Distinct chromatin structures at the monoamine oxidase-A promoter correlate with allele-specific expression in SH-SY5Y cells

Monoamine oxidase-A (MAOA) metabolises monoamines and is implicated in the pathophysiology of psychiatric disorders. A polymorphic repetitive DNA domain, termed the uVNTR (upstream variable number tandem repeat), located at the promoter of the MAOA gene is a risk factor for many of these disorders. MAOA is on the X chromosome suggesting gender could play a role in regulation. We analysed MAOA regulation in the human female cell line, SH-SY5Y, which is polymorphic for the uVNTR. This heterozygosity allowed us to correlate allele-specific gene expression with allele-specific transcription factor binding and epigenetic marks for MAOA. Gene regulation was analysed under basal conditions and in response to the mood stabiliser sodium valproate. Both alleles were transcriptionally active under basal growth conditions; however, the alleles showed distinct transcription factor binding and epigenetic marks at their respective promoters. Exposure of the cells to sodium valproate resulted in differential allelic expression which correlated with allele-specific changes in distinct transcription factor binding and epigenetic marks at the region encompassing the uVNTR. Biochemically our model for MAOA promoter function has implications for gender differences in gene × environment responses in which the uVNTR has been implicated as a genetic risk.

A TOMM40 poly-T variant modulates gene expression and is associated with vocabulary ability and decline in nonpathologic aging

The Translocase of Outer Mitochondrial Membrane 40 Homolog and Apolipoprotein E (TOMM40-APOE) locus has been associated with a number of age-related phenotypes in humans including nonpathologic cognitive aging, late-onset Alzheimer's disease, and longevity. Here, we investigate the influence of the TOMM40 intron 6 poly-T variant (rs10524523) on TOMM40 gene expression and cognitive abilities and decline in a cohort of 1613 community-dwelling elderly volunteers who had been followed for changes in cognitive functioning over a period of 14 years (range = 12-18 years). We showed that the shorter length poly-T variants were found to act as a repressor of luciferase gene expression in reporter gene constructs. Expression was reduced to approximately half of that observed for the very long variant. We further observed that the shorter poly-T variant was significantly associated with reduced vocabulary ability and a slower rate of vocabulary decline with age compared to the very long poly-T variants. No significant associations were observed for memory, fluid intelligence or processing speed, although the direction of effect, where the short variant was correlated with reduced ability and slower rate of decline was observed for all tests. Our results indicate that the poly-T variant has the ability to interact with transcription machinery and differentially modulate reporter gene expression and influence vocabulary ability and decline with age.

Allele-specific transcriptional activity of the variable number of tandem repeats in 5' region of the DRD4 gene is stimulus specific in human neuronal cells

The dopamine receptor D4 (DRD4) gene includes several variable number of tandem repeat loci that have been suggested to modulate DRD4 gene expression patterns. Previous studies showed differential basal activity of the two most common variants of a tandem repeat (120 bp per repeat unit) located in the 5' region adjacent to the DRD4 promoter in human cell lines. In this communication, we further characterized the ability of this polymorphic repeat to elicit tissue-, allele- and stimuli-specific transcriptional activity in vitro. The short and long variants of the DRD4 5' tandem repeat were cloned into a luciferase reporter gene construct containing the SV40 promoter. The luciferase constructs were cotransfected with expression vectors of two ubiquitously expressed human transcription factors (TFs), CCCTC-binding factor (CTCF) and upstream stimulatory factor 2 (USF2), into human cell lines and primary cultures of neonate rat cortex and luciferase activity measured. Overexpression with these TFs resulted in differential cell- and allele-specific transcriptional activities of the luciferase constructs. The results of our experiments show that variants of this tandem repeat in the 5' promoter of the DRD4 gene will direct differential reporter gene transcriptional activity in a cell-type-specific manner dependent on the signal pathways activated.

Variation in the composition of the AP1 complex in PC12 cells following induction by NGF and TPA

The rat pheochromocytoma cell line PC 12 differentiates in response to NGF. Exposure to NGF induces a class of genes termed immediate early that includes many transcription factors including c-jun and c-fos which can constitute the AP1 complex. Induction of such transcription factors by NGF could be a method by which the cell redirects its program of gene expression that results in differentiation. In this study, it is demonstrated that the complement of transcription factors that constitute the AP1 complex alters with the continued passage of PC12 cells. PC 12 cells from early passage contain no AP1 activity, whereas with passage the cells constitutively express an AP1 complex; however, no morphological differences are observed. The AP1 binding activity can be further induced in all PC12 cells studied by NGF or TPA. The analysis of c-jun, c-fos, and the fos-related antigens that can constitute the AP1 complex demonstrated compositional variation of this complex by passage in culture and by exposure to NGF or TPA. As these AP1 transcription complexes may mediate the action of NGF in PC12 cells it is important to correlate the changes in composition of the complex with differentiation.

Behavioural genetics of the serotonin transporter

The serotonin transporter is a key regulator of the bioavailability of serotonin and therefore any modulation in the expression or action of the transporter would be expected to have consequences on behaviour. The transporter has therefore become a target for pharmaceutical intervention in behavioural and mood disorders. The search for polymorphic variants in the transporter that would associate with neurological disorders has been extensive but has become focused on two domains which are both termed variable number tandem repeat (VNTR)polymorphisms. Both of these VNTRs are in non-coding DNA and therefore proposed to be mechanistically involved in a disorder through their ability to modulate transcriptional or post-transcriptional regulation of the transporter. The most extensively studied is in the promoter and is a bi-allelic insertion/deletion found in the 50 promoter region of the gene 1.2 kb upstream of the transcriptional start site. This VNTR, termed, 5-HTTLPR was initially identified as two variants containing either, 14 (short/deletion) or 16 (long/insertion) copies of a 22 bp repeat. A second widely studied VNTR found in the non-coding region of the transporter is located within intron 2 and comprises 9, 10 or 12 copies of a16–17 bp repeat termed, STin2.9, STin2.10 and STin2.12, respectively. These VNTR polymorphisms have been associated with a range of behavioural and psychiatric disorders including depression, OCD, anxiety and schizophrenia, however often the lack of reproducibility in different cohorts has led to debate on the actual association of the polymorphisms with this extensive range of neurological conditions. Here we review these two polymorphic VNTRs in depth and relate that to pharmaceutical response, their ability to regulate differential transporter expression, their core involvement in gene-environment interaction and their genetic association with specific disorders.

Phosphonoacetate biosynthesis: in vitro detection of a novel NADP(+)-dependent phosphonoacetaldehyde-oxidizing activity in cell-extracts of the marine Roseovarius nubinhibens ISM

A novel phosphonoacetaldehyde-oxidizing activity was detected in cell-extracts of the marine bacterium Roseovarius nubinhibens ISM grown on 2-aminoethylphosphonic acid (2-AEP; ciliatine). Extracts also contained 2-AEP transaminase and phosphonoacetate hydrolase activities. These findings indicate the existence of a biological route from 2-AEP via phosphonoacetaldehyde for the production of phosphonoacetate, which has not previously been shown to be a natural product. The three enzymes appear to constitute a previously-unreported pathway for the mineralization of 2-AEP which is a potentially important source of phosphorus in the nutrient-stressed marine environment.

Intercontinental spread from Israel to Colombia of a KPC-3-producing Klebsiella pneumoniae strain

In 2008, an increase in the prevalence of carbapenem-resistant Klebsiella pneumoniae was noted in a 286-bed tertiary case hospital in Colombia, where 84 patients (32 infected and 52 colonized) had positive cultures. The identified index patient came from Israel for a liver transplantation. High level carbapenem resistance was observed. Polymyxin B and tigecycline were the only two antibiotics that remained active. PCR-restriction fragment length polymorphism analysis and sequencing revealed blaKPC-3 in the major clone, which was indistinguishable from the K. pneumoniae carbapenemase-3-producing clone described previously in Israel. This exemplifies the threat posed by the global spread of K. pneumoniae carbapenemase-producing pathogens.

Stimulation of phosphate uptake and polyphosphate accumulation by activated sludge microorganisms in response to sulfite addition

Enhanced phosphate removal from wastewaters is dependent on the synthesis and intracellular accumulation of polyphosphate by sludge microorganisms. However the role played by polyphosphate in microbial metabolism and the factors that trigger its formation remain poorly-understood. Many examples of the accumulation of the biopolymer by environmental microorganisms are documented; these include a recent report of the presence of large polyphosphate inclusions in sulfur-oxidizing marine bacteria. To investigate whether any link might exist outside the marine environment between the presence of reduced sulfur compounds and enhanced levels of microbial phosphate uptake and polyphosphate accumulation, activated sludge cultures were grown under laboratory conditions in media that contained sulfite, thiosulfate, hydrosulfite or tetrathionate. Only in the presence of sulfite was there any evidence of a stimulatory effect; in medium that contained 0.5 mM sodium sulfite some 17% more phosphate was removed by the sludge, whilst there was an almost two-fold increase in intracellular polyphosphate levels. No indications of sulfite toxicity were observed.

Abstract P2-06-03: A Polymorphic AAAG Repeat in the Estrogen Receptor-Related-Gamma Gene May Represent a Breast Cancer Predisposition Biomarker

Background: There is a strong genetic component to breast cancer, which is the most common neoplasm in women; however current risk markers are few, accounting for less than 10% of breast cancer cases. This means that the majority of familial breast cancers remain unexplained. Our laboratory has studied microsatellite polymorphisms for many years, and we developed techniques to assay these understudied regions of the genome en masse and individually via shot-gun methods to rapidly identify those that are likely to be polymorphic and therefore potentially contribute to phenotype.

Material and Methods: Using these novel approaches, we identified a polymorphic AAAG microsatellite repeat in the estrogen-related receptor gamma (ERR-γ) that is expanded in -10% of the general population. We genotyped over 300 individuals and found a longer allelic version (13+ repeat copies) in 14.3% of breast cancer patients, compared to only 4.8% in cancer-free individuals. We computationally identified 22 transcription factors that could bind directly to this AAAG repeat and the surrounding region. We hypothesized that the AAAG-containing region might serve as a promoter for ERR-y.

Results: We found a statistically significant number of breast cancer patients with the expanded AAAG allele, and preliminary experiments confirm that the AAAG-containing region of ERR-γ does indeed drive reporter gene expression in estrogen receptor positive (ER+) MCF-7 breast cancer cells. This was not the case for the ER-breast cancer cells (MDA-MB-231) we also examined. Our initial assessments also revealed that SKBR-3 breast cancer cells are naturally heterozygotic for the long and short allelic versions of the AAAG repeat. Our ongoing studies involve knockdown of transcription factors in MCF-7 cells that abrogate the endogenous expression of ERR-γ.

Discussion: The role of microsatellites in cancer is well defined for colon cancer, but few studies have been conducted to examine the contribution of these simple sequence repeats in breast cancer. We discovered a polymorphic AAAG repeat in the ERR-γ gene, and our studies indicate that a longer version of this repeat is more prevalent in the genomes of breast cancer patients. Based on our assessment, this allele carries a 2.98 relative risk for the development of breast cancer. The higher incidence of this putative biomarker in breast cancer patients may be a result of altered ERR-γ expression, as the AAAG-containing sequence can drive reporter expression. If the frequency of this potentially predictive marker is sustained in a larger population, and the mechanism by which it confers the cancer phenotype can be identified, it may contribute substantially as a biomarker offering surveillance, prophylactic surgery, and chemoprevention options to patients.

Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr P2-06-03.

A long AAAG repeat allele in the 5' UTR of the ERR-γ gene is correlated with breast cancer predisposition and drives promoter activity in MCF-7 breast cancer cells

We sequenced the 5' UTR of the estrogen-related receptor gamma gene (ERR-γ) in ~500 patient and volunteer samples and found that longer alleles of the (AAAG)(n) microsatellite were statistically and significantly more likely to exist in the germlines of breast cancer patients when compared to healthy volunteers. This microsatellite region contains multiple binding sites for a number of transcription factors, and we hypothesized that the polymorphic AAAG-containing sequence in the 5' UTR region of ERR-γ might modulate expression of ERR-γ. We found that the 369 bp PCR product containing the AAAG repeat drove expression of a reporter gene in estrogen receptor positive breast cancer cells. Our results support a role for the 5' UTR region in ERR-γ expression, which is potentially mediated via binding to the variable tandem AAAG repeat, the length of which correlates with breast cancer pre-disposition. Our study indicates that the AAAG tetranucleotide repeat polymorphism in ERR-γ gene 5' UTR region may be a new biomarker for genetic susceptibility to breast cancer.

Evidence for phosphonate usage in the coral holobiont

Phosphonates are characterized by a stable carbon-phosphorus bond and commonly occur as lipid conjugates in invertebrate cell membranes. Phosphonoacetate hydrolase encoded by the phnA gene, catalyses the cleavage of phosphonoacetate to acetate and phosphate. In this study, we demonstrate the unusually high phnA diversity in coral-associated bacteria. The holobiont of eight coral species tested positive when screened for phnA using degenerate primers. In two soft coral species, Sinularia and Discosoma, sequencing of the phnA gene showed 13 distinct groups on the basis of 90% sequence identity across 100% of the sequence. A total of 16 bacterial taxa capable of using phosphonoacetate as the sole carbon and phosphorus source were isolated; 8 of which had a phnA+ genotype. This study enhances our understanding of the wide taxonomic and environmental distribution of phnA, and highlights the importance of phosphonates in marine ecosystems.

The human neurokinin B gene, TAC3, and its promoter are regulated by Neuron Restrictive Silencing Factor (NRSF) transcription factor family

We have previously shown that one of the major determinants directing the expression of the preprotachykinin-A (TAC1) gene, which encodes the neuropeptide substance P, is the transcription factor Neuronal Restrictive Silencer Factor (NSRF), which is also termed Repressor Element-1 Silencing Factor (REST). In rodent models of epilepsy, NRSF and its truncated isoform short NRSF (sNRSF), also termed REST4, are increased as an immediate response to seizure. In similar models the neurokinin B (NKB) gene (TAC3) is also induced and NKB has also been shown to be proconvulsant. In this communication we have demonstrated that both the TAC3 endogenous gene and its promoter are regulated, directly or indirectly, by the NRSF transcription factors resulting in both the increased expression of the endogenous gene and increased reporter gene activity. We demonstrate by chromatin immunoprecipitation analysis that NRSF and sNRSF will bind to the NKB promoter in vivo. Consistent with a model in which NRSF modulation of TAC3 gene expression is a mechanism that operates during epilepsy, the observed increases in both the level of the endogenous gene and the activity of the NKB promoter by these NRSF variants, were diminished by the action of the anticonvulsant drug, carbamazepine.

New developments in carbapenems

Antibiotic resistance among Gram-negative pathogens in hospitals is a growing threat to patients and is driving the increased use of carbapenems. Carbapenems are potent members of the beta-lactam family of antibiotics, with a history of safety and efficacy for serious infections that exceeds 20 years. Original and review articles were identified from a Medline search (1979-2008). Reference citations from identified publications, abstracts from the Interscience Conferences on Antimicrobial Agents and Chemotherapy and package inserts were also used. Carbapenems are effective in treating severe infections at diverse sites, with relatively low resistance rates and a favourable safety profile. Carbapenems are the beta-lactams of choice for the treatment of infections caused by multidrug-resistant organisms. Optimized dosing of carbapenems should limit the emergence of resistance and prolong the utility of these agents. The newly approved doripenem should prove to be a valuable addition to the currently available carbapenems: imipenem, meropenem and ertapenem.

Mechanical stimulation induces preprotachykinin gene expression in osteoarthritic chondrocytes which is correlated with modulation of the transcription factor neuron restrictive silence factor

We have previously demonstrated that the transcription factor termed neuron restrictive silencer factor (NRSF) and the truncated splice variant, NRSF short form (sNRSF) are major modulators of preprotachykinin A (TAC1) gene expression. In this communication we addressed whether TAC1 gene expression would be effected in response to mechanical stimulation of both normal and osteoarthritic (OA) chondrocytes. Chondrocytes were mechanically stimulated for 20 min, and then incubated under normal tissue culture conditions for 1 or 3h. RT-PCR and quantitative PCR (qPCR) were used to investigate expression of TAC1, NRSF and sNRSF mRNA at these time points. Western blotting was used to validate and confirm expression of sNRSF protein in chondrocytes in response to mechanical stimulation. We observed that TAC1 was expressed in normal chondrocytes, with no evidence of NRSF or sNRSF expression. TAC1 mRNA expression did not significantly change following mechanical stimulation in normal cells. OA chondrocytes expressed TAC1 and sNRSF mRNA, though not NRSF, and following mechanical stimulation there was a significant upregulation of both TAC1 and sNRSF mRNA, which returned to baseline levels 3h post-stimulation. sNRSF protein was upregulated at 1 and 2h following stimulation of OA chondrocytes. In summary, differential expression of TAC1 and sNRSF in OA chondrocytes associates their expression with the disease. The change in expression of sNRSF and TAC1 mRNA following mechanical stimulation in OA but not normal chondrocytes suggests that sNRSF may be involved in the regulation of SP production in OA cartilage. These differences between normal and OA mechanotransduction responses may be important in the production of phenotypic changes present in diseased cartilage.

Additive effect of BDNF and REST polymorphisms is associated with improved general cognitive ability

Brain-derived neurotrophic factor (BDNF) is a pleiotropic protein involved in neuronal proliferation, differentiation, synaptic plasticity and survival. Independent studies investigating association between the functional BDNF Val66Met polymorphism and cognitive abilities have reported some conflicting findings, which may reflect inadequate sample size, variation in testing methods, population stratification or the confounding effects of other genes. To test the latter hypothesis, we screened and genotyped polymorphisms in the RE1-silencing transcription factor (REST) gene whose function includes the downregulation of BDNF expression. We identified an exon 4 hexadecapeptide variable number tandem repeat (VNTR) with either four or five copies that was located within a proline-rich domain and investigated a further five single nucleotide polymorphisms (SNPs). Using a cohort of 746 community-dwelling older volunteers, we analysed REST genotype data both independently and in combination with the BDNF Val66Met polymorphism. A haplotype within the REST gene containing the four copy VNTR and a non-synonymous SNP showed a weak but significant association with a higher score of general intelligence (P = 0.05). Analysis of this haplotype and the BDNF Val66Met polymorphism in combination showed a significant interaction (global P-value = 0.0003) with an additive increase in cognitive performance for those possessing the BDNF Val66 allele and the REST haplotype containing the four copy repeat (P = 0.004). The REST haplotypes in combination with the BDNF Met66 polymorphism did not reduce cognitive performance more than the independent influence of the Met66 allele. Our results suggest that investigation of a common REST polymorphism may be necessary to help reduce contrasting reports based around BDNF Val66Met and cognition.

Expression of activity-dependent neuroprotective protein in the brain of adult rats

Activity-dependent neuroprotective protein (ADNP) is a VIP-regulated gene, which is essential for brain development. A synthetic peptide (NAP) derived from the ADNP sequence is highly neuroprotective, therefore it has been hypothesised that ADNP has a similar role. ADNP contains classical transcription factor motifs and nuclear localisation domains, but it has also been reported to be secreted and to co-localise with microtubules, indicating that ADNP may have multiple functions. We investigated the pattern of ADNP expression by immunohistology in normal rat brain, in order to generate a framework for future studies examining changes in ADNP expression in response to noxious stimuli or in models of disease. We found widespread ADNP-like immunoreactivity in neurons throughout the rat brain, with the highest expression in the cerebellum, and strong expression in the thalamus, mesencephalon, pons and medulla oblongata. ADNP-like immunoreactivity was mainly observed in the cytoplasm of neurons, and fibre tracts were often strongly positive as well. In addition, positive neuronal nuclei were occasionally observed. ADNP-like immunoreactivity was lost in degenerating "dark" neurons, whereas it appeared to locate to the nucleus in some of the morphologically unaltered adjacent cells. Occasional astrocyte and microglial cells were also positive. We suggest that the widespread expression of ADNP may correlate with the wide-ranging protective effects of NAP, and that the cytoplasmic and axonal localisation of ADNP-like immunoreactivity suggests additional, non-transcriptional functions of ADNP.

Molecular genetics of monoamine transporters: relevance to brain disorders

We have demonstrated in both the human serotonin transporter gene (5HTT) and the dopamine transporter gene (DAT1) that specific polymorphic variants termed Variable Number Tandem Repeats (VNTRs), which correlate with predisposition to a number of neurological and psychiatric disorders, act as transcriptional regulatory domains. We have demonstrated that these domains can act as both tissue-specific and stimulus-inducible regulators of gene expression. As such they can act to be mechanistically associated with the progression or initiation of a behavioural disorder by altering the level of transporter mRNA, which in turn regulates the concentration of transporter in specific cells or in response to a challenge; chemical, environmental or physiological. The synergistic actions of such transcriptional domains will modulate gene expression. Our hypothesis is that these VNTR variants are one mechanism by which nurture can modify concentrations of neurotransmitters in a differential manner.

Generation of a transgenic model to address regulation and function of the human neurokinin 1 receptor (NK1R)

We have generated mouse transgenic lines using yeast artificial chromosome (YAC) technology which demonstrate expression from the human NK1 receptor (NK1R) locus. We introduced a 380 kb fragment encompassing the human NK1R gene and flanking regions which we hoped would recapitulate the expected endogenous expression of the human gene. To visualise this expression the NK1 locus co-expresses the green fluorescence protein gene (GFP) under the control of an internal ribosome entry site (IRES) sequence. We have generated five mouse lines that express the human NK1 receptor gene with and without the marker gene. All the lines incorporating the marker gene appear to exhibit the same expression pattern in analysis of selected anatomical regions throughout the mouse. The lack of a human specific NK1R antibody determined that we could not distinguish between expression of the transgene and endogenous NK1R. Our analysis has shown transgene expression in brain areas known to express NK1R in human such as the hippocampus and caudate putamen. The majority of these cells were also positive for GFP fluorescence. These transgenic lines may prove a good pre-clinical model as drugs can be addressed against both the human receptor and modulators of its expression in vivo.

Prevalence of AmpC over-expression in bloodstream isolates of Pseudomonas aeruginosa

This study examined the contribution of AmpC over-expression to beta-lactam resistance in clinical isolates of Pseudomonas aeruginosa obtained from a hospital in Houston, TX, USA. Seventy-six non-repeat bloodstream isolates obtained during 2003 were screened for ceftazidime resistance in the presence and absence of clavulanic acid 4 mg/L. AmpC was identified by isoelectric focusing (with and without cloxacillin inhibition); stable derepression was ascertained phenotypically by a spectrophotometric assay (with and without preceding induction by imipenem) using nitrocefin as the substrate, and was confirmed subsequently by quantitative RT-PCR of the ampC gene. The clonal relatedness of the AmpC-over-expressing isolates was assessed by pulsed-field gel electrophoresis. In addition, the ampC and ampR gene sequences were determined by PCR and sequencing. For comparison, two standard wild-type strains (PAO1 and ATCC 27853) and three multidrug-susceptible isolates were used as controls. AmpC over-expression was confirmed in 14 ceftazidime-resistant isolates (overall prevalence rate, 18.4%), belonging to seven distinct clones. The most prevalent point mutations in ampC were G27D, V205L and G391A. Point mutations in ampR were also detected in eight ceftazidime-resistant isolates. AmpC over-expression appears to be a significant mechanism of beta-lactam resistance in P. aeruginosa. Understanding the prevalence and mechanisms of beta-lactam resistance in P. aeruginosa may guide the choice of empirical therapy for nosocomial infections in hospitals.

Regulation and role of REST and REST4 variants in modulation of gene expression in in vivo and in vitro in epilepsy models

Repressor element-1 silencing transcription factor (REST) is a candidate modulator of gene expression during status epilepticus in the rodent. In such models, full-length REST and the truncated REST4 variant are induced and can potentially direct differential gene expression patterns. We have addressed the regulation of these REST variants in rodent hippocampal seizure models and correlated this with expression of the proconvulsant, substance P encoding, PPT-A gene. REST and REST4 were differentially regulated following kainic acid stimulus both in in vitro and in vivo models. REST4 was more tightly regulated than REST in both models and its transient expression correlated with that of the differential regulation of PPT-A. Consistent with this, overexpression of a truncated REST protein (HZ4, lacking the C-terminal repression domain) increased expression of the endogenous PPT-A gene. Similarly the proximal PPT-A promoter reporter gene construct was differentially regulated by the distinct REST isoforms in hippocampal cells with HZ4 being the major inducer of increased reporter expression. Furthermore, REST and REST4 proteins were differentially expressed and compartmentalized within rat hippocampal cells in vitro following noxious stimuli. This differential localization of the REST isoforms was confirmed in the CA1 region following perforant path and kainic acid induction of status epilepticus in vivo. We propose that the interplay between REST and REST4 alter the expression of proconvulsant genes, as exemplified by the PPT-A gene, and may therefore regulate the progression of epileptogenesis.

Effect of reduced pH on inorganic polyphosphate accumulation by Burkholderia cepacia complex isolates

AIMS

Burkholderia cepacia complex (Bcc) isolates causing pulmonary infection in cystic fibrosis (CF) patients grow within an acidic environment in the lung. As exposure to acid pH has been shown to increase intracellular inorganic polyphosphate (polyP) formation in some bacteria, we investigated the inter-relationship between acidic pH and polyP accumulation in Bcc isolates.

METHODS AND RESULTS

The formation of polyP by one Burkholderia cenocepacia clinical isolate was initially examined at a range of pH values by measuring total intracellular polyP accumulation and phosphate uptake. The pattern of polyP accumulation corresponded with the pattern of phosphate uptake with the maximum for both occurring at pH 5.5. Phosphate uptake and formation of polyP by this isolate was further determined over 48 h at pH 5.5, 6.5 and 7.5; formation of polyP was maximal at pH 5.5 at all time points studied. Sixteen of 17 additional clinical and environmental Bcc isolates examined also exhibited maximum phosphate uptake at pH 5.5.

CONCLUSIONS

Both clinical and environmental Bcc isolates, of five genomovars, show enhanced formation of polyP in an acidic environment. Given both the speculated role of polyP in pathogenesis, cell signalling and biofilm formation and the acidic nature of the CF lung, this may be of considerable clinical importance.

SIGNIFICANCE AND IMPACT OF THE STUDY

Growth of Bcc in an acidic environment, such as that found in the lungs of CF patients may be influenced in part by polyP accumulation.

Myelodysplastic patients with raised percentage of hypochromic red cells have evidence of functional iron deficiency

Raised percentage hypochromic red cells (%HRC) were detected at diagnosis in 10 of 34 consecutive patients with low-risk myelodysplastic syndrome (MDS) [refractory anemia (RA) (4/26) and RA with ring sideroblasts (6/8)], all of whom had normal or increased serum ferritin and bone marrow iron stores. Elevated %HRC has persisted in all 10 cases and subsequently developed in another RA patient who later had a complete remission of MDS with normalisation of %HRC after a respiratory tract infection. A strong positive correlation was found between %HRC and erythrocyte zinc protoporphyrin levels in 11 MDS patients tested (p=0.01), suggesting that functional iron deficiency contributes to ineffective erythropoiesis in cases of MDS with raised %HRC. Five of seven patients with elevated %HRC had satisfactory haemoglobin responses to a trial of human recombinant erythropoietin without iron supplementation.

Nitric oxide, a biological double-faced janus--is this good or bad?

Nitric oxide (NO) is a biological messenger molecule produced by one of the essential amino acids L-arginine by the catalytic action of the enzyme NO synthase (NOS). The dual role of NO as a protective or toxic molecule is due to several factors, such as; the isoform of NOS involved, concentration of NO and the type of cells in which it is synthesised, the availability of the substrate L-arginine, generation of guanosine 3,5'-cyclic monophosphate (cGMP) from soluble guanylate cyclase and the overall extra and intracellular environment in which NO is produced. NOS activation as a result of trauma (calcium influx) or infection leads to NO production, which activates its downstream receptor sGC to synthesise cGMP and/or leads to protein nitrosylation. This may lead to one or more systemic effects including altered neurotransmission which can be protective or toxic, vaso/bronchodilatation in the cardiovascular and respiratory systems and enhanced immune activity against invading pathogens. In addition to these major functions, NO plays important role in thermoregulation, renal function, gastrointestinal motility, endocrine function, and various functions of the urogenital system ranging from renin secretion to micturation; spermatogenesis to penile erection; and ovulation to implantation and parturition. A schematic summary of the functions of NO and the various isoforms of NOS expressed in body systems is shown in figure 1. In this review, the historical background, biochemistry and biosynthesis of NO and its enzymes together with the mechanism of NO actions in physiology and pathophysiology are discussed.

Development of Daptomycin resistance in vivo in methicillin-resistant Staphylococcus aureus

Daptomycin is a new lipopeptide antibiotic that is rapidly bactericidal against Staphylococcus aureus. We report daptomycin resistance and treatment failure in 2 patients with osteomyelitis due to methicillin-resistant S. aureus. Disk diffusion susceptibility testing failed to detect resistance. Daptomycin at high concentration retained bactericidal activity against resistant isolates.

Problem pulmonary pathogens: Pseudomonas aeruinosa

Pseudomonas aeruginosa is a common and highly lethal agent of nosocomial pneumonia, especially among patients receiving mechanical ventilation. It is widespread in the environment and commonly recovered from water in nature and in hospital settings. P. aeruginosa is endowed with a formidable array of virulence factors that facilitate attachment to host cells, tissue invasion, and systemic disease. It is intrinsically resistant to many commonly used antibiotics due to a complex variety of mechanisms that we will briefly review. Recent advances in the understanding of the molecular biology of this organism have shed considerable light on its ability to form biofilms, which facilitate adherence especially in cystic fibrosis patients, and confer resistance to clearance by host immune mechanisms and antimicrobial killing. Treatment studies have demonstrated a significant risk of emergence of resistance during therapy with a variety of agents. Several studies suggest that two drugs are better than one for therapy of serious infections, although dual therapy does not always prevent emergence of resistant strains.

Bowel colonization with resistant gram-negative bacilli after antimicrobial therapy of intra-abdominal infections: observations from two randomized comparative clinical trials of ertapenem therapy

The selection of resistant gram-negative bacilli by broad-spectrum antibiotic use is a major issue in infection control. The aim of this comparative study was to assess the impact of different antimicrobial regimens commonly used to treat intra-abdominal infections on the susceptibility patterns of gram-negative bowel flora after completion of therapy. In two international randomized open-label trials with laboratory blinding, adults with complicated intra-abdominal infection requiring surgery received piperacillin-tazobactam (OASIS 1) or ceftriaxone/metronidazole (OASIS II) versus ertapenem for 4-14 days. Rectal swabs were obtained at baseline, end of therapy, and 2 weeks post-therapy. Escherichia coli and Klebsiella spp. were tested for production of extended-spectrum beta-lactamase (ESBL). Enterobacteriaceae resistant to the agent used were recovered from 19 of 156 (12.2%) piperacillin-tazobactam recipients at the end of therapy compared to 1 (0.6%) patient at baseline (p<0.001) in OASIS I, and from 33 of 193 (17.1%) ceftriaxone/metronidazole recipients at the end of therapy compared to 5 (2.6%) patients at baseline (p<0.001) in OASIS II. Ertapenem-resistant Enterobacteriaceae were recovered from 1 of 155 and 1 of 196 ertapenem recipients at the end of therapy versus 0 and 1 ertapenem recipients at baseline in OASIS I and II, respectively. Resistant Enterobacteriaceae emerged significantly less often during treatment with ertapenem than with the comparator in both OASIS I (p<0.001) and OASIS II (p<0.001). The prevalence of ESBL-producers increased significantly during therapy in OASIS II among 193 ceftriaxone/metronidazole recipients (from 4 [2.1%] to 18 [9.3%]) (p<0.001), whereas no ertapenem recipient was colonized with an ESBL-producer at the end of therapy in either study. Selection for imipenem-resistant Pseudomonas aeruginosa was uncommon in all treatment groups. In these studies, the frequency of bowel colonization with resistant Enterobacteriaceae substantially increased in patients treated with either piperacillin-tazobactam or ceftriaxone/metronidazole, but not in patients treated with ertapenem.

First nosocomial outbreak of Pseudomonas aeruginosa producing an integron-borne metallo-beta-lactamase (VIM-2) in the United States

Carbapenemases are rare in the United States. This is the first report of a United States nosocomial outbreak of pan-resistant Pseudomonas aeruginosa infections due to an integron-borne metallo-beta-lactamase, VIM-2. This emergence of carbapenemases on mobile genetic elements in the United States warrants surveillance.

An evaluation of three new-generation tetrazolium salts for the measurement of respiratory activity in activated sludge microorganisms

XTT (3'-[1-[(phenylamino)-carbonyl]-3,4-tetrazolium]-bis(4-methoxy-6-nitro)benzenesulfonic acid hydrate), MTS (3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium, inner salt), and WST-1 (4-(3-4-iodophenyl)-2-(4-nitrophenyl)-2H-5-tetrazolio)-1,3-benzenedisulfonate) are tetrazolium salts that have become commercially available only in relatively recent years; they differ from earlier such compounds in that their reduction gives rise to a formazan product that is water soluble. We have established the sites in the prokaryotic respiratory chain at which each of the dyes is reduced to its corresponding formazan and have evaluated the suitability of each for the colorimetric estimation of electron transport system activity in populations of activated sludge microorganisms. Reduction of all three tetrazolium salts was shown to be proportional to cell biomass and oxygen uptake and to be susceptible to low levels of the reference toxicant 3,5-dichlorophenol. XTT, which was not inhibitory at concentrations of up to 2 mM and was reduced by 91% of isolates from a sample of culturable activated sludge bacteria, was chosen for further assay development. XTT-formazan production was found to be stimulated by the availability of an exogenous carbon and energy source, and by the presence of the electron-coupling agent phenazine methosulfate. Less than 3% of XTT reduction by an activated sludge sample was abiotic. An assay based on this compound could be a valuable and simple tool for the routine monitoring of the performance of wastewater treatment systems.

The serotonin transporter intronic VNTR enhancer correlated with a predisposition to affective disorders has distinct regulatory elements within the domain based on the primary DNA sequence of the repeat unit

We have demonstrated that a variable number tandem repeat domain (VNTR) within intron 2 of the serotonin transporter gene is a transcriptional regulatory domain which is potentially correlated with a predisposition to affective disorders and other behavioural conditions. This correlation based on copy number of the VNTR alone (nine, 10 or 12 copies of 16/17 base-pair element) has been controversial and not reproduced in all studies. We demonstrate that individual repeat elements within the VNTR domain differ in their enhancer activity in an embryonic stem cell model. This has implications for both the mechanism by which these VNTRs are correlated with the progression of the disease and suggests that clinical analysis should now be extended to correlate sequence variation within the VNTR with the disorder. The latter may resolve some of the conflicting data published to date.

Tachykinin expression in cartilage and function in human articular chondrocyte mechanotransduction

OBJECTIVE

To assess whether substance P and the corresponding neurokinin 1 (NK1) receptor are expressed in human articular cartilage, and whether these molecules have a role in chondrocyte mechanotransduction.

METHODS

Transgenic studies, immunohistochemistry, Western blotting, and reverse transcriptase-polymerase chain reaction were used to assess the expression of the preprotachykinin (PPT) gene, substance P, and NK1 in developing mice, in adult human articular cartilage, and in human chondrocytes in culture. Chondrocytes obtained from PPT knockout mice and human articular chondrocytes were mechanically stimulated in the presence or absence of inhibitors of substance P signaling, and cell membrane potentials or relative levels of aggrecan messenger RNA (mRNA) were measured.

RESULTS

Replacing a region of the PPT gene transcriptional site that contains a dominant repressor of the proximal promoter activity with the constitutive minimal promoter of the human beta-globin promoter allowed expression of a marker gene in areas of chondrogenesis during mouse development and in adult chondrocytes grown in culture. Adult human articular chondrocytes expressed endogenous PPT mRNA, substance P, and the corresponding NK1 receptor in vivo and in vitro. Blockade of substance P signaling by a chemical antagonist to the NK1 receptor inhibited chondrocyte responses to mechanical stimulation.

CONCLUSION

Substance P is expressed in human articular cartilage and is involved in chondrocyte mechanotransduction via the NK1 receptor in an autocrine and paracrine manner. This suggests that substance P and the NK1 receptor have roles in the maintenance of articular cartilage structure and function that were previously unrecognized.

Neuron restrictive silencer factor as a modulator of neuropeptide gene expression

We hypothesize that the transcription factor neuron restrictive silencer factor (NRSF) is an important determinant of the expression of the preprotachykinin (PPTA) gene (encoding substance P and Neurokinin A) and arginine vasopressin (AVP) both in neuronal and nonneuronal cells. NRSF, a zinc finger repressor protein, binds the NRSE motif found in many neuronal specific genes at a variety of promoter locations. However, it is found in a similar location at the major transcriptional start site, within both PPTA and AVP peptide promoters. We have correlated modulation of NRSF activity with expression of AVP and PPTA in a variety of cell types, indicating the general mechanism by which this protein may regulate expression. Specifically, they are as follows:(1). Expression of NRSF dramatically represses PPTA promoter activity in reporter gene constructs in primary cultures of DRG neurons.(2). The PPTA promoter activity is regulated differentially in osteoarthritic compared to normal chondrocytes. This regulation correlates with the region containing the NRSE site.(3). We have correlated a splice variant of NRSF with the establishment and progression of small cell lung carcinoma (SCLC) and demonstrated that NRSF variants can directly affect the activity of the AVP promoter in reporter gene constructs. If the deregulated expression of peptides in these diseases point to the mechanism determining the pathology, then perhaps targeting protocols that correct this deregulation may also reverse the specific disease phenotypes. Our data would indicate that modulation of NRSF activity would be a target for such intervention.

Broad resistance due to plasmid-mediated AmpC beta-lactamases in clinical isolates of Escherichia coli

Escherichia coli that produce plasmid-mediated AmpC beta-lactamases are rare in the United States. The clinical features associated with infection with these organisms have not been well described. We identified 2 clinical isolates of E. coli that produced the plasmid-mediated AmpC enzyme beta-lactamase CMY-2. These organisms were recovered from urine specimens and were resistant to ceftazidime, ceftriaxone, and cefepime. One isolate was resistant to ertapenem but susceptible to imipenem and meropenem; the other was susceptible to imipenem, meropenem, and ertapenem. One of the 2 infected patients did not require specific therapy; the other required imipenem for cure. The presence of the CMY-2 beta-lactamase was confirmed by DNA sequencing. Hybridization studies confirmed that the bla(CMY-2) gene was on a plasmid in both isolates; in one of them, the probe also hybridized with chromosomal DNA. Infection with plasmid-mediated AmpC beta-lactamases in E. coli in the United States may be associated with treatment failure, and these strains may become a serious nosocomial threat.

Enhanced phosphate uptake and polyphosphate accumulation in Burkholderia cepacia grown under low pH conditions

Of bacterial cells in a sample of activated sludge, 34% contained detectable intracellular polyphosphate inclusions following Neisser staining, when grown on glucose/mineral salts medium at pH 5.5; at pH 7.5 only 7% of cells visibly accumulated polyphosphate. In a sludge isolate of Burkholderia cepacia chosen for further study, maximal removal of phosphate and accumulation of polyphosphate occurred at pH 5.5; levels were up to 220% and 330% higher, respectively, than in cells grown at pH 7.5. During the early stationary phase of growth at pH 5.5 a maximum level of intracellular polyphosphate that comprised 13.6% of cellular dry weight was reached. Polyphosphate kinase activity was detected in actively growing cells only when cultured at pH 5.5. The phenomenon of acid-stimulated phosphate uptake and polyphosphate accumulation in this environmental bacterial population parallels observations previously made by us in the yeast Candida humicola and may thus represent a widespread microbial response to low external pH values.

The dopamine transporter gene (SLC6A3) variable number of tandem repeats domain enhances transcription in dopamine neurons

The dopamine (DAT) and serotonin (SERT) transporter genes both contain variable number of tandem repeats (VNTR) in non-coding gene regions which have been correlated with a predisposition to a variety of CNS disorders. There is considerable homology between individual DAT and SERT repeat DNA sequences, which is reflected in their ability to compete with each other for specific protein binding as demonstrated by electrophoretic mobility shift assay. The SERT VNTR has recently been shown to act as a transcriptional enhancer. Because of the similarities between SERT and DAT VNTRs, the DAT VNTR may also enhance transcription. This study demonstrates by lipid transfection into an immortalized dopaminergic cell line and biolistic transfection into dopamine neurons in neonatal rat midbrain slices that the human nine-repeat DAT VNTR can enhance transcription. This enhancing activity suggests that the DAT VNTR may play a role in regulation of DAT gene expression.