Diagnostic utility and reporting recommendations for clinical DNA methylation episignature testing in genetically undiagnosed rare diseases

PURPOSE

This study aims to assess the diagnostic utility and provide reporting recommendations for clinical DNA methylation episignature testing based on the cohort of patients tested through the EpiSign Clinical Testing Network.

METHODS

The EpiSign assay utilized unsupervised clustering techniques and a support vector machine-based classification algorithm to compare each patient's genome-wide DNA methylation profile with the EpiSign Knowledge Database, yielding the result that was reported. An international working group, representing distinct EpiSign Clinical Testing Network health jurisdictions, collaborated to establish recommendations for interpretation and reporting of episignature testing.

RESULTS

Among 2399 cases analyzed, 1667 cases underwent a comprehensive screen of validated episignatures, imprinting, and promoter regions, resulting in 18.7% (312/1667) positive reports. The remaining 732 referrals underwent targeted episignature analysis for assessment of sequence or copy-number variants (CNVs) of uncertain significance or for assessment of clinical diagnoses without confirmed molecular findings, and 32.4% (237/732) were positive. Cases with detailed clinical information were highlighted to describe various utility scenarios for episignature testing.

CONCLUSION

Clinical DNA methylation testing including episignatures, imprinting, and promoter analysis provided by an integrated network of clinical laboratories enables test standardization and demonstrates significant diagnostic yield and clinical utility beyond DNA sequence analysis in rare diseases.

Systematic identification of disease-causing promoter and untranslated region variants in 8,040 undiagnosed individuals with rare disease

Background

Both promoters and untranslated regions (UTRs) have critical regulatory roles, yet variants in these regions are largely excluded from clinical genetic testing due to difficulty in interpreting pathogenicity. The extent to which these regions may harbour diagnoses for individuals with rare disease is currently unknown.

Methods

We present a framework for the identification and annotation of potentially deleterious proximal promoter and UTR variants in known dominant disease genes. We use this framework to annotate de novo variants (DNVs) in 8,040 undiagnosed individuals in the Genomics England 100,000 genomes project, which were subject to strict region-based filtering, clinical review, and validation studies where possible. In addition, we performed region and variant annotation-based burden testing in 7,862 unrelated probands against matched unaffected controls.

Results

We prioritised eleven DNVs and identified an additional variant overlapping one of the eleven. Ten of these twelve variants (82%) are in genes that are a strong match to the individual's phenotype and six had not previously been identified. Through burden testing, we did not observe a significant enrichment of potentially deleterious promoter and/or UTR variants in individuals with rare disease collectively across any of our region or variant annotations.

Conclusions

Overall, we demonstrate the value of screening promoters and UTRs to uncover additional diagnoses for previously undiagnosed individuals with rare disease and provide a framework for doing so without dramatically increasing interpretation burden.

The subclonal complexity of STIL-TAL1+ T-cell acute lymphoblastic leukaemia

Single-cell genetics were used to interrogate clonal complexity and the sequence of mutational events in STIL-TAL1+ T-ALL. Single-cell multicolour FISH was used to demonstrate that the earliest detectable leukaemia subclone contained the STIL-TAL1 fusion and copy number loss of 9p21.3 (CDKN2A/CDKN2B locus), with other copy number alterations including loss of PTEN occurring as secondary subclonal events. In three cases, multiplex qPCR and phylogenetic analysis were used to produce branching evolutionary trees recapitulating the snapshot history of T-ALL evolution in this leukaemia subtype, which confirmed that mutations in key T-ALL drivers, including NOTCH1 and PTEN, were subclonal and reiterative in distinct subclones. Xenografting confirmed that self-renewing or propagating cells were genetically diverse. These data suggest that the STIL-TAL1 fusion is a likely founder or truncal event. Therapies targeting the TAL1 auto-regulatory complex are worthy of further investigation in T-ALL.

Vulval Crohn's disease – a multi-specialty approach

We report a case of Crohn's disease where the patient initially presented with vulval ulceration to the gynaecology unit. Initial investigations were planned jointly by both the gynaecology and genitourinary medicine staff. An examination under general anaesthetic by both teams was performed and biopsies taken. These showed a chronic inflammatory process with epithelioid granulomas. The teams then referred the case to the dermatology team who made the diagnosis of vulval Crohn's disease and initiated treatment with prednisolone and azathioprine. The case illustrates the need for a multi-speciality approach when dealing with such cases.

Impact of PTEN abnormalities on outcome in pediatric patients with T-cell acute lymphoblastic leukemia treated on the MRC UKALL2003 trial

PTEN gene inactivation by mutation or deletion is common in pediatric T-cell acute lymphoblastic leukemia (T-ALL), but the impact on outcome is unclear, particularly in patients with NOTCH1/FBXW7 mutations. We screened samples from 145 patients treated on the MRC UKALL2003 trial for PTEN mutations using heteroduplex analysis and gene deletions using single nucleotide polymorphism arrays, and related genotype to response to therapy and long-term outcome. PTEN loss-of-function mutations/gene deletions were detected in 22% (PTEN(ABN)). Quantification of mutant level indicated that 67% of mutated cases harbored more than one mutant, with up to four mutants detected, consistent with the presence of multiple leukemic sub-clones. Overall, 41% of PTEN(ABN) cases were considered to have biallelic abnormalities (mutation and/or deletion) with complete loss of PTEN in a proportion of cells. In addition, 9% of cases had N- or K-RAS mutations. Neither PTEN nor RAS genotype significantly impacted on response to therapy or long-term outcome, irrespective of mutant level, and there was no evidence that they changed the highly favorable outcome of patients with double NOTCH1/FBXW7 mutations. These results indicate that, for pediatric patients treated according to current protocols, routine screening for PTEN or RAS abnormalities at diagnosis is not warranted to further refine risk stratification.

Simpson's Paradox and the Impact of Different DNMT3A Mutations on Outcome in Younger Adults With Acute Myeloid Leukemia

PURPOSE

To evaluate the impact of DNMT3A mutations on outcome in younger patients with cytogenetic intermediate-risk acute myeloid leukemia.

PATIENTS AND METHODS

Diagnostic samples from 914 patients (97% < 60 years old) were screened for mutations in DNMT3A exons 13 to 23. Clinical outcome was evaluated according to presence or absence of a mutation and stratified according to type of mutation (R882, non-R882 missense, or truncation).

RESULTS

DNMT3A mutations (DNMT3A(MUT)) were identified in 272 patients (30%) and associated with a poorer prognosis than wild-type DNMT3A, but the difference was only seen when the results were stratified according to NPM1 genotype. This example of Simpson's paradox results from the high coincidence of DNMT3A and NPM1 mutations (80% of patients with DNMT3A(MUT) had NPM1 mutations), where the two mutations have opposing prognostic impact. In the stratified analyses, relapse in patients with DNMT3A(MUT) was higher (hazard ratio, 1.35; 95% CI, 1.07 to 1.72; P = .01), and overall survival was lower (hazard ratio, 1.37; 95% CI, 1.12 to 1.87; P = .002). The impact of DNMT3A(MUT) did not differ according to NPM1 genotype (test for heterogeneity: relapse, P = .4; overall survival, P = .9). Further analysis according to the type of DNMT3A mutation indicated that outcome was comparable in patients with R882 and non-R882 missense mutants, whereas in those with truncation mutants, it was comparable to wild-type DNMT3A.

CONCLUSION

These data confirm that presence of a DNMT3A mutation should be considered as a poor-risk prognostic factor, irrespective of the NPM1 genotype, and suggest that further consideration should be given to the type of DNMT3A mutation.

Cyclin C is a haploinsufficient tumour suppressor

Cyclin C was cloned as a growth-promoting G1 cyclin, and was also shown to regulate gene transcription. Here we report that in vivo cyclin C acts as a haploinsufficient tumour suppressor, by controlling Notch1 oncogene levels. Cyclin C activates an 'orphan' CDK19 kinase, as well as CDK8 and CDK3. These cyclin-C-CDK complexes phosphorylate the Notch1 intracellular domain (ICN1) and promote ICN1 degradation. Genetic ablation of cyclin C blocks ICN1 phosphorylation in vivo, thereby elevating ICN1 levels in cyclin-C-knockout mice. Cyclin C ablation or heterozygosity collaborates with other oncogenic lesions and accelerates development of T-cell acute lymphoblastic leukaemia (T-ALL). Furthermore, the cyclin C encoding gene CCNC is heterozygously deleted in a significant fraction of human T-ALLs, and these tumours express reduced cyclin C levels. We also describe point mutations in human T-ALL that render cyclin-C-CDK unable to phosphorylate ICN1. Hence, tumour cells may develop different strategies to evade inhibition by cyclin C.

The human ether-a'-go-go related gene (hERG) K+ channel blockade by the investigative selective-serotonin reuptake inhibitor CONA-437: limited dependence on S6 aromatic residues

Diverse non-cardiac drugs adversely influence cardiac electrophysiology by inhibiting repolarising K(+) currents mediated by channels encoded by the human ether-a-go-go-related gene (hERG). In this study, pharmacological blockade of hERG K(+) channel current (I(hERG)) by a novel investigative serotonin-selective reuptake inhibitor (SSRI), CONA-437, was investigated. Whole-cell patch-clamp measurements of I(hERG) were made from human embryonic kidney (HEK 293) cells expressing wild-type (WT) or mutant forms of the hERG channel. With a step-ramp voltage-command, peak I(hERG) was inhibited with an IC(50) of 1.34 μM at 35 ±1°C; the IC(50) with the same protocol was not significantly different at room temperature. Voltage-command waveform selection had only a modest effect on the potency of I(hERG) block: the IC50 with a ventricular action potential command was 0.72 μM. I(hERG) blockade developed rapidly with time following membrane depolarisation and showed a weak dependence on voltage, accompanied by a shift of ≈ -5 mV in voltage-dependence of activation. There was no significant effect of CONA-437 on voltage-dependence of I(hERG) inactivation, though at some voltages an apparent acceleration of the time-course of inactivation was observed. Significantly, mutation of the S6 aromatic amino acid residues Y652 and F656 had only a modest effect on I(hERG) blockade by CONA-437 (a 3-4 fold shift in affinity). CONA-437 at up to 30 μM had no significant effect on either Nav1.5 sodium channels or L-type calcium channels. In conclusion, the novel SSRI CONA-437 is particularly notable as a gating-dependent hERG channel inhibitor for which neither S6 aromatic amino-acid constituent of the canonical drug binding site on the hERG channel appears obligatory for I(hERG) inhibition to occur.

Impact of NOTCH1/FBXW7 mutations on outcome in pediatric T-cell acute lymphoblastic leukemia patients treated on the MRC UKALL 2003 trial

Activating mutations in the NOTCH1 pathway are frequent in pediatric T-cell acute lymphoblastic leukemia (T-ALL) but their role in refining risk stratification is unclear. We screened 162 pediatric T-ALL patients treated on the MRC UKALL2003 trial for NOTCH1/FBXW7 gene mutations and related genotype to response to therapy and long-term outcome. Overall, 35% were wild-type (WT) for both genes (NOTCH1(WT)FBXW7(WT)), 38% single NOTCH1 mutant (NOTCH1(Single)FBXW7(WT)), 3% just FBXW7 mutant (NOTCH1(WT)FBXW7(MUT)) and 24% either double NOTCH1 mutant (NOTCH1(Double)FBXW7(WT)) or mutant in both genes (NOTCH1(MUT)FBXW7(MUT)), hereafter called as NOTCH1±FBXW7(Double). There was no difference between groups in early response to therapy, but NOTCH1±FBXW7(Double) patients were more likely to be associated with negative minimal residual disease (MRD) post-induction than NOTCH1(WT)FBXW7(WT) patients (71% versus 40%, P=0.004). Outcome improved according to the number of mutations, overall survival at 5 years 82%, 88% and 100% for NOTCH1(WT)FBXW7(WT), NOTCH1(Single)FBXW7(WT) and NOTCH1±FBXW7(Double) patients, respectively (log-rank P for trend=0.005). Although 14 NOTCH1±FBXW7(Double) patients were classified as high risk (slow response and/or MRD positive), only two had disease progression and all remain alive. Patients with double NOTCH1 and/or FBXW7 mutations have a very good outcome and should not be considered for more intensive therapy in first remission, even if slow early responders or MRD positive after induction therapy.

PI3K/mTOR inhibition upregulates NOTCH-MYC signalling leading to an impaired cytotoxic response

PI3K, mTOR and NOTCH pathways are frequently dysregulated in T-cell acute lymphoblastic leukaemia (T-ALL). Blockade of PI3K and mTOR with the dual inhibitor PI-103 decreased proliferation in all 15 T-ALL cell lines tested, inducing cell death in three. Combined PI3K/mTOR/NOTCH inhibition (with a γ-secretase inhibitor (GSI)) led to enhanced cell-cycle arrest and to subsequent cell death in 7/11 remaining NOTCH mutant cell lines. Commitment to cell death occurred within 48-72 h and was maximal when PI3K, mTOR and NOTCH activities were inhibited. PI-103 addition led to upregulation of c-MYC, which was blocked by coincubation with a GSI, indicating that PI3K/mTOR inhibition resulted in activation of the NOTCH-MYC pathway. Microarray studies showed a global increase in NOTCH target gene expression upon PI3K/mTOR inhibition. NOTCH-MYC-induced resistance to PI3K/mTOR inhibition was supported by synergistic cell death induction by PI-103 and a small molecule c-MYC inhibitor, and by reduction of the cytotoxic effect of PI-103+GSI by c-MYC overexpression. These results show that drugs targeting PI3K/mTOR can upregulate NOTCH-MYC activity, have implications for the use of PI3K inhibitors for the treatment of other malignancies with activated NOTCH, and provide a rational basis for the use of drug combinations that target both the pathways.

Prognostic implications of NOTCH1 and FBXW7 mutations in adults with T-cell acute lymphoblastic leukemia treated on the MRC UKALLXII/ECOG E2993 protocol

PURPOSE

Notch pathway activation by mutations in either NOTCH1 and/or FBXW7 is one of the most common molecular events in T-cell acute lymphoblastic leukemia (T-ALL) and, in pediatric disease, predicts for favorable outcome. Their prognostic significance in adult T-ALL is unclear. We sought to evaluate the outcome according to mutation status of patients with adult T-ALL treated on the United Kingdom Acute Lymphoblastic Leukaemia XII (UKALLXII)/Eastern Cooperative Oncology Group (ECOG) E2993 protocol.

METHODS

NOTCH1 and FBXW7 were screened by a combination of denaturing high-performance liquid chromatography and sequencing in 88 adult patients with T-ALL treated on the UKALLXII/ECOG E2993 protocol and compared with clinical characteristics and outcome.

RESULTS

NOTCH1 and FBXW7 mutations were common (60% and 18%, respectively) and were not associated with age or WBC count. NOTCH1 heterodimerization domain mutations were associated with FBXW7 mutations (P = .02), and NOTCH1 proline, glutamic acid, serine, threonine (PEST) rich domain and FBXW7 mutations were mutually exclusive. There were an equal number of high- and standard-risk patients in the NOTCH1 and FBXW7 mutated (MUT) groups. Patients wild type (WT) for both markers trended toward poorer event-free survival (EFS; MUT v WT, 51% v 27%, P = .10; hazard ratio, 0.6). Analysis by each marker individually was not significantly predictive of outcome (NOTCH1 MUT v WT, EFS 49% v 34%, P = .20; FBXW7 MUT v WT, EFS 53% v 41%, P.72).

CONCLUSION

NOTCH1 and FBXW7 mutant-positive patients do not fare sufficiently well to warrant an individualized treatment approach in future studies.

Regulation of 15-lipoxygenase isozymes and mucin secretion by cytokines in cultured normal human bronchial epithelial cells

OBJECTIVE AND DESIGN

To study the effects of IL-4, IL-13, IL-1beta, IL-8 and TNFalpha on 15-lipoxygenase(15-LO) isozyme expression and mucin secretion in normal human bronchial epithelial cells.

MATERIAL AND METHODS

The effects of IL-4, IL-13, IL-1beta, IL-8 and TNFalpha on 15-LO isoenzyme mRNA and protein expression, total 15-LO enzyme activity and mucin secretion were examined in cultures of normal human bronchial epithelial cells. In addition, in order to determine whether the observed effects on mucin secretion were due to lipoxygenase (LO) products, the effect of the non-selective LO inhibitor nordihydroguaiaretic acid was examined.

RESULTS

IL-4 and IL- 13 selectively enhanced 15-LOa mRNA and protein levels, and total 15-LO enzyme activity. In contrast, no changes were observed in 15-LOb mRNA or protein levels. IL-4 and IL-13 both reduced mucin secretion in this cell type, however the non-selective LO inhibitor nordihydroguaiaretic acid had no effect on this action of IL-4.

CONCLUSIONS

These data demonstrate that IL-4 and IL-13 selectively regulate the expression of the 15-LOa isozyme. However, 15LOa products do not mediate the IL-4-induced reduction in mucin secretion observed in this cell type.

Potassium ion- and nitric oxide-induced exocytosis from populations of hippocampal synapses during synaptic maturation in vitro

The development of mechanisms of neurotransmitter release is an important component in the formation of functional synaptic connections. Synaptic neurotransmitter release can be modulated by nitric oxide, a compound shown to have a variety of physiologic functions in the nervous system. The goal of this study was to determine whether, during synaptic maturation, nitric oxide is capable of affecting exocytosis of synaptic vesicles, and to compare its effects with those elicited by strongly depolarizing stimuli. To address these questions we examined vesicle release from large numbers of individual synapses of hippocampal neurons between five and 13 days in culture. Synaptic vesicles were labelled by uptake of the styrylpyridinium dye N-(3-triethylammoniumpropyl)-4-(4-(dibutylamino)styryl)pyridinium dibromide (FM1-43) and their release was monitored by fluorescence imaging. Across populations of developing synapses, there was a good correspondence between FM1-43 staining and synapsin immunocytochemistry. A marked heterogeneity was observed in the ability to release vesicles both after potassium and nitric oxide stimulation. In less mature populations of synapses, the rate of potassium- and nitric oxide-induced exocytosis gradually increased, while at later stages nitric oxide-induced responses levelled off and potassium-induced responses continued to rise. Application of nitric oxide donors did not trigger any detectable changes in intracellular calcium. Combined immunocytochemical analysis of cultured hippocampal neurons for neuronal nitric oxide synthase and synapsin revealed that nitric oxide synthase was present within neurites of cultured hippocampal neurons, largely distributed in a bead-like pattern which partially overlapped presynaptic sites. Stimulation of the N-methyl-D-aspartate receptor while blocking propagation of action potentials with tetrodotoxin resulted in exocytosis from numerous individually resolved sites. Preincubation of neurons with an nitric oxide synthase inhibitor or addition of an nitric oxide scavenger eliminated these responses indicating a role for nitric oxide in N-methyl-D-aspartate-stimulated exocytosis. Using fluorescence imaging of individually resolved synaptic sites, we provide direct evidence for an effect of nitric oxide on vesicular neurotransmitter release in intact neurons. Nitric oxide is capable to produce this effect at all stages of synaptic development and acts independently of calcium influx. We show that nitric oxide synthase is present at synaptic sites and endogenously produced nitric oxide is sufficient to cause exocytosis. Taken together, these experiments suggest a possible role for nitric oxide in calcium-independent transmitter release in populations of synapses at all stages of maturation.

Silencer elements modulate the expression of the gene for the neuron-glia cell adhesion molecule, Ng-CAM

The combined factors that regulate the expression of cell adhesion molecules (CAMs) during development of the nervous system are largely unknown. To identify such factors for Ng-CAM, the neuron-glia CAM, constructs containing portions of the 5' end of the Ng-CAM gene were examined for activity after transfection into N2A neuroblastoma and NIH3T3 cells. Positive regulatory elements active in both cell types included an Ng-CAM proximal promoter with SP1 and cAMP response element motifs extending 447 base pairs upstream of a single RNA start site and a region within the first exon corresponding to 5'-untranslated sequences. Negative regulatory elements included five neuron-restrictive silencer elements (NRSEs) and a binding site for Pax gene products in a 305-base pair segment of the first intron. Constructs containing the promoter together with the entire first intron were active in N2A cells but were silenced in NIH3T3 cells. This silencer activity was mapped to the NRSEs. In contrast, the Pax motif inhibited activity of Ng-CAM constructs in both cell types. The DNA elements defined in these transfection experiments were examined for their ability to bind nuclear factors. The region within the first exon formed a DNA-protein complex after exposure to nuclear extracts prepared from both NIH3T3 and N2A cells. The NRSE region formed a more prominent complex with proteins prepared from NIH3T3 cells than it did with extracts from N2A cells. A member of the Pax protein family, Pax-3 bound to the Pax motif. Mutations introduced within the Pax motif in its ATTA sequence eliminated this binding whereas mutations in its GTTCC sequence did not, suggesting that paired homeodomain interactions are important for the recognition of Pax-3 by this DNA target sequence. The combined data suggest that negative regulation by NRSEs and Pax proteins may play a key role in the place-dependent expression patterns of Ng-CAM during development.

Structural and functional similarities between the promoters for mouse tenascin and chicken cytotactin

Cytotactin/tenascin is an extracellular matrix glycoprotein expressed in a restricted anteroposterior pattern during vertebrate development and is reexpressed in the adult during wound healing, tumorigenesis, and nerve regeneration. Previously, we have characterized the chicken cytotactin promoter and have shown its regulation by homeobox gene products in vitro. We have now isolated the promoter for the mouse tenascin gene in order to determine whether common or different DNA regulatory elements control the expression of this gene in these two species. Like the chicken cytotactin gene, the mouse tenascin gene has a single RNA start site that lies 27 bp downstream of a TATA box. A 4028-bp region of DNA upstream of the mouse tenascin gene was sequenced and examined for regulatory motifs in common with the upstream sequence from the chicken cytotactin promoter. Two hundred thirty base pairs of the proximal promoter regions from both genes had an extended sequence similarity and contained common regulatory motifs such as two tracts of homopolymeric dA.dT sequence, an octamer motif, an ATTA (TAAT) motif which is a common core sequence for binding of homeodomain transcription factors, and a TATA-box/cap-site region. Reporter gene constructs with various 5' deletions of the mouse tenascin upstream sequence were tested in transient transfections of mouse NIH 3T3 and chicken embryo fibroblasts. The conserved proximal promoter region of tenascin was responsible for most of the positive regulatory activity. In addition, an upstream region (-2478 to -247) repressed proximal promoter activity in mouse fibroblasts and also in chicken embryo fibroblasts. These data indicate that both the structure and function of the cytotactin/tenascin proximal promoters have remained conserved over 250 million years.

Disruption by lithium of phosphatidylinositol-4,5-bisphosphate supply and inositol-1,4,5-trisphosphate generation in Chinese hamster ovary cells expressing human recombinant m1 muscarinic receptors

Inhibitory effects of the anti-manic agent lithium on carbachol-stimulated phosphoinositide signaling have been investigated in Chinese hamster ovary (CHO) cells transfected with human m1 muscarinic receptor cDNA (Bmax, 816 fmol/mg of protein). In the presence of Li+, a time-dependent inhibition of inositol-1,4,5-trisphosphate [Ins(1,4,5)P3] mass accumulation was observed within 10 min of agonist addition (IC50 for lithium inhibition at 20 min after carbachol addition, 0.5 mM). The Li(+)-induced decrease in agonist-stimulated Ins(1,4,5)P3 levels was preceded by a dramatic increase in CMP-phosphatidate accumulation. The idea that Li+ blockade of inositol monophosphatase caused a rapid depletion of the cellular myo-inositol pool in CHO-m1 cells was supported by the reversal of Li+ effects by exogenous myo-inositol. Carbachol (1 mM) alone caused a rapid and dramatic decrease in phosphatidylinositol-4,5-bisphosphate [PtdIns(4,5)-P2]in CHO-m1 cells labeled to equilibrium with [3H]-inositol. Carbachol-evoked decreases in PtdIns(4,5)P2 were time-dependently accentuated by Li+ (IC50 for Li+ inhibition at 20 min after carbachol addition, 1.2 mM). Measurements of changes in PtdIns(4,5)P2 mass demonstrated that the effect of Li+ was completely and concentration-dependently reversed by addition of myo-inositol. Sequential 30-min periods of carbachol stimulation resulted in similar time courses of Ins(1,4,5)P3 accumulation when an intervening 20-min recovery period was included in the protocol. Inclusion of Li+ throughout resulted in a more rapid and dramatic attenuation of Ins(1,4,5)P3 during the agonist rechallenge period, which could be correlated with accentuated changes in PtdIns(4,5)P2. These data demonstrate that, although mechanisms operate to efficiently resynthesize PtdIns(4,5)P2, the temporal correlation of carbachol-evoked decreases in PtdIns(4,5)P2 levels in the presence of Li+ strongly suggests that phosphoinositide-specific phospholipase C substrate depletion may be causal in the subsequent decrease in Ins(1,4,5)P3 levels.

Natural history and course of acquired lactic acidosis in adults. DCA-Lactic Acidosis Study Group

STUDY OBJECTIVE

To determine the pathogenesis and clinical course of lactic acidosis in adults receiving standard medical care.

DESIGN

Placebo arm of a 5-year prospective, randomized, blinded study comparing placebo and dichloroacetate as specific lactate-lowering therapy. Each patient received intravenous saline placebo in addition to conventional therapy.

SETTING

Intensive care units of 10 tertiary care hospitals in North America.

PATIENTS

One hundred twenty-six patients with lactic acidosis, defined as arterial blood lactate greater than or equal to 5 mmol/L and either arterial pH of less than or equal to 7.35 or base deficit greater than 6 mmol/L. Patients were followed for up to 6 months.

MEASUREMENTS AND MAIN RESULTS

Mean +/- SD demographic entry data for 126 patients included: age 56 +/- 17 years, lactate 10.4 +/- 5.5 mmol/L, pH 7.24 +/- 0.14, calculated base deficit 14.1 +/- 5.4, arterial systolic blood pressure 103 +/- 29 mm Hg, Glasgow Coma score 7.9 +/- 4.9, and APACHE II score 19.2 +/- 8.1. Despite fluids and pressors, 32% of patients had systolic blood pressures of less than or equal to 90 mm Hg in association with sepsis (59%), cardiac failure (18%), or hemorrhage (18%). The most common causes of lactic acidosis in the absence of shock were sepsis (49%), liver disease (15%), and respiratory failure (12%). The median survival was 38.5 hours. Survival at 24 hours was 59%. Arterial pH predicted 24-hour survival better than base deficit or bicarbonate level. Percent survival was 41% at 3 days and 17% at 30 days. Only 21% of patients survived to leave the intensive care unit, and 17% were discharged from the hospital. In patients receiving sodium bicarbonate, neither acid-base nor hemodynamic status improved.

CONCLUSIONS

In this first prospective study of the clinical course of acute lactic acidosis in adults, nearly all subjects had both hemodynamic and nonhemodynamic (metabolic) underlying causes, many of which independently predicted survival and most of which were refractory to standard care.

Who chooses to have the HIV antibody test in the antenatal clinic?

With the increase in human immunodeficiency virus (HIV) seroprevalence amongst antenatal clinic attenders, and given that current medical opinion considers it desirable that a woman is aware of her serostatus, it has been recommended that the HIV test is offered to all women in the antenatal clinic and that its uptake is monitored. This paper reports on the uptake rate during the 12 months to February 1990 at a central London hospital, which was 17%, and the characteristics of the women who agreed to be tested for HIV. Using information collected by the midwife on an interactive computer during the 'booking' interview, it was found that women who were single and not in a stable relationship (p < 0.001) and those who described themselves as Mediterranean (p < 0.01) were more likely to accept the test. Caucasian women (p < 0.05) and married women (p < 0.05) were less likely to accept the test. Accepters did not differ from decliners in any other variable examined. Possible reasons for these differences are discussed.

Molecular genetic studies of sporadic pituitary tumors

Tumor formation may result from the activation of dominant oncogenes or by inactivation of recessive, tumor suppressor genes. The role of such mutations in the development of pituitary tumors has been studied. Tumors from 88 patients, representing the 4 major classes of adenoma, were investigated. In DNA extracted from matched leukocyte and tumor samples, allelic deletions were sought with 15 probes identifying restriction fragment length polymorphisms on chromosomes 1, 5, 10, 11, 13, 17, 20, and 22. Evidence of amplification or rearrangement of 10 recognized cellular oncogenes (N-ras, mycL1, mycN, myc, H-ras, bcl1, H-stf1, sea, kraS2, and fos) was sought in tumor DNA. Activating dominant mutations of Gs alpha were detected using the polymerase chain reaction to amplify exons 7-10 and hybridizing the product to normal and mutant allele-specific oligonucleotides. Allelic deletions on chromosome 11 were identified in 16 tumors (18%) representing all 4 major subtypes. Deletions on other autosomes were observed in less than 6% of tumors. Three adenomas had deletions on multiple autosomes, 2 of these were aggressive and recurrent. Mutations of Gs alpha were confirmed to be specific to somatotrophinomas, being identified in 36% of such tumors in this series. No evidence of amplification or rearrangement of other recognized cellular oncogenes was found. Inactivation of a recessive oncogene on chromosome 11 is an important and possibly early event in the development of the four major types of pituitary adenoma, whereas activating mutations of Gs alpha are confirmed to be specific to somatotropinomas. Two aggressive tumors were found to have multiple autosomal losses, suggesting a multistep progression in the development of tumors of this phenotype.

Comparative effects of lithium on the phosphoinositide cycle in rat cerebral cortex, hippocampus, and striatum

The effects of lithium on muscarinic cholinoceptor-stimulated phosphoinositide turnover have been investigated in rat hippocampal, striatal, and cerebral cortical slices using [3H]inositol or [3H]cytidine prelabelling and inositol 1,4,5-trisphosphate [Ins(1,4,5)P3] and inositol 1,3,4,5-tetrakisphosphate [Ins(1,3,4,5)P4] mass determination methods. Carbachol addition resulted in maintained increases in Ins(1,4,5)P3 and Ins(1,3,4,5)P4 mass levels in hippocampus and cerebral cortex, whereas in striatal slices these responses declined significantly over a 30-min incubation period. Carbachol-stimulated Ins(1,4,5)P3 and Ins(1,3,4,5)P4 accumulations were inhibited by lithium in all brain regions studied in a time- and concentration-dependent manner. For example, in hippocampal slices significant inhibitory effects of LiCl were observed at times > 10 min after agonist challenge; IC50 values for inhibition of agonist-stimulated Ins(1,4,5)P3 and Ins(1,3,4,5)P4 accumulations by lithium were 0.22 +/- 0.09 and 0.33 +/- 0.13 mM, respectively. [3H]CMP-phosphatidate accumulation increased in all brain regions when slices were stimulated by agonist and lithium. The ability of myo-inositol to reverse these effects, as well as lithium-suppressed Ins(1,4,5)P3 accumulation, implicates myo-inositol depletion in the action of lithium in the hippocampus and cortex at least. The results of this study suggest that although significant differences in the magnitude and time courses of changes in inositol (poly)phosphate metabolites occur in different brain regions, lithium evokes qualitatively similar enhancements of [3H]inositol monophosphate and [3H]-CMP-phosphatidate levels and inhibitions of Ins(1,4,5)P3 and Ins(1,3,4,5)P4 accumulations. However, the inability of striatal slices to sustain carbachol-stimulated inositol polyphosphate accumulation in the absence of lithium and the inability to reverse effects with myo-inositol may indicate differences in phosphoinositide signalling in this brain region.

The interaction between noradrenaline and ATP upon polyphosphoinositide metabolism and contraction in tail arteries from normo- and hypertensive rats

The effects of, and interaction between, noradrenaline and alpha,beta-methylene ATP upon polyphosphoinositide (PPI) breakdown, investigated by measuring the accumulation of inositol phosphates, and contraction, were studied in tail arteries from normo- (WKY) and spontaneously-hypertensive (SHR) rats. Noradrenaline (10(-7)-10(-3) M) evoked a prazosin (10(-6) M)-sensitive, concentration-dependent increase in total inositol phosphate accumulation in both WKY and SHR rats. No significant differences were observed in either the maximal response or in the concentration range over which noradrenaline evoked this response, between these two populations. Noradrenaline (5 x 10(-7)-5 x 10(-5) M) evoked a concentration-dependent contraction of arteries from both SHR and WKY rats. The responses to noradrenaline were about 2-fold greater at all effective concentrations of noradrenaline in SHR compared with WKY rats. alpha,beta-Methylene ATP (10(-6) M) did not alter noradrenaline-stimulated total inositol phosphate accumulation, in arteries from either SHR or WKY rats, measured either as the maximal response or as the EC50. alpha,beta-Methylene ATP (5 x 10(-6) M), by itself, evoked a contractile response, which was quantitatively similar in SHR and WKY rats, and was additive with the contractile responses to noradrenaline (5 x 10(-7)-5 x 10(-5) M). The maximum response produced by a combination of noradrenaline and alpha,beta-Methylene ATP was quantitatively similar to that produced by noradrenaline alone. No evidence of synergism between alpha,beta-Methylene ATP and noradrenaline upon contraction was observed.(ABSTRACT TRUNCATED AT 250 WORDS)

A controlled clinical trial of dichloroacetate for treatment of lactic acidosis in adults. The Dichloroacetate-Lactic Acidosis Study Group

BACKGROUND

Mortality is very high in lactic acidosis, and there is no satisfactory treatment other than treatment of the underlying cause. Uncontrolled studies have suggested that dichloroacetate, which stimulates the oxidation of lactate to acetyl-coenzyme A and carbon dioxide, might reduce morbidity and improve survival among patients with this condition.

METHODS

We conducted a placebo-controlled, randomized trial of intravenous sodium dichloroacetate therapy in 252 patients with lactic acidosis; 126 were assigned to receive dichloroacetate and 126 to receive placebo. The entry criteria included an arterial-blood lactate concentration of > or = 5.0 mmol per liter and either an arterial-blood pH of < or = 7.35 or a base deficit of > or = 6 mmol per liter. The mean (+/- SD) arterial-blood lactate concentrations before treatment were 11.6 +/- 7.0 mmol per liter in the dichloroacetate-treated patients and 10.4 +/- 5.5 mmol per liter in the placebo group, and the mean initial arterial-blood pH values were 7.24 +/- 0.12 and 7.24 +/- 0.13, respectively. Eighty-six percent of the patients required mechanical ventilation, and 74 percent required pressor agents, inotropic drugs, or both because of hypotension.

RESULTS

The arterial-blood lactate concentration decreased 20 percent or more in 83 (66 percent) of the 126 patients who received dichloroacetate and 45 (36 percent) of the 126 patients who received placebo (P = 0.001). The arterial-blood pH also increased more in the dichloroacetate-treated patients (P = 0.005). The absolute magnitude of the differences was small, however, and they were not associated with improvement in hemodynamics or survival. Only 12 percent of the dichloroacetate-treated patients and 17 percent of the placebo patients survived to be discharged from the hospital.

CONCLUSIONS

Dichloroacetate treatment of patients with severe lactic acidosis results in statistically significant but clinically unimportant changes in arterial-blood lactate concentrations and pH and fails to alter either hemodynamics or survival.

Evidence for lithium-sensitive inositol 4,5-bisphosphate accumulation in muscarinic cholinoceptor-stimulated cerebral-cortex slices

Stimulation of [3H]inositol-prelabelled rat cerebral-cortex slices with carbachol results in the accumulation of four [3H]inositol bisphosphate isomeric species, Ins(1,3)P2, Ins(1,4)P2, Ins(3,4)P2 and Ins(4,5)P2. Although the last isomer ran as a minor peak on h.p.l.c., its accumulation was dramatically enhanced in the presence of Li+ (1 mM), such that at 30 min it represented almost 35% of the total bisphosphate fraction. The accumulation of Ins(4,5)P2 appeared to be very sensitive to Li+ (EC50 = 94 +/- 3 microM), strongly implicating a Li(+)-sensitive metabolism. Evidence for this is provided from the rapid but Li(+)-sensitive decay of Ins(4,5)P2 when muscarinic-receptor stimulation is antagonized by atropine at a time when accumulations have reached a new steady state. Manipulation of phospholipase D by activators and inhibitors of protein kinase C did not suggest a role for phospholipase D hydrolysis of PtdInsP2 in the formation of Ins(4,5)P2. Attempts to reveal Ins(4,5)P2 metabolism, or indeed its synthesis from Ins(1,4,5)P3, were not successful with broken cell preparations and strongly suggest discrete compartmentation of inositol phosphate metabolism in the intact cell.

Noradrenaline-stimulated inositol phosphate accumulation in arteries from spontaneously-hypertensive rats

1. The effects of noradrenaline upon polyphosphoinositide (PPI) breakdown was investigated by measuring the accumulation of inositol phosphates (IPs) in tail arteries from normo- (WKY) and spontaneously-hypertensive (SHR) rats. 2. Noradrenaline (10(-7)-10(-3) M) evoked a concentration-dependent increase in total IP accumulation in both WKY and SHR rats but no significant differences between the populations were detected. 3. In contrast, significant differences in the accumulation of the individual IPs, which contributed to the total IP, occurred. A significantly greater noradrenaline-stimulated accumulation of inositol trisphosphate (IP3) was observed in tissues from SHR compared with those from WKY rats at each effective concentration of noradrenaline. This was paralleled by an equivalent reduction in inositol monophosphate (IP1) accumulation, consistent with the lack of a significant difference in noradrenaline-stimulated total IP accumulation between the two populations. 4. In time course studies, an enhanced noradrenaline-induced accumulation of IP3, in SHR compared to WKY rats, occurred from the earliest time point studied after the addition of the catecholamine both in the presence and absence of LiCL (10 mM). In the presence of LiCl (10 mM) no significant difference in noradrenaline-evoked total IP accumulation between SHR and WKY rats was observed; in the absence of LiCl noradrenaline-evoked a greater total IP accumulation in SHR than in WKY rats at all time points investigated. 5. These studies suggest that the main reason for the enhanced noradrenaline-induced accumulation of IP3 in arteries from SHR rats is a reduced rate of dephosphorylation of both IP3 and inositol bisphosphate (IP2) rather than a greater formation of IP3 from PPIs.6. This enhanced accumulation of IP3 may result in an increased calcium mobilisation accounting for the increased contractility to noradrenaline of tail arteries from SHR as compared with those from WKY rats.

Voluntary HIV testing in the antenatal clinic: differing uptake rates for individual counselling midwives

This study looked at 12 midwives in the Riverside Health Authority who counselled parturient women about having the HIV antibody test. Results showed that the uptake rate of the test varied considerably across midwives (82% to 3%). Uptake rate varied, to some extent, by ethnic group of the midwife; Afro-Caribbeans having 36% uptake, others 11%. However, the wide variation within these groups suggests that ethnicity alone does not explain the difference in uptake rate. Factors which could be associated with uptake rate are the individual characteristics of both the midwife and of the antenatal clinic attender, such as age, ethnicity, knowledge of and attitudes to HIV and antibody testing, as well as the counselling approach of the individual midwife.

Mucinous (adenocystic) sweat gland carcinoma of the great toe

The authors describe a rare case of mucinous (adenocystic) eccrine carcinoma isolated in the hallux and present a review of the literature. The potential for metastases involving this skin tumor is low with local excision and 1-year follow-up the treatment of choice.

Effects of valproate on hyponeophagia in rats: competitive antagonism with picrotoxin and non-competitive antagonism with RO 15-1788

The effects of valproate (30-500 mg/kg), alone and in combination with picrotoxin (1.5 mg/kg) or RO 15-1788 (10 mg/kg) were studied in two experiments on hyponeophagia in rats. Valproate reduced eating latency and increased eating time and amount eaten of novel food, except at 500 mg/kg which reduced feeding. Picrotoxin induced generally opposite actions alone and shifted valproate dose/response curves to the right. RO 15-1788 had no detectable intrinsic action, but prevented both the behavioural facilitation and inhibition produced by valproate. These findings are discussed in the context of the GABA hypothesis of benzodiazepine action, with the conclusions that they provide behavioural support for the hypothesis of a receptor complex with GABA and benzodiazepine binding sites, and that an optimal and submaximal level of activity at the benzodiazepine site is a necessary condition for anxiolytic actions of valproate.