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Brian J Morris

Publications and source records attributed to Brian J Morris.

At least 37 records · Page 2Linked to original sources
PubMed2005

Genomic profiling of the neuronal target genes of the plasticity-related transcription factor -- Zif268.

The later phases of neuronal plasticity are invariably dependent on gene transcription. Induction of the transcription factor Zif268 (Egr-1) in neurones is closely associated with many forms of functional plasticity, yet the neuronal target genes modulated by Zif268 have not been characterized. After transfection of a neuronal cell line with Zif268 we identified genes that show altered expression using high density microarrays. Although some of the genes identified have previously been associated with forms of neuronal plasticity, the majority have not been linked with neuronal plasticity or Zif268 action. Altered expression of a representative sample of the novel target genes was confirmed in Zif268-transfected PC12 neurones, and in in vitro and in vivo models of Zif268-associated neuronal plasticity. In particular, altered expression of the protease inhibitor Cystatin C and the chemokine Cxcl10 was observed in striatal tissue after haloperidol administration. Surprisingly, the group of identified genes is enriched for components of the proteasome and the major histocompatibility complex. Our findings suggest that altered expression of these genes following Zif268 induction may be a key component of long lasting plasticity in the CNS.

Animals↗
PubMed2005

BRCTx is a novel, highly conserved RAD18-interacting protein.

The BRCT domain is a highly conserved module found in many proteins that participate in DNA damage checkpoint regulation, DNA repair, and cell cycle control. Here we describe the cloning, characterization, and targeted mutagenesis of Brctx, a novel gene with a BRCT motif. Brctx was found to be expressed ubiquitously in adult tissues and during development, with the highest levels found in testis. Brctx-deficient mice develop normally, show no pathological abnormalities, and are fertile. BRCTx binds to the C terminus of hRAD18 in yeast two-hybrid and immunoprecipitation assays and colocalizes with this protein in the nucleus. Despite this, Brctx-deficient murine embryonic fibroblasts (MEFs) do not show overt sensitivity to DNA-damaging agents. MEFs from Brctx-deficient embryos grow at a similar rate to wild-type MEF CD4/CD8 expressions, and the cell cycle parameters of thymocytes from wild-type and Brctx knockout animals are indistinguishable. Intriguingly, the BRCT domain of BRCTx is responsible for mediating its localization to the nucleus and centrosome in interphase cells. We conclude that, although highly conserved, Brctx is not essential for the above-mentioned processes and may be redundant.

Amino Acid Sequence↗
PubMed2005

Cervical human papillomavirus screening by PCR: advantages of targeting the E6/E7 region.

PCR is a promising method for detection of human papillomavirus (HPV), the high-risk forms of which are responsible for cervical cancer. PCR primers that target the L1 or E1 region can be unreliable and may miss more advanced disease, whereas those directed at the E6 or E7 regions, which encode oncogenic products, are preferable because 1) the LI/E1 regions, but never the E6/E7 regions, are lost during integration of viral DNA into host genomic DNA, a process that can represent an integral component of progression from infection to tumorigenesis; and 2) the E6/E7 nucleotide sequence exhibits less nucleotide variation. The choice of region used for PCR has implications for HPV screening strategies in the clinical diagnosis and management of cervical cancer.

Female↗
PubMed2004

Chromatic and spatial properties of parvocellular cells in the lateral geniculate nucleus of the marmoset (Callithrix jacchus).

The parvocellular (PC) division of the afferent visual pathway is considered to carry neuronal signals which underlie the red-green dimension of colour vision as well as high-resolution spatial vision. In order to understand the origin of these signals, and the way in which they are combined, the responses of PC cells in dichromatic ('red-green colour-blind') and trichromatic marmosets were compared. Visual stimuli included coloured and achromatic gratings, and spatially uniform red and green lights presented at varying temporal phases and frequencies.The sensitivity of PC cells to red-green chromatic modulation was found to depend primarily on the spectral separation between the medium- and long-wavelength-sensitive cone pigments (20 or 7 nm) in the two trichromatic marmoset phenotypes studied. The temporal frequency dependence of chromatic sensitivity was consistent with centre-surround interactions. Some evidence for chromatic selectivity was seen in peripheral PC cells. The receptive field dimensions of parvocellular cells were similar in dichromatic and trichromatic animals, but the achromatic contrast sensitivity of cells was slightly higher (by about 30%) in dichromats than in trichromats. These data support the hypothesis that the primary role of the PC is to transmit high-acuity spatial signals, with red-green opponent signals appearing as an additional response dimension in trichromatic animals.

Algorithms↗
PubMed2004

WNK4 intron 10 polymorphism is not associated with hypertension.

A polymorphism in intron 10 of the serine-threonine kinase with no lysine (K) 4 gene WNK4 (G-->A, base 1156666 on chromosome 17) has recently been associated with essential hypertension in a white American population. We have attempted to replicate this finding in a well characterized cohort of 184 unrelated hypertensive Australians of British extraction in which biological power was enhanced by them each having 2 hypertensive parents. Controls were 219 normotensive ethnically matched subjects whose parents were both normotensive. Genotyping was performed using the homogeneous MassEXTEND Assay. This showed a frequency of 0.10 for the minor allele in each group (P=0.88). Moreover, blood pressure, body mass index, sex, and plasma lipid levels were similar across genotypes. In conclusion, our study provides no support for an association of the intron 10 variant of WNK4 with essential hypertension in the Anglo-Australian population studied.

Adult↗
PubMed2004

No association of angiotensin-converting enzyme 2 gene (ACE2) polymorphisms with essential hypertension.

Recent intriguing findings from genetic linkage, knockout, and physiologic studies in mice and rats led us to conduct the first investigation of the novel angiotensin-converting enzyme 2 gene (ACE2) in human hypertension (HT). We genotyped four single nucleotide polymorphisms (SNP) (A-->G at nucleotide 1075 in intron 1, G-->A at nucleotide 8790 in intron 3, C-->G at nucleotide 28330 in intron 11, and G-->C at nucleotide 36787 in intron 16) in HT (n = 152) and normotensive (NT, n = 193) groups having inherently high biological power (>80%) due to our inclusion only of subjects whose parents had the same BP status as themselves. The SNPs were in linkage disequilibrium (D' = 54% to 100%, P =.05 to 0.0001). Because ACE2 is on the X chromosome, data for each sex were analyzed separately. Minor allele frequencies in HT versus NT were as follows: for the intron 1 variant 0.21 versus 0.17 in female subjects (P =.31) and 0.25 versus 0.29 in male subjects (P =.60); intron 3 variant 0.22 versus 0.18 in female subjects (P =.35) and 0.15 versus 0.20 in male subjects (P =.47); intron 11 variant 0.39 versus 0.46 in male subjects (P = 0.17) and 0.31 versus 0.30 in male subjects (P =.96); intron 16 variant 0.20 versus 0.19 in female subjects (P =.72) and 0.17 versus 0.17 in male subjects (P =.95). Haplotype analysis was also negative. These data provide little support for ACE2 in genetic predisposition to HT.

Adult↗
PubMed2004

Egr-1 modulation of synapsin I expression: permissive effect of forskolin via cAMP.

A number of candidate Egr-1 neuronal target genes have been identified including the synapsin I gene. Previous studies have shown that over-expression of Egr-1 in cells transfected with an Egr-1 expression vector is sufficient to activate reporter genes linked to regions of the synapsin I promoter, but any effect on the expression of synapsin I within its genomic context has not been demonstrated. We tested our hypothesis that modulation of synapsin I expression by Egr-1 requires the presence of elevated cAMP which would normally be present during periods of neuronal plasticity. Both the adenyl cyclase activator, forskolin (frsk), and the cAMP analogue, Sp-Adenosine 3',5'-cyclic monophosphorothioate triethylammonium salt (Sp-cAMPS), enhanced the ability of Egr-1 to transactivate a CAT reporter plasmid containing multiple copies of the Egr-1 binding site (EBS). Furthermore, Egr-1 alone had minimal effects on synapsin I expression whereas forskolin treatment of PC12 cells profoundly affected the ability of Egr-1 to regulate synapsin I expression. These results suggest that Egr-1 transactivation during neuronal plasticity may rely on a permissive effect of cAMP.

Animals↗
PubMed2004

The atypical antipsychotic drug clozapine enhances chronic PCP-induced regulation of prefrontal cortex 5-HT2A receptors.

The ability of antipsychotic drugs to affect 5-HT(2A) receptor function has been widely suggested to contribute to their therapeutic properties. We have compared the ability of the antipsychotic drugs clozapine and haloperidol, alone and in combination with chronic phencyclidine (PCP), to modulate 5-HT(2A) receptor binding and mRNA. Acute (i.p. 45 min) and chronic (21-day) clozapine (osmotic minipump (OMP); 20 mg/kg/day) produced widespread decreases in 5-HT(2A) receptor binding (-60%-80%), measured using [(3)H]ketanserin autoradiography. Conversely, 5-HT(2A) mRNA levels, determined using in-situ hybridisation, were modestly increased by chronic clozapine treatment (+10%-30%). Chronic PCP treatment, at a dose (2.58 mg/kg i.p. intermittently for 28 days) that reproduces many of the neurochemical deficits of schizophrenia, decreased 5-HT(2A) receptor binding in the prefrontal cortex (PFC; -16%), consistent with the changes in post-mortem brain tissue from schizophrenic patients. Combined chronic PCP (i.p.) and clozapine (OMP) treatment down-regulated 5-HT(2A) receptor binding in many areas, similar to the effects of clozapine treatment alone and clozapine further enhanced the effects of PCP in the prefrontal cortex. In contrast 5-HT(2A) mRNA was not altered. Haloperidol treatment alone (1 mg/kg/day; OMP) and in combination with PCP (i.p.), generally produced no changes in 5-HT(2A) receptor protein or mRNA. Hence chronic PCP treatment, as employed here, mimics the decreased 5-HT(2A) receptor binding observed in the PFC of schizophrenic patients. Clozapine's enhancement of the natural response of PCP to down-regulate PFC 5-HT(2A) receptors may contribute to it's improved therapeutic profile against negative symptoms and cognitive deficits.

Animals↗
PubMed2004

Association of G-protein-coupled receptor kinase 4 haplotypes, but not HSD3B1 or PTP1B polymorphisms, with essential hypertension.

OBJECTIVE: To perform association studies of polymorphisms of the potential candidate essential hypertension (HT) genes GRK4, PTP1B and HSD3B1. METHODS: Subjects consisted of 168 unrelated, Caucasian essential hypertensive (HT) patients and 312 normotensive (NT) controls. Biological power was increased by ensuring subjects in each group had parents with the same blood pressure (BP) status as theirs. Three GRK4gamma variants (R65L, A142V and A486V), one HSD3B1 variant (T<---C Leu) and one PTP1B variant (1484insG) were genotyped by polymerase chain reaction and restriction enzyme digestion or by homogenous MassEXTEND Assay. RESULTS: The V allele of the A486V variant of GRK4gamma, but not the R65L or A142V variants, showed an association with HT (P = 0.02). The V allele was also associated with an elevation in systolic blood pressure (SBP) (P = 0.002). Although the L65 and the V142 alleles tracked with elevation in diastolic (DBP), this was seen only in male HTs (P = 0.009; P = 0.002, respectively). Haplotype frequencies differed between the HT and NT groups, particularly for the R, V, V haplotype combination of R65L, A142V and A486V, respectively. Neither of the HSD3B1 or PTP1B variants were associated with HT. CONCLUSION: Genetic variation in GRK4gamma was associated with HT in the subjects studied.

3-Hydroxysteroid Dehydrogenases↗
PubMed2003

HADHB, HuR, and CP1 bind to the distal 3'-untranslated region of human renin mRNA and differentially modulate renin expression.

Production of renin is critically dependent on modulation of REN mRNA stability. Here we sought to elucidate the molecular mechanisms involved. Transfections of renin-expressing Calu-6 cells with reporter constructs showed that a cis-acting 34-nucleotide AU-rich "renin stability regulatory element" in the REN 3'-untranslated region (3'-UTR) contributes to basal REN mRNA instability. Yeast three-hybrid screening with the REN 3'-UTR as bait isolated HADHB (hydroxyacyl-CoA dehydrogenase/3-ketoacyl-CoA thiolase/enoyl-CoA hydratase (trifunctional protein) beta-subunit) as a novel REN mRNA-binding protein. Recombinant HADHB bound specifically to the 3'-UTR of REN mRNA, as did the known mRNA stabilizers HuR and CP1 (poly(C)-binding protein-1). This required the renin stability regulatory element. Forskolin, which augments REN mRNA stability in Calu-6 cells, increased binding of several proteins, including HuR and CP1, to the REN 3'-UTR, whereas 4-bromocrotonic acid, a specific thiolase inhibitor, decreased binding and elevated renin protein levels. Upon decreasing HADHB mRNA with RNA interference, renin protein and mRNA stability increased, whereas RNA interference against HuR caused these to decrease. Immunoprecipitation and reverse transcription-PCR of Calu-6 extracts confirmed that HADHB, HuR, and CP1 each associate with REN mRNA in vivo. Intracellular imaging revealed distinct localization of HADHB to mitochondria, HuR to nuclei, and CP1 throughout the cell. Immunohistochemistry demonstrated enrichment of HADHB in renin-producing renal juxtaglomerular cells. In conclusion, HADHB, HuR, and CP1 are novel REN mRNA-binding proteins that target a cis-element in the 3'-UTR of REN mRNA and regulate renin production. cAMP-mediated increased REN mRNA stability may involve stimulation of HuR and CP1, whereas REN mRNA decay may involve thiolase-dependent pathways.

3' Untranslated Regions↗
PubMed2003

The structure of the zinc finger domain from human splicing factor ZNF265 fold.

Identification of the protein domains that are responsible for RNA recognition has lagged behind the characterization of protein-DNA interactions. However, it is now becoming clear that a range of structural motifs bind to RNA and their structures and molecular mechanisms of action are beginning to be elucidated. In this report, we have expressed and purified one of the two putative RNA-binding domains from ZNF265, a protein that has been shown to bind to the spliceosomal components U1-70K and U2AF35 and to direct alternative splicing. We show that this domain, which contains four highly conserved cysteine residues, forms a stable, monomeric structure upon the addition of 1 molar eq of Zn(II). Determination of the solution structure of this domain reveals a conformation comprising two stacked beta-hairpins oriented at approximately 80 degrees to each other and sandwiching the zinc ion; the fold resembles the zinc ribbon class of zinc-binding domains, although with one less beta-strand than most members of the class. Analysis of the structure reveals a striking resemblance to known RNA-binding motifs in terms of the distribution of key surface residues responsible for making RNA contacts, despite a complete lack of structural homology. Furthermore, we have used an RNA gel shift assay to demonstrate that a single crossed finger domain from ZNF265 is capable of binding to an RNA message. Taken together, these results define a new RNA-binding motif and should provide insight into the functions of the >100 uncharacterized proteins in the sequence data bases that contain this domain.

Amino Acid Sequence↗
PubMed2003

Association of coronary artery disease with glucocorticoid receptor N363S variant.

Overweight is associated with the N363S variant in the glucocorticoid receptor (encoded by nuclear receptor subfamily 3, group C, member 1 gene: NR3C1). The present study examined whether the N363S polymorphism might also be associated with coronary artery disease (CAD). This involved 556 patients with CAD, of which 437 were analyzed, and 302 control subjects, all being of Anglo-Celtic descent residing in Sydney. An extensive range of phenotypic parameters was collected from the patients, and leukocyte DNA from all subjects was genotyped by polymerase chain reaction-restriction fragment length polymorphism analysis for the A1218G (N363S) variant. Frequency of the S363 allele was 0.04 in healthy normal-weight control subjects but was 0.15 in patients with CAD (P=2.0x10(-5)) and was also elevated in subjects with CAD who were not overweight (0.14) (P=2.6x10(-5)), supporting a primary association with CAD. Frequency of S363 allele carriers in subjects with CAD who had angina was particularly high: unstable angina (0.45), stable angina (0.29), and no angina (0.26) (P for trend=0.016). Elevated cholesterol (P=0.027), triglycerides (P=0.005), and total cholesterol/HDL ratio (P=0.011), after Bonferroni, tracked with the S363 allele, consistent with accentuation of mechanisms that predispose to atheroma formation in coronary vessels. The data suggest a role for glucocorticoid receptor variation in the underlying cause of CAD.

Coronary Artery Disease↗
PubMed2003

Renin: from 'pro' to promoter.

Renin is the rate-limiting enzyme in a cascade that leads to production of angiotensin II, which is perhaps our most important regulator of salt and water balance and blood pressure. In this personal perspective, I describe how I entered the renin field 33 years ago by discovering that proteases increased the level of renin activity in biological fluids, so revealing the existence of a 'pro' form of the molecule. This led me on a journey that encapsulated all of the major milestones in molecular discovery for renin. These included (1) the elucidation of the steps in renin biosynthesis, (2) the cloning of renin cDNA and its gene, (3) demonstration of the structure of the renin protein, (4) using the renin gene in the first genetic studies in hypertension, (5) finding the mechanism by which the major controller, cyclic AMP, regulates the promoter, (6) showing that a strong enhancer and its weak promoter control this physiologically regulatable gene in accord with the variegation (on/off switching) model, and (7) being the first to identify molecules involved in posttranscriptional control. The renin molecule, its gene and molecular control are now very well understood, but more fine details on the topic of renin continue to emerge to delight 'reninologists' and others.

History, 20th Century↗
PubMed2003

Tumor necrosis factor receptor 2 mRNA in rat models of hypertension.

In human hypertension (HT) plasma tumor necrosis factor (TNF-alpha) and soluble TNF receptor 2 fragment (sTNF-R2) are increased, and the TNF-R2 gene (TNFRSF1B) has been implicated. Therefore, we measured Tnfr2 mRNA in kidney, adrenal, heart, and aorta from rats with ACTH-induced, corticosterone-induced, and spontaneous HT (SHR), and tested the effect of blockade of TNF-alpha by a recombinant TNF-R2 fragment (huTNFR:Fc) on development of HT in the ACTH model. Tnfr2 mRNA was quantified by real-time polymerase chain reaction, as were internal controls, beta-actin, and glyceraldehyde-3-phosphate dehydrogenase mRNA. The results showed no differences in tissue Tnfr2 mRNA between HT and control rats. The ACTH-induced HT was not affected by huTNFR:Fc coadministration. The findings thus offer no support for altered Tnfr2 expression in the rat models studied.

Adrenocorticotropic Hormone↗
PubMed2003

Association of obesity, but not diabetes or hypertension, with glucocorticoid receptor N363S variant.

OBJECTIVE: To determine whether the N363S variant in the glucocorticoid receptor (encoded by nuclear receptor subfamily 3, group C, member 1: NR3C1) is associated with obesity, type 2 diabetes, or hypertension. RESEARCH METHODS AND PROCEDURES: This was a cross-sectional case-control study involving 951 Anglo-Celtic/Northern European subjects from Sydney. This study consisted of the following: 1) an obesity clinic group, most of whom had "morbid obesity" (mean BMI for group = 43 +/- 8 kg/m(2); n = 152); 2) a type 2 diabetes clinic group (n = 356); 3) patients with essential hypertension who had a strong family history (n = 141); and 4) normal healthy controls (n = 302). N363S genotype, BMI, and a range of other parameters relevant to each group were measured. RESULTS: Compared with the frequency of 0.04 in nonobese healthy subjects, the S363 allele was significantly higher in obesity clinic patients (0.17; p = 5.6 x 10(-8)), subjects with diabetes who were also obese (0.09; p = 0.0045), subjects with hypertension who were also overweight (0.08; p = 0.0016), and overweight healthy subjects (0.12; p = 0.0004). DISCUSSION: The NR3C1 N363S variant is associated with obesity and overweight in a range of patient settings but is not associated with hypertension or type 2 diabetes.

Adult↗
PubMed2003

Induction of metabolic hypofunction and neurochemical deficits after chronic intermittent exposure to phencyclidine: differential modulation by antipsychotic drugs.

Numerous human imaging studies have revealed an absolute or relative metabolic hypofunction within the prefrontal cortex, thalamus and temporal lobes of schizophrenic patients. The former deficit correlates with cognitive deficits and negative symptoms, whereas the latter correlates with positive symptomologies. There is also general consensus that schizophrenia is associated with decreased parvalbumin expression in the prefrontal cortex. Since the drug phencyclidine can induce a psychosis resembling schizophrenia in humans, we have examined whether repeated phencyclidine (PCP) treatment to rats could produce similar metabolic and neurochemical deficits to those occurring in schizophrenia and whether these deficits could be modulated by antipsychotic drugs. We demonstrate here that chronic intermittent exposure to PCP (2.58 mg kg(-1) i.p.) elicits a metabolic hypofunction, as demonstrated by reductions in the rates of glucose utilization, within the prefrontal cortex, reticular nucleus of thalamus and auditory system, key structures displaying similar changes in schizophrenia. Moreover, chronic PCP treatment according to this regime also decreases parvalbumin mRNA expression in the rat prefrontal cortex and reticular nucleus of the thalamus. Chronic coadministration of haloperidol (1 mg kg(-1) day(-1)) or clozapine (20 mg kg(-1) day(-1)) with PCP did not modulate PCP-induced reductions in metabolic activity in the rat prefrontal cortex, but reversed deficits in the structures of the auditory system. Clozapine, but not haloperidol, reversed PCP-induced decreases in parvalbumin expression in prefrontal cortex GABAergic interneurons, whereas both drugs reversed the deficits in the reticular nucleus of the thalamus. These data provide important new information, which strengthen the validity of chronic PCP as a useful animal model of schizophrenia, when administered according to this protocol. Furthermore, we propose that reversal of PCP-induced reductions in parvalbumin expression in the prefrontal cortex may be a potential marker of atypical antipsychotic activity in relation to amelioration of cognitive deficits and negative symptoms of schizophrenia.

Animals↗