Mutations of the BRAF gene in human cancer

Cancers arise owing to the accumulation of mutations in critical genes that alter normal programmes of cell proliferation, differentiation and death. As the first stage of a systematic genome-wide screen for these genes, we have prioritized for analysis signalling pathways in which at least one gene is mutated in human cancer. The RAS RAF MEK ERK MAP kinase pathway mediates cellular responses to growth signals. RAS is mutated to an oncogenic form in about 15% of human cancer. The three RAF genes code for cytoplasmic serine/threonine kinases that are regulated by binding RAS. Here we report BRAF somatic missense mutations in 66% of malignant melanomas and at lower frequency in a wide range of human cancers. All mutations are within the kinase domain, with a single substitution (V599E) accounting for 80%. Mutated BRAF proteins have elevated kinase activity and are transforming in NIH3T3 cells. Furthermore, RAS function is not required for the growth of cancer cell lines with the V599E mutation. As BRAF is a serine/threonine kinase that is commonly activated by somatic point mutation in human cancer, it may provide new therapeutic opportunities in malignant melanoma.

2.2 Mb of contiguous nucleotide sequence from chromosome III of C. elegans

As part of our effort to sequence the 100-megabase (Mb) genome of the nematode Caenorhabditis elegans, we have completed the nucleotide sequence of a contiguous 2,181,032 base pairs in the central gene cluster of chromosome III. Analysis of the finished sequence has indicated an average density of about one gene per five kilobases; comparison with the public sequence databases reveals similarities to previously known genes for about one gene in three. In addition, the genomic sequence contains several intriguing features, including putative gene duplications and a variety of other repeats with potential evolutionary implications.

Correlation between the human fecal microbiota and depression

BACKGROUND

Depression is a chronic syndrome with a pathogenesis linked to various genetic, biological, and environmental factors. Several links between gut microbiota and depression have been established in animal models. In humans, however, few correlations have yet been demonstrated. The aim of our work was therefore to identify potential correlations between human fecal microbiota (as a proxy for gut microbiota) and depression.

METHODS

We analyzed fecal samples from 55 people, 37 patients, and 18 non-depressed controls. Our analyses were based on data generated by Illumina deep sequencing of 16S rRNA gene amplicons.

KEY RESULTS

We found several correlations between depression and fecal microbiota. The correlations, however, showed opposite directions even for closely related Operational Taxonomic Units (OTU's), but were still associated with certain higher order phylogroups. The order Bacteroidales showed an overrepresentation (p = 0.05), while the family Lachnospiraceae showed an underrepresentation (p = 0.02) of OTU's associated with depression. At low taxonomic levels, there was one clade consisting of five OTU's within the genus Oscillibacter, and one clade within Alistipes (consisting of four OTU's) that showed a significant association with depression (p = 0.03 and 0.01, respectively).

CONCLUSIONS & INFERENCES

The Oscillibacter type strain has valeric acid as its main metabolic end product, a homolog of neurotransmitter GABA, while Alistipes has previously been shown to be associated with induced stress in mice. In conclusion, the taxonomic correlations detected here may therefore correspond to mechanistic models.

Intention tremor, parkinsonism, and generalized brain atrophy in male carriers of fragile X

The authors report five elderly men with the fragile X premutation who had a progressive action tremor associated with executive function deficits and generalized brain atrophy. These individuals had elevated fragile X mental retardation 1 gene (FMR1) messenger RNA and normal or borderline levels of FMR1 protein. The authors propose that elevations of FMR1 messenger RNA may be causative for a neurodegenerative syndrome in a subgroup of elderly men with the FMR1 premutation.

Fringe is a glycosyltransferase that modifies Notch

Notch receptors function in highly conserved intercellular signalling pathways that direct cell-fate decisions, proliferation and apoptosis in metazoans. Fringe proteins can positively and negatively modulate the ability of Notch ligands to activate the Notch receptor. Here we establish the biochemical mechanism of Fringe action. Drosophila and mammalian Fringe proteins possess a fucose-specific beta1,3 N-acetylglucosaminyltransferase activity that initiates elongation of O-linked fucose residues attached to epidermal growth factor-like sequence repeats of Notch. We obtained biological evidence that Fringe-dependent elongation of O-linked fucose on Notch modulates Notch signalling by using co-culture assays in mammalian cells and by expression of an enzymatically inactive Fringe mutant in Drosophila. The post-translational modification of Notch by Fringe represents a striking example of modulation of a signalling event by differential receptor glycosylation and identifies a mechanism that is likely to be relevant to other signalling pathways.

Fringe modulates Notch-ligand interactions

The Notch family of transmembrane receptor proteins mediate developmental cell-fate decisions, and mutations in mammalian Notch genes have been implicated in leukaemia, breast cancer, stroke and dementia. During wing development in Drosophila, the Notch receptor is activated along the border between dorsal and ventral cells, leading to the specification of specialized cells that express Wingless (Wg) and organize wing growth and patterning. Three genes, fringe (fng), Serrate (Ser) and Delta (Dl), are involved in the cellular interactions leading to Notch activation. Ser and Dl encode transmembrane ligands for Notch, whereas fng encodes a pioneer protein. We have investigated the relationship between these genes by a combination of expression and coexpression studies in the Drosophila wing. We found that Ser and Dl maintain each other's expression by a positive feedback loop. fng is expressed specifically by dorsal cells and functions to position and restrict this feedback loop to the developing dorsal-ventral boundary. This is achieved by fng through a cell-autonomous mechanism that inhibits a cell's ability to respond to Serrate protein and potentiates its ability to respond to Delta protein.

The ROOT MERISTEMLESS1/CADMIUM SENSITIVE2 gene defines a glutathione-dependent pathway involved in initiation and maintenance of cell division during postembryonic root development

Activation of cell division in the root apical meristem after germination is essential for postembryonic root development. Arabidopsis plants homozygous for a mutation in the ROOT MERISTEMLESS1 (RML1) gene are unable to establish an active postembryonic meristem in the root apex. This mutation abolishes cell division in the root but not in the shoot. We report the molecular cloning of the RML1 gene, which encodes the first enzyme of glutathione (GSH) biosynthesis, gamma-glutamylcysteine synthetase, and which is allelic to CADMIUM SENSITIVE2. The phenotype of the rml1 mutant, which was also evident in the roots of wild-type Arabidopsis and tobacco treated with an inhibitor of GSH biosynthesis, could be relieved by applying GSH to rml1 seedlings. By using a synchronized tobacco cell suspension culture, we showed that the G(1)-to-S phase transition requires an adequate level of GSH. These observations suggest the existence of a GSH-dependent developmental pathway essential for initiation and maintenance of cell division during postembryonic root development.

The C. elegans genome sequencing project: a beginning

The long-term goal of this project is the elucidation of the complete sequence of the Caenorhabditis elegans genome. During the first year methods have been developed and a strategy implemented that is amenable to large-scale sequencing. The three cosmids sequenced in this initial phase are surprisingly rich in genes, many of which have mammalian homologues.

A comparison of the visual analogue scale and modified Borg scale for the measurement of dyspnoea during exercise

1. The intensity of breathlessness during exercise was measured in ten normal subjects using a visual analogue scale (VAS) and a Borg scale to compare the use of the scales and their repeatability, both within the duration of a period of exercise and between tests. For each scale, subjects performed two exercise tests separated by a period of 2-6 weeks. Each exercise test consisted of two cycles of progressively increasing and decreasing workload. 2. All subjects felt confidently able to use both scales to quantify their feelings of breathlessness exclusively of other sensation. Equal preference was expressed for use of a particular scale. 3. With both scales there was a large intersubject variation in the relationship between dyspnoea score and minute ventilation (VE) (P less than 0.01), and in the range of the scale used. 4. There was a good correlation between the VAS and Borg scores at each level of VE (r2 = 0.71), but the VAS score was used over a wider range than the Borg score. 5. The relationship between VE and the dyspnoea score measured by the two techniques was predominantly linear. The mean r2 for VAS score/VE was 0.68 (SD 0.19) and for Borg score/VE the mean r2 was 0.75 (SD 0.13). 6. The relationships VAS score/VE and Borg score/VE were unaffected by the direction in which the workload was varied (P greater than 0.05). 7. VE, measured at each work rate, did not differ between the two cycles (P greater than 0.05) or between the 2 days (P greater than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Generation and analysis of 280,000 human expressed sequence tags

We report the generation of 319,311 single-pass sequencing reactions (known as expressed sequence tags, or ESTs) obtained from the 5' and 3' ends of 194,031 human cDNA clones. Our goal has been to obtain tag sequences from many different genes and to deposit these in the publicly accessible Data Base for Expressed Sequence Tags. Highly efficient automatic screening of the data allows deposition of the annotated sequences without delay. Sequences have been generated from 26 oligo(dT) primed directionally cloned libraries, of which 18 were normalized. The libraries were constructed using mRNA isolated from 17 different tissues representing three developmental states. Comparisons of a subset of our data with nonredundant human mRNA and protein data bases show that the ESTs represent many known sequences and contain many that are novel. Analysis of protein families using Hidden Markov Models confirms this observation and supports the contention that although normalization reduces significantly the relative abundance of redundant cDNA clones, it does not result in the complete removal of members of gene families.

Nuclear export of the stress-activated protein kinase p38 mediated by its substrate MAPKAP kinase-2

BACKGROUND

Mitogen-activated protein (MAP) kinases (or extracellular signal regulated kinases; Erks) and stress-activated protein (SAP) kinases mediate cellular responses to a wide variety of signals. In the Erk MAP kinase pathway, activation of MAP kinases takes place in the cytoplasm and the activated enzyme moves to the nucleus. This translocation to the nucleus is essential to MAP kinase signalling because it enables the kinase to phosphorylate transcription factors. Whether components of the pathway mediated by the SAP kinase p38 change their cellular location on activation is not clear; we have therefore studied the cellular localisation of components of this pathway before and after stimulation.

RESULTS

The p38 SAP kinase substrate MAP-kinase-activated protein kinase-2 (MAPKAP kinase-2) contains a putative nuclear localisation signal which we show is functional and required for activation by a variety of stimuli. Following phosphorylation of MAPKAP kinase-2, nuclear p38 was exported to the cytoplasm in a complex with MAPKAP kinase-2. Export of MAPKAP kinase-2 required phosphorylation by p38 but did not appear to require the kinase activity of MAPKAP kinase-2. The p38 activators MKK3 and MKK6 were present in both the nucleus and the cytoplasm, consistent with a role in activating p38 in the nucleus.

CONCLUSIONS

In the p38 SAP kinase pathway, MAPKAP kinase-2 serves both as an effector of p38 by phosphorylating substrates and as a determinant of cellular localisation of p38. Nuclear export of p38 and MAPKAP kinase-2 may permit them to phosphorylate substrates in the cytoplasm.

Measurement of Pseudomonas aeruginosa phenazine pigments in sputum and assessment of their contribution to sputum sol toxicity for respiratory epithelium

The phenazine pigments pyocyanin and 1-hydroxyphenazine were resolved by high-pressure liquid chromatography from the sputum sol phase from 9 of 13 patients with cystic fibrosis or bronchiectasis colonized by Pseudomonas aeruginosa. The concentrations measured were each sufficient to inhibit ciliary beating in vitro and contributed a significant proportion of sol phase toxicity for respiratory epithelium.

Measuring Friedreich ataxia: Interrater reliability of a neurologic rating scale

Measuring the severity of neurologic dysfunction in patients with inherited ataxias, including Friedreich ataxia (FA), is difficult because of the variable rate of progression, the variable age at onset and the variety of neural systems that may be affected. The authors discuss the problems related to rating scales in the ataxias, report a neurologic rating scale for FA, and demonstrate acceptable interrater reliability of the instrument.

Validation of the St. George's Respiratory Questionnaire in bronchiectasis

There is no disease-specific instrument available for health status assessment in bronchiectasis. We examined the stability, validity and responsiveness of a measure designed for asthma and COPD, the St. George's Respiratory Questionnaire (SGRQ), in this condition. One hundred and eleven patients were studied on 2 separate d 6 mo apart. On both days each patient completed the SGRQ and measures of general and disease-specific health, mood, and fatigue. They also performed a shuttle walking test and comprehensive lung function tests. Repeatability was tested over 2 wk in 23 patients. The intraclass correlation (ri) for the SGRQ Total score was 0.97. The SGRQ component scores correlated well with relevant markers of disease activity. Examples include: SGRQ Symptoms score versus MRC Wheeze score, r = 0.634, p < 0.0001; Activity score versus shuttle walking test, r = -0.659, p < 0.0001; and impacts score versus physical fatigue, r = 0.610, p < 0.0001. Changes in the SGRQ Total score from entry to follow-up also correlated with changes in other measures of the patients' health. There were significant differences in the SGRQ total score between patients who improved and those who deteriorated over the 6 mo in respect to wheeze (F = 5.6, p < 0.01) and breathlessness (F = 6.05, p < 0.01). We conclude that the SGRQ reflects impaired health in bronchiectasis patients.

Mortality in bronchiectasis: a long-term study assessing the factors influencing survival

There is little literature about the mortality associated with bronchiectasis. The aim of the present study was to investigate factors affecting mortality in patients with bronchiectasis. In total, 91 patients were examined for aetiology, pulmonary function tests, high-resolution computed tomography, sputum microbiology and quality of life scores and were then followed over 13 yrs. Overall, 29.7% of the patients died. On multivariate analysis, age, St George's Respiratory Questionnaire activity score, Pseudomonas aeruginosa infection, total lung capacity (TLC), residual volume/TLC and the transfer factor coefficient were all independently associated with mortality. In patients with moderate to severe bronchiectasis, mortality is associated with a degree of restrictive and obstructive disease, poor gas transfer and chronic pseudomonas infection. These features should guide future research into disease progression, and identify those patients needing intensive treatment.

MK2 Phosphorylates RIPK1 to Prevent TNF-Induced Cell Death

TNF is an inflammatory cytokine that upon binding to its receptor, TNFR1, can drive cytokine production, cell survival, or cell death. TNFR1 stimulation causes activation of NF-κB, p38α, and its downstream effector kinase MK2, thereby promoting transcription, mRNA stabilization, and translation of target genes. Here we show that TNF-induced activation of MK2 results in global RIPK1 phosphorylation. MK2 directly phosphorylates RIPK1 at residue S321, which inhibits its ability to bind FADD/caspase-8 and induce RIPK1-kinase-dependent apoptosis and necroptosis. Consistently, a phospho-mimetic S321D RIPK1 mutation limits TNF-induced death. Mechanistically, we find that phosphorylation of S321 inhibits RIPK1 kinase activation. We further show that cytosolic RIPK1 contributes to complex-II-mediated cell death, independent of its recruitment to complex-I, suggesting that complex-II originates from both RIPK1 in complex-I and cytosolic RIPK1. Thus, MK2-mediated phosphorylation of RIPK1 serves as a checkpoint within the TNF signaling pathway that integrates cell survival and cytokine production.

Primary ciliary dyskinesia: diagnosis and standards of care

Primary ciliary dyskinesia (PCD) is characterized by disease of the upper and lower respiratory tract, in association with visceral mirror image arrangement in 50% of cases, due to abnormal structure and/or function of cilia. The purpose of this paper is to review the clinical features, diagnosis and management of PCD. Presentations include neonatal respiratory distress, recurrent lower respiratory tract infection, chronic rhinosinusitis and male infertility. PCD enters the differential diagnosis of bronchiectasis, atypical asthma, and unusually severe upper airway disease. Diagnosis is by a cascade of investigations, starting with the saccharin test in patients older than 10 yrs; ciliary beat frequency and pattern on light microscopy; and electron microscopy to assess ciliary morphology and orientation. It is important not to confuse primary and secondary ciliary abnormalities. Nasal nitric oxide is low in PCD, and this measurement shows promise as a screening test for PCD. Diagnosis is important, in order to prevent the development of bronchiectasis and to avoid any unnecessary otorhinolaryngological procedures. Regular follow-up is essential, and management should be multidisciplinary, with input from centres with a special interest in PCD, having access to paediatric and adult chest physicians, otolaryngologists and audiological physicians, physiotherapists, counselling services and fertility clinics. The prognosis is good, but morbidity can be considerable if PCD is incorrectly managed.

Clinical and Molecular Analysis of Macrolide Resistance inMycobacterium aviumComplex Lung Disease

RATIONALE

The clinical features and outcome of macrolide-resistant Mycobacterium avium complex (MAC) lung disease are not known.

OBJECTIVES

Characterize patients, treatment, and isolates in macrolide-resistant MAC lung disease.

METHODS

Retrospective chart review, susceptibility testing, molecular fingerprinting, and DNA sequence analyses of resistant MAC isolates.

MEASUREMENTS AND MAIN RESULTS

We identified 51 patients over a 15-yr period with clarithromycin-resistant MAC (minimum inhibitory concentration (MIC)>or=32 microg/ml) lung disease at a single referral center. Twenty-four (47%) patients had nodular disease with bronchiectasis and 27 (53%) had upper lobe cavitary disease. Most patients (77%) had M. intracellulare. Sequencing of the 23S r-RNA gene showed 49 of 51 isolates (96%) with the expected mutation in adenine 2058 or 2059. Risk factors for resistance included macrolide monotherapy or combination with a quinolone only (39/51 or 76%). Macrolide resistance developed in 12 of 303 (4.0%) patients started on the American Thoracic Society-recommended two companion drugs, with no risk difference in clarithromycin versus azithromycin and daily versus intermittent therapy. Sputum conversion with macrolide-resistant MAC occurred in 11 of 14 (79%) patients who received more than 6 mo of injectable aminoglycoside therapy and lung resection, compared with 2 of 37 (5%) who did not. The 1-yr mortality in patients who remained culture positive was 34% (13/38) compared with 0% (0/13) of patients who became culture negative (converted).

CONCLUSIONS

Macrolide resistance rarely occurs in patients also receiving ethambutol and a rifamycin. Macrolide-resistant MAC lung disease requires aggressive drug and surgical therapy for cure.

The DIAP1 RING finger mediates ubiquitination of Dronc and is indispensable for regulating apoptosis

Members of the Inhibitor of Apoptosis Protein (IAP) family block activation of the intrinsic cell death machinery by binding to and neutralizing the activity of pro-apoptotic caspases. In Drosophila melanogaster, the pro-apoptotic proteins Reaper (Rpr), Grim and Hid (head involution defective) all induce cell death by antagonizing the anti-apoptotic activity of Drosophila IAP1 (DIAP1), thereby liberating caspases. Here, we show that in vivo, the RING finger of DIAP1 is essential for the regulation of apoptosis induced by Rpr, Hid and Dronc. Furthermore, we show that the RING finger of DIAP1 promotes the ubiquitination of both itself and of Dronc. Disruption of the DIAP1 RING finger does not inhibit its binding to Rpr, Hid or Dronc, but completely abrogates ubiquitination of Dronc. Our data suggest that IAPs suppress apoptosis by binding to and targeting caspases for ubiquitination.

A family of mammalian Fringe genes implicated in boundary determination and the Notch pathway

The formation of boundaries between groups of cells is a universal feature of metazoan development. Drosophila fringe modulates the activation of the Notch signal transduction pathway at the dorsal-ventral boundary of the wing imaginal disc. Three mammalian fringe-related family members have been cloned and characterized: Manic, Radical and Lunatic Fringe. Expression studies in mouse embryos support a conserved role for mammalian Fringe family members in participation in the Notch signaling pathway leading to boundary determination during segmentation. In mammalian cells, Drosophila fringe and the mouse Fringe proteins are subject to posttranslational regulation at the levels of differential secretion and proteolytic processing. When misexpressed in the developing Drosophila wing imaginal disc the mouse Fringe genes exhibit conserved and differential effects on boundary determination.

Failed intubation revisited: 17-yr experience in a teaching maternity unit

We have reviewed 5802 Caesarean sections performed during general anaesthesia. Our use of general anaesthesia had decreased from 83% in 1981 to 23% in 1994. Despite this, the incidence of failed intubation has increased from 1 in 1984 to 1 in 250 in 1994. The problems associated with general anaesthesia in the obstetric population are increasing. Asians and African/Afrocaribbeans were represented disproportionately because of the increased use of general anaesthesia in these patients. Exposure of trainees to obstetric general anaesthetics has decreased by one-third.

Pseudomonas aeruginosa pyocyanin and 1-hydroxyphenazine inhibit fungal growth

AIM

To examine strains of Pseudomonas aeruginosa for specific antifungal factors.

METHODS

Two clinical strains of P aeruginosa with strong in vitro inhibition (by cross streak assay) of Candida albicans and Aspergillus fumigatus were examined. Both strains were isolated from sputum--one from a patient with cystic fibrosis and one from a patient with bronchiectasis. Bacterial extracts were fractionated by high performance liquid chromatography and examined by ultraviolet absorbance and mass spectroscopy. Antifungal activity against C albicans and A fumigatus was determined in a well plate assay.

RESULTS

Pyocyanin was the major antifungal agent of P aeruginosa; 1-hydroxy-phenazine also possessed activity. Pyocyanin MICs for C albicans and A fumigatus were > 64 micrograms/ml. These phenazines were active against nine other yeast species pathogenic for man. Preliminary experiments also suggested possible inhibition of yeast mycelial transformation in C albicans by pyocyanin.

CONCLUSIONS

There may be a role for pyocyanin and 1-hydroxyphenazine in the prevention of pulmonary candidiasis in patients colonised by P aeruginosa.

Degradation of DIAP1 by the N-end rule pathway is essential for regulating apoptosis

Some members of the inhibitor of apoptosis (IAP) protein family block apoptosis by binding to and neutralizing active caspases. We recently demonstrated that a physical association between IAP and caspases alone is insufficient to regulate caspases in vivo and that an additional level of control is provided by IAP-mediated ubiquitination of both itself and the associated caspases. Here we show that Drosophila IAP 1 (DIAP1) is degraded by the 'N-end rule' pathway and that this process is indispensable for regulating apoptosis. Caspase-mediated cleavage of DIAP1 at position 20 converts the more stable pro-N-degron of DIAP1 into the highly unstable, Asn-bearing, DIAP1 N-degron of the N-end rule degradation pathway. Thus, DIAP1 represents the first known metazoan substrate of the N-end rule pathway that is targeted for degradation through its amino-terminal Asn residue. We demonstrate that the N-end rule pathway is required for regulation of apoptosis induced by Reaper and Hid expression in the Drosophila melanogaster eye. Our data suggest that DIAP1 instability, mediated through caspase activity and subsequent exposure of the N-end rule pathway, is essential for suppression of apoptosis. We suggest that DIAP1 safeguards cell viability through the coordinated mutual destruction of itself and associated active caspases.