arabidopsis thaliana, the 17 members of the Catharanthus roseus RLK1-like (CrRLK1L) receptor kinase family are involved in a multitude of physiological and developmental processes, making it difficult to assess their primary or ancestral function. To reduce genetic complexity, we characterized the single CrRLK1L gene of Marchantia polymorpha, MpFERONIA (MpFER). Plants with reduced MpFER levels show defects in vegetative development, i.e. rhizoid formation and cell expansion, and have reduced male fertility. In contrast, cell integrity and morphogenesis of the gametophyte are severely affected in Mpfer null mutants and MpFER overexpression lines. Thus, we conclude that the CrRLK1L gene family originated from a single gene with an ancestral function in cell expansion and the maintenance of cellular integrity. During land plant evolution, this ancestral gene diversified to fulfill a multitude of specialized physiological and developmental roles in the formation of both gametophytic and sporophytic structures essential to the life cycle of flowering plants.

Molecular adaptations to heat stress in the thermophilic ant genus Cataglyphis.

Over the last decade, increasing attention has been paid to the molecular adaptations used by organisms to cope with thermal stress. However, to date, few studies have focused on thermophilic species living in hot, arid climates. In this study, we explored molecular adaptations to heat stress in the thermophilic ant genus Cataglyphis, one of the world's most thermotolerant animal taxa. We compared heat tolerance and gene expression patterns across six Cataglyphis species from distinct phylogenetic groups that live in different habitats and experience different thermal regimes. We found that all six species had high heat tolerance levels with critical thermal maxima (CTmax ) ranging from 43℃ to 45℃ and a median lethal temperature (LT50) ranging from 44.5℃ to 46.8℃. Transcriptome analyses revealed that, although the number of differentially expressed genes varied widely for the six species (from 54 to 1118), many were also shared. Functional annotation of the differentially expressed and co-expressed genes showed that the biological pathways involved in heat-shock responses were similar among species and were associated with four major processes: the regulation of transcriptional machinery and DNA metabolism; the preservation of proteome stability; the elimination of toxic residues; and the maintenance of cellular integrity. Overall, our results suggest that molecular responses to heat stress have been evolutionarily conserved in the ant genus Cataglyphis and that their diversity may help workers withstand temperatures close to their physiological limits.

Oxidative Chemical Stressors Alter the Physiological State of the Nasal Olfactory Mucosa of Atlantic Salmon.

The olfactory organs of fish have vital functions for chemosensory and defence. Though there have been some ground-breaking discoveries of their involvement in immunity against pathogens in recent years, little is known about how they respond to non-infectious agents, such as exogenous oxidants, which fish encounter regularly. To this end, we employed Atlantic salmon (Salmo salar) as a model to study the molecular responses at the nasal olfactory mucosa of a teleost fish when challenged with oxidants. Microarray analysis was employed to unravel the transcriptional changes at the nasal olfactory mucosa following two types of in vivo exposure to peracetic acid (PAA), a highly potent oxidative agent commonly used in aquaculture: Trial 1: periodic and low dose (1 ppm, every 3 days over 45 days) to simulate a routine disinfection; and Trial 2: less frequent and high dose (10 ppm for 30 min, every 15 days, 3 times) to mimic a bath treatment. Furthermore, leukocytes from the olfactory organ were isolated and exposed to PAA, as well as to hydrogen peroxide (H2O2) and acetic acid (AA)—the two other components of PAA trade products—to perform targeted cellular and molecular response profiling. In the first trial, microarrays identified 32 differentially expressed genes (DEG) after a 45-day oxidant exposure. Erythrocyte-specific genes were overly represented and substantially upregulated following exogenous oxidant exposure. In Trial 2, in which a higher dose was administered, 62 DEGs were identified, over 80% of which were significantly upregulated after exposure. Genes involved in immune response, redox balance and stress, maintenance of cellular integrity and extracellular matrix were markedly affected by the oxidant. All chemical stimuli (i.e., PAA, H2O2, AA) significantly affected the proliferation of nasal leukocytes, with indications of recovery observed in PAA- and H2O2-exposed cells. The migration of nasal leukocytes was promoted by H2O2, but not much by PAA and AA. The three chemical oxidative stressors triggered oxidative stress in nasal leukocytes as indicated by an increase in the intracellular reactive oxygen species level. This resulted in the mobilisation of antioxidant defences in the nasal leukocytes as shown by the upregulation of crucial genes for this response network. Though qPCR revealed changes in the expression of selected cytokines and heat shock protein genes following in vitro challenge, the responses were stochastic. The results from the study advance our understanding of the role that the nasal olfactory mucosa plays in host defence, particularly towards oxidative chemical stressors.

Genotoxic property of poly herbal formulation of annona squomosa, zingiber officinalis and triticum aestivum plant extracts by in vitro chromosomal aberration test

The present study was aimed to evaluate the genotoxic potential of polyherbal formulations by chromosomal aberration test. Cancer being the second most cause of death among all ailments even after the improvised medications needs alternative sources of treatment. Herbal sources were always among the one as prime treatment sources. Polyherbal formulations were taking the lead in medications because of their broad spectrum of activity and synergic effects. Annona squamosa, Zingiber Officinalis, and Triticum Aestivum formulation with 1:2:3 ratio has shown significant results in the definitive and confirmatory chromosome aberration assays. Indicated the test article PF3 did not induce a statistically significant increase in the percentage of cells with aberrations both in the presence and absence of metabolic activation. PF3 was found non-clostagenic at a maximum dose of 15 µg/ml in the CHO cell line. Inhibition of chromosomal aberration, DNA fragmentation, and maintenance of cellular integrity may prevent the genotoxic effect. Further optimization and in vivo authenticated studies need to be proven.

Дія L-глутамінової кислоти та піридоксину на імунологічні й гематологічні показники за дії епінефрин-індукованого стресу в щурів

Відомо, що глутамінова кислота (L-Glu) є найпоширенішою й універсальною амінокислотою в організмі. Майже в кожній клітині L-Glu може бути використана як субстрат для синтезу нуклеотидів, NADPH, антиоксидантів та багатьох інших біосинтетичних шляхів, що беруть участь у підтримці клітинної цілісності. Цитопротекторні й антиоксидантні властивості L-Glu можуть бути надзвичайно важливими в умовах окисного стресу. Пошук речовин, які б сприяли більш швидкій адаптації організму в умовах оксидаційного стресу, є особливо актуальним. Мета роботи – дослідити дію L-Glu як окремо, так і в поєднанні з піридоксином (L-Glu+Pyr) за дії епінефриніндукованого стресу в щурів. У наших дослідженнях для пом’якшення дії оксидаційного стресу ми досліджували вплив вищезгаданих речовин на показники Т- і В-клітинного імунітету, загальну кількість еритроцитів і лейкоцитів та фагоцитарну активність нейтрофілів.У результаті дослідження встановлено, що після застосування епінефрину та додаткового введення L-Glu і L-Glu+Pyr змінюється рецепторний апарат Т-лімфоцитів. Виявлено, що внутрішньоочеревинне введення епінефрину першій дослідній групі тварин, що зазнавала дії стресу, без додаткового застосування L-Glu й L-Glu+Pyr зумовило підвищення індексу співвідношення Т-хелперів до цитотоксичних Т-лімфоцитів, відносний уміст яких був вірогідно вищим (р0,05) відносно контролю. Відзначено зниження кількості загальних Т-лімфоцитів і з нульовою (0) та середньою (6–10) щільністю рецепторів (р<0,05), кількості Т-супресорів (р0,05) у тварин першої дослідної групи, порівняно з контрольною групою тварин. Додаткове введення L-Glu і L-Glu+Pyr впливало на Т-клітинну ланку імунітету, а саме на кількість Т-загальних лімфоцитів за допомогою підвищення захисних сил організму, про що може свідчити відсутність змін, порівняно з контролем.

Prolonged erythrocyte auto-incubation as an alternative model for oxidant generation system

This study investigated the effects of incubation period and melatonin treatment on red blood cell (RBC) metabolism in an auto-incubation model of H2O2-induced oxidative stress. The study was carried out on three healthy adult donors by incubating RBCs in their own plasma at 37 °C, or under the influence of 1 mM H2O2 with and without 100 μM melatonin at different times (0, 1, 3 and 6 h). We assessed incubation period, treatment, as well as any interaction effects between these predictors on erythrocyte osmoregulation, hemolytic rate, oxidative stress markers, and adenylate nucleotide levels. We did not find any relevant effects of both incubation period and treatments on osmotic, antioxidant and adenylate parameters. On the other hand, hemolysis degree and biomolecule oxidation levels in the plasma increased over time, 3-fold and about 25%, respectively, regardless any treatment influence. H2O2 treatment more than doubled protein carbonyl groups, regardless time in plasma, and in a time-depending way in erythrocyte membrane extract, effects that were neutralized by melatonin treatment. Through multivariate analyses, we could expand the understanding of energy and redox metabolisms in the maintenance of cellular integrity and metabolic homeostasis. Another interesting observation was the 65–75% contribution of the oxidative lesion markers on hemolysis. Hence, these findings suggested a new and more intuitive RBC suspension model and reinforced the beneficial use of melatonin in human disorders.

MYOFIBRILLAR AND DISTAL MYOPATHIES: P.253Severe intestinal pseudo-obstruction in a p.R405W desmin knock-in model: a new phenotype lead to light smooth muscle involvement in myofibrillar myopathies

The intermediate filament desmin, specifically expressed in striated and smooth muscle cells, forms a filament network which provides maintenance of cellular integrity, resistance to mechanical stress, force transmission and mechanochemical signaling. Abnormal expression or lack of desmin leads to a progressive disruption of the contractile machinery, which can be observed in the muscles from patients affected by myofibrillar myopathies (MFM) due to mutations of the desmin gene DES (DES-MFM). To clarify the pathophysiology of DES-MFM, we generated a mouse KI model expressing the R405W DES mutation, homologous to human R406W. This mutation is associated with a severe and relatively early clinical phenotype in patients, which develop muscular weakness, cardiopathy and respiratory failure from the third decade of life. Molecular studies showed that p.Arg406Trp desmin has a reduced ability to support longitudinal annealing as well as radial compaction, two essential steps required for the formation of the desmin network. Heterogygous DesWT/R405W as well as homozygous DesR405W/R405W KI mice showed abnormal accumulation of desmin at the subsarcolemmal membrane in striated muscles. Homozygous animals died early (at 3.4 ± 1.2 months) and developed severe dilatation of the intestinal tract associated with food stasis in the lumen around 3 months. Echographic and histological studies showed a thickening of the colon and desmin aggregates in all muscle segments of the digestive tract. Functional studies revealed reduced spontaneous contraction and strength generation of the homozygous duodenum, suggesting an alteration of the mechanical properties of smooth muscle cells. Intestinal malapsorption and pseudo-obstruction have been reported in very rare DES-MFM patients. Our model brings to light the importance of desmin for intestinal smooth muscles, and suggests that smooth muscle involvement may have been underestimated in patients suffering from MFMs.

Potential Contributions of Antioxidants to Cancer Therapy: Immunomodulation and Radiosensitization.

Antioxidants play important roles in the maintenance of cellular integrity and thus are critical in maintaining the homeostasis of the host immune system. A balance between the levels of pro-oxidants and antioxidants defines the cellular fate of genomic integrity via maintaining the redox status of the cells. An aberration in this balance modulates host immunity that affects normal cellular signaling pathways resulting in uncontrolled proliferation of cells leading to neocarcinogenesis. For decades, there have been scientific debates on the use of antioxidants for the treatment of human cancers. This review is focused on current updates on the implications of antioxidant use as adjuncts in cancer therapy with an emphasis on immunomodulation and radiosensitization.

Behaviors of Microcystis aeruginosa cells during floc storage in drinking water treatment process.

This is the first study to systematically investigate the different behaviors of Microcystis aeruginosa in the sludges formed by AlCl3, FeCl3, and polymeric aluminium ferric chloride (PAFC) coagulants during storage. Results show that the viability of Microcystis aeruginosa in PAFC sludge was stronger than that of cells in either AlCl3 or FeCl3 sludge after the same storage time, while the cells’ viability in the latter two systems stayed at almost the same level. In AlCl3 and FeCl3 sludges high concentrations of Al and Fe were toxic to Microcystis aeruginosa, whereas in PAFC sludge low levels of Al showed little toxic effect on Microcystis aeruginosa growth and moderate amounts of Fe were beneficial to growth. The lysis of Microcystis aeruginosa in AlCl3 sludge was more serious than that in PAFC sludge, for the same storage time. Although the cell viability in FeCl3 sludge was low (similar to AlCl3 sludge), the Microcystis aeruginosa cells remained basically intact after 10 d storage (similar to PAFC sludge). The maintenance of cellular integrity in FeCl3 sludge might be due to the large floc size and high density, which had a protective effect for Microcystis aeruginosa.

Outer membrane lipoprotein VacJ is required for the membrane integrity, serum resistance and biofilm formation of Actinobacillus pleuropneumoniae

The outer membrane proteins of Actinobacillus pleuropneumoniae are mediators of infection, acting as targets for the host’s defense system. The outer membrane lipoprotein VacJ is involved in serum resistance and intercellular spreading in several pathogenic bacteria. To investigate the role of VacJ in the pathogenicity of Actinobacillus pleuropneumoniae, the vacJ gene-deletion mutant MD12 ΔvacJ was constructed. The increased susceptibility to KCl, SDS plus EDTA, and several antibiotics in the MD12ΔvacJ mutant suggested that the stability of the outer membrane was impaired as a result of the mutation in the vacJ gene. The increased NPN fluorescence and significant cellular morphological variation in the MD12ΔvacJ mutant further demonstrated the crucial role of the VacJ lipoprotein in maintaining the outer membrane integrity of A. pleuropneumoniae. In addition, the MD12ΔvacJ mutant exhibited decreased survival from the serum and complement killing compared to the wild-type strain. Interestingly, the MD12ΔvacJ mutant showed reduced biofilm formation compared to the wild-type strain. To our knowledge, this is the first description of the VacJ lipoprotein contributing to bacterial biofilm formation. The data presented in this study illustrate the important role of the VacJ lipoprotein in the maintenance of cellular integrity, serum resistance, and biofilm formation in A. pleuropneumoniae.

Excess iron alters the fatty acid composition of chloroplast membrane and decreases the photosynthesis rate: a study in hydroponic pea seedlings

As an essential micronutrient, iron (Fe) is directly involved in several fundamental processes in the photosynthetic cells. However, it is not clear if photosynthetic traits affected by high ferrous level are associated with changes in fatty acid composition in chloroplast membranes. To accomplish this, the effects of excess Fe2+ on the fatty acid composition and the fluidity properties of the chloroplast membrane, photosynthesis rate and the chlorophyll fluorescence were investigated in pea (Pisum sativum L.) seedlings grown hydroponically in nutrient solutions with 100, 200, 400 and 600 µM Fe2+ supplied as FeSO4. Increased fluidity of the chloroplast membranes was found under higher Fe2+ treatments, and this might be attributed to the increase in relative content of unsaturated fatty acids (USFA). Excess Fe2+ decreased the chlorophyll content and the electron transport rate, deactivated reaction center of photosystem II, and declined plant net photosynthetic rate. Finally, the reduced plant dry weight was observed. The results indicate that the effects of excess Fe on photosynthesis and fluidity of chloroplast membrane depend on the stress strength and duration, and the increased fluidity of chloroplast membrane may be critical in maintenance of cellular integrity under excess but not lethiferous Fe2+ treatment.

Cellular response to the genotoxic insult: the question of threshold for genotoxic carcinogens

Maintenance of cellular integrity is crucial for its physiological function, which is constantly threatened by DNA damage arising from numerous intrinsic and environmental sources.

Differential expression of HO-1 and CYP1A2 during up-regulation of ERK in stressed fish hepatocytes.

Induction of heme oxygenase-1 (HO-1) and extracellular signal-regulated kinase (ERK) is a crucial step in the cellular response to oxidative stress. Altered expression of such proteins in response to stress conditions is a key factor for the maintenance of cellular integrity and survival. Hypoxia-inducible factor-1 (HIF-1) and cytochrome P450 1A (CYP1A) are critical indicators of environmental exposure to hypoxia. The current study was aimed to analyse the expression pattern of HO-1, p-ERK, HIF-1α and CYP1A2 in hepatocytes of Mugil cephalus inhabiting Kovalam (unpolluted site) and Ennore (polluted site) estuaries. The impact of stress on hepatocytes was assessed by measuring the level of lipid hydroperoxides (LHP) and reduced glutathione (GSH) in hepatocytes of M. cephalus inhabiting these estuaries. The expression of HO-1, p-ERK, HIF-1α and CYP1A2 was analysed by ELISA and immunoblot analysis, respectively. There was significant decrease of GSH (19%) and CYP1A2 (34%) along with significant increase of LHP (31%), HO-1 (96%), p-ERK (p < 0.01) and HIF-1α (41%) in hepatocytes of M. cephalus inhabiting Ennore estuary than Kovalam estuary. The present study shows that increased synthesis of HO-1 mainly regulated by p-ERK and HIF-1α may significantly contribute to the environmental adaptation processes of grey mullet, by protecting the cells from oxidative stress and stress-induced degenerative changes.

Is Selective Antegrade Cerebral Perfusion Superior to Retrograde Cerebral Perfusion for Brain Protection During Deep Hypothermic Circulatory Arrest? Metabolic Evidence From Microdialysis

This study aimed to investigate whether selective antegrade cerebral perfusion or retrograde cerebral perfusion is a better technique for brain protection in deep hypothermic circulatory arrest by obtaining metabolic evidence from microdialysis. Randomized, animal study. Assisted circulation laboratory. Eighteen piglets of either sex (9.8 ± 3.1 kg). Animals were randomly assigned to 40 minutes of circulatory arrest at 18°C without cerebral perfusion (deep hypothermic circulatory arrest group, n = 6) or with selective antegrade cerebral perfusion (selective antegrade cerebral perfusion group, n = 6) or retrograde cerebral perfusion (retrograde cerebral perfusion group, n = 6). Reperfusion was continued for 3 hours. Microdialysis (glucose, lactate, pyruvate, and glycerol) variables in the cortex dialysate were measured every 30 minutes. Intracerebral pressure and serum S-100 levels were also monitored. After 3 hours of reperfusion, cortical tissue was harvested for terminal deoxynucleotidyl transferase dUTP nick-end labeling staining. After 40 minutes of circulatory arrest, the deep hypothermic circulatory arrest group presented marked elevations of intracerebral pressure, and serum S-100 levels were higher in the deep hypothermic circulatory arrest group than in the other two groups (p < 0.001, respectively). The selective antegrade cerebral perfusion group exhibited higher glucose, lower lactate, and lower glycerol levels and a lower lactate-to-pyruvate ratio in comparison to the deep hypothermic circulatory arrest group (p < 0.05, respectively); the retrograde cerebral perfusion group had lower lactate and glycerol levels and a lower lactate-to-pyruvate ratio (p < 0.05, respectively) but similar glucose levels compared to deep hypothermic circulatory arrest alone. Furthermore, selective antegrade cerebral perfusion provided better preservation of energy and cell integrity than retrograde cerebral perfusion with higher glucose and lower glycerol levels (p < 0.05, respectively). After 3 hours of reperfusion, fewer apoptotic neurons were found in selective antegrade cerebral perfusion animals than in the other two groups (p < 0.05, respectively). Both selective antegrade cerebral perfusion and retrograde cerebral perfusion were superior to deep hypothermic circulatory arrest alone during circulatory arrest. Retrograde cerebral perfusion was a moderate technique that had similar advantages with regard to less cerebral edema, better clearance of metabolic waste, and lower levels of biomarkers of injury than selective antegrade cerebral perfusion, but its capacity for energy preservation, maintenance of cellular integrity, and protection against apoptosis was lower than that of selective antegrade cerebral perfusion.

MARCH5-mediated quality control on acetylated Mfn1 facilitates mitochondrial homeostasis and cell survival.

Mitochondrial dynamics and quality control have a central role in the maintenance of cellular integrity. Mitochondrial ubiquitin ligase membrane-associated RING-CH (MARCH5) regulates mitochondrial dynamics. Here, we show that mitochondrial adaptation to stress is driven by MARCH5-dependent quality control on acetylated Mfn1. Under mitochondrial stress conditions, levels of Mfn1 were elevated twofold and depletion of Mfn1 sensitized these cells to apoptotic death. Interestingly, overexpression of Mfn1 also promoted cell death in these cells, indicating that a fine tuning of Mfn1 levels is necessary for cell survival. MARCH5 binds Mfn1 and the MARCH5-dependent Mfn1 ubiquitylation was significantly elevated under mitochondrial stress conditions along with an increase in acetylated Mfn1. The acetylation-deficient K491R mutant of Mfn1 showed weak interaction with MARCH5 as well as reduced ubiquitylation. Neither was observed in the acetylation mimetic K491Q mutant. In addition, MARCH5-knockout mouse embryonic fibroblast and MARCH5H43W-expressing HeLa cells lacking ubiquitin ligase activity experienced rapid cell death upon mitochondrial stress. Taken together, a fine balance of Mfn1 levels is maintained by MARCH5-mediated quality control on acetylated Mfn1, which is crucial for cell survival under mitochondria stress conditions.

Recessive desmin-null muscular dystrophy with central nuclei and mitochondrial abnormalities

missense mutations. However, very few families with a recessive mode of inheritance have also been recognized [2]. Desmin immunostaining of normal skeletal muscle shows uniform sarcoplasmic and subsarcolemmal localization, while affected muscles display cytoplasmic aggregates of misfolded filaments and disruption of the myofibrillar apparatus rather than absence of protein [2], so that individuals with desmin mutations are frequently categorized within the group of disorders known as myofibrillar myopathies. We describe a family with no history of neuromuscular or cardiac disorders with two siblings affected by autosomal recessive desminopathy manifesting as a slowly progressive, predominantly proximal muscle fatigue and weakness. The proband, a 12 year old boy, was born at term and had normal gross motor milestones, but presented poor head control when crawling, lack of facial expression and congenital ptosis. From the age of 3 he showed difficulty rising from the floor, jumping, running and going upstairs. The weakness was slowly progressive over the years and he remains independently mobile. He tires easily and benefits from short breaks. On examination he presented with shoulder, grip and hip muscle weakness, symmetrical scapular winging, mild thoracic scoliosis and mild bilateral calf hypertrophy. Muscle MRI features are shown in Fig. 1a. He shows an unusual pattern of swallowing, turning his neck to ingest food, but he has a good appetite and is generally healthy. Forced vital capacity (FVC) was 45 % of the predicted value in sitting. CK levels were raised up to 1,000 IU/L, cardiac examinations were normal. His 11 year old sister displayed a slightly less pronounced weakness, contractures of long finger flexors and shoulders and hyperextensible elbows as well as similar tiredness and swallowing habit as her brother. She has a small appetite with a weight below the 3rd centile and also presents a history of asthma and rare chest infections. Her FVC was 40 % of the predicted value Desmin is a muscle-specific intermediate filament that provides maintenance of cellular integrity and force transmission [2]. DES gene mutations cause a spectrum of adult-onset disorders, ranging from myopathies with and without cardiac involvement to cardiomyopathy without skeletal muscle involvement [3]. Distal and proximal weakness involving upper and lower limbs muscles are observed in most patients [9]. Desminopathies are usually inherited in an autosomal dominant fashion, predominantly with

Left ventricular hypertrophy caused by a novel nonsense mutation in FHL1

Emery Dreifuss muscular dystrophy (EDMD) is a hereditary muscular disorder, characterized by contractures, progressive muscular wasting and cardiac involvement. The majority of EDMD patients harbor mutations in the lamin A/C (LMNA) and emerin (STA) genes. Emerging data implicate mutations in FHL1 (four and a half LIM protein 1) gene, located in chromosome Xq26, in EDMD pathogenesis. FHL1 is mainly expressed in striated and cardiac muscle, and plays an important role in sarcomeric protein synthesis, maintenance of cellular integrity, intracellular signaling and genetic transcription pathways. We report the identification of a novel nonsense mutation in FHL1 gene, associated with left ventricular hypertrophy and a family history of stroke and sudden cardiac death. The management implications of this diagnosis are also discussed.

Tet proteins: on track towards DNA demethylation?

Abstract Dynamic DNA methylation is a prerequisite for many developmental processes and maintenance of cellular integrity. In mammals however, mechanisms of active DNA demethylation have for long been elusive. The discovery of the ten-eleven translocation (Tet) family of enzymes that oxidize 5-methylcytosine (5mC) to 5-hydroxymethylcytosine (5hmC), 5-formylcytosine (5fC) or 5-carboxylcytosine (5caC) provided new means by which DNA methylation could actively be reversed. This review focuses on the possible mechanisms of DNA demethylation via Tet proteins and their metabolites 5hmC, 5fC and 5caC. Additionally, it discusses the roles of the three Tet protein family members Tet1, Tet2 and Tet3 as developmental regulators, probably in part independent of their enzymatic activity. By contrast, recent evidence suggests a function of 5hmC as an epigenetic mark on its own, going beyond the expectation of only acting as an intermediate in an active DNA demethylation pathway.