Expression of immune genes on chromosome 6p21.3-22.1 in schizophrenia.

Schizophrenia is a common mental illness with a large genetic component. Three genome-wide association studies have implicated the major histocompatibility complex gene region on chromosome 6p21.3-22.

Promoter methylation and tissue-specific transcription of the α7 nicotinic receptor gene, CHRNA7.

The α7 nicotinic acetylcholine receptor is known to regulate a wide variety of developmental and secretory functions in neural and non-neural tissues. The mechanisms that regulate its transcription in these varied tissues are not well understood. Epigenetic processes may play a role in the tissue-specific regulation of mRNA expression from the α7 nicotinic receptor subunit gene, CHRNA7.

Multiple genes in the 15q13-q14 chromosomal region are associated with schizophrenia.

Objective: The chromosomal region, 15q13-q14, including the α7 nicotinic acetylcholine receptor gene, CHRNA7, is a replicated region for schizophrenia. This study fine-mapped genes at 15q13-q14 to determine whether the association is unique to CHRNA7.

Methods: Family-based and case-control association studies were performed on Caucasian-non-Hispanic and African-American individuals from 120 families as well as 468 individual patients with schizophrenia and 144 well-characterized controls.

Differential regulation of alpha7 nicotinic receptor gene (CHRNA7) expression in schizophrenic smokers.

The alpha7 neuronal nicotinic receptor gene (CHRNA7) has been implicated in the pathophysiology of schizophrenia by genetic and pharmacological studies. Expression of the alpha7* receptor, as measured by [(125)I]alpha-bungarotoxin autoradiography, is decreased in postmortem brain of schizophrenic subjects compared to non-mentally ill controls. Most schizophrenic patients are heavy smokers, with high levels of serum cotinine.

A 2-base pair deletion polymorphism in the partial duplication of the alpha7 nicotinic acetylcholine gene (CHRFAM7A) on chromosome 15q14 is associated with schizophrenia.

Multiple genetic linkage studies support the hypothesis that the 15q13-14 chromosomal region contributes to the etiology of schizophrenia. Among the putative candidate genes in this area are the alpha7 nicotinic acetylcholine receptor gene (CHRNA7) and its partial duplication, CHRFAM7A. A large chromosomal segment including the CHRFAM7A gene locus, but not the CHRNA7 locus, is deleted in some individuals.

Association of the 5'-upstream regulatory region of the alpha7 nicotinic acetylcholine receptor subunit gene (CHRNA7) with schizophrenia.

Background: The alpha7 neuronal nicotinic acetylcholine receptor subunit gene (CHRNA7) is localized in a chromosomal region (15q14) linked to schizophrenia in multiple independent studies. CHRNA7 was selected as the best candidate gene in the region for a well-documented endophenotype of schizophrenia, the P50 sensory processing deficit, by genetic linkage and biochemical studies.

Methods: Subjects included Caucasian-Non Hispanic and African-American case-control subjects collected in Denver, and schizophrenic subjects from families in the NIMH Genetics Initiative on Schizophrenia.

Regulation of a novel alphaN-catenin splice variant in schizophrenic smokers.

The alphaN-catenin (CTNNA2) gene represents a promising candidate gene for schizophrenia based upon previous genetic linkage, expression, and mouse knockout studies. CTNNA2 is differentially regulated by smoking in schizophrenic patients. In this report, the genomic structure of a primate-specific alphaN-catenin splice variant (alphaN-catenin III) is described.

Comparison of polymorphisms in the alpha7 nicotinic receptor gene and its partial duplication in schizophrenic and control subjects.

The hypothesis that the 15q13-15 region of chromosome 15 contains a gene that contributes to the etiology of schizophrenia is supported by multiple genetic linkage studies. The alpha7 neuronal nicotinic acetylcholine receptor (CHRNA7) gene was selected as the best candidate gene in this region for molecular investigation, based on these linkage findings and biological evidence in both human and rodent models. CHRNA7 receptors are decreased in expression in postmortem brain of schizophrenic subjects.

Association of promoter variants in the alpha7 nicotinic acetylcholine receptor subunit gene with an inhibitory deficit found in schizophrenia.

Background: The alpha7 neuronal nicotinic acetylcholine receptor subunit gene (CHRNA7) has been implicated as a candidate gene for schizophrenia, and for an auditory sensory processing deficit found in the disease, by both genetic linkage at 15q14 and biochemical data. The expression of CHRNA7 is reduced in several brain regions in schizophrenic subjects compared with control subjects. This study presents DNA sequence analysis of the core promoter region for CHRNA7 in schizophrenic and control subjects.

Smoking and mental illness.

Patients with mental illness have a higher incidence of smoking than the general population and are the major consumers of tobacco products. This population includes subjects with schizophrenia, manic depression, depression, posttraumatic stress disorder (PTSD), attention-deficit disorder (ADD), and several other less common diseases. Smoking cessation treatment in this group of patients is difficult, often leading to profound depression.

[(3)H]Nicotine binding in peripheral blood cells of smokers is correlated with the number of cigarettes smoked per day.

The principal sites for biological action of tobacco products are thought to be the nicotinic acetylcholine receptors (nAChR). Nicotinic receptor subunit genes, therefore, represent an important gene family for study in nicotine addiction. They are localized in both brain and in the periphery.

Abnormal regulation of high affinity nicotinic receptors in subjects with schizophrenia.

Previous studies have suggested that an abnormality in neuronal nicotinic acetylcholine receptor expression or function may be involved in the neuropathophysiology of schizophrenia. [(3)H]-nicotine and [(3)H]-epibatidine binding were compared in postmortem brain from control and schizophrenic subjects with varying smoking histories. In control subjects, increased receptor binding was seen in hippocampus, cortex, and caudate with increasing tobacco use.

Genomic organization and partial duplication of the human alpha7 neuronal nicotinic acetylcholine receptor gene (CHRNA7).

The human alpha7 neuronal nicotinic acetylcholine receptor gene (HGMW-approved symbol CHRNA7) has been characterized from genomic clones. The gene is similar in structure to the chick alpha7 gene with 10 exons and conserved splice junction positions. The size of the human gene is estimated to be larger than 75 kb.

Comparison of the regional expression of nicotinic acetylcholine receptor alpha7 mRNA and [125I]-alpha-bungarotoxin binding in human postmortem brain.

Neuronal nicotinic acetylcholine receptors are expressed in the human central nervous system. A specific subtype of this receptor family, the alpha7 nicotinic acetylcholine receptor, is thought to be the principal alpha-bungarotoxin (alphaBTX)-binding protein in mammalian brain. Although the expression of this receptor subtype has been characterized in rat, no study has specifically compared the expression of both the alpha7 gene and the localization of BTX binding sites in human brain.

Effect of smoking history on [3H]nicotine binding in human postmortem brain.

Chronic nicotine administration in animal models evokes a dose-dependent increase in brain nicotinic receptor numbers. Genetically determined variability in nicotinic receptor number in different mouse strains has also been reported, which is thought to affect sensitivity to nicotine, as well as the development of tolerance. Humans self-administer nicotine principally in the form of cigarettes and other tobacco products.

Regional gene expression of the glutamate receptor subtypes GluR1, GluR2, and GluR3 in human postmortem brain.

Although glutamatergic receptors are localized throughout the mammalian central nervous system (CNS), the specific cellular localization of the various glutamatergic receptor subtypes throughout human brain remains largely unknown. PCR fragments to human GluR1, GluR2, and GluR3 receptor subtypes were cloned and used as probes for in situ hybridization in order to examine the anatomical and cellular localization of glutamate receptor subtype gene expression in dissected regions of human postmortem brain tissue. Although hybridization was observed throughout the CNS, results indicated that the highest levels of hybridization were in the hippocampus, with localization primarily to cells in the pyramidal cell layer of the CA1-CA3 region, and the granular cells of the dentate gyrus.

Acidic and basic fibroblast growth factor mRNAs are increased in striatum following MPTP-induced dopamine neurofiber lesion: assay by quantitative PCR.

Acidic fibroblast growth factor (aFGF) and basic fibroblast growth factor (bFGF), the two best characterized members of a growing family of heparin-binding growth factors, have been shown to affect both survival of cultured neurons and regeneration of nerve terminals when applied exogenously. The endogenous expression of these growth factors in response to brain injury is not well understood. We have utilized the Swiss-Webster mouse, treated with the neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), and a quantitative polymerase chain reaction assay to examine changes in endogenous synthesis of mRNA for both aFGF and bFGF in the striatum and substantia nigra.

Biological stability of mRNA isolated from human postmortem brain collections.

RNA isolated from frozen human postmortem brain tissue was evaluated for its utility in molecular biological studies. Samples varying in postmortem interval, delay period before freezing, and long-term freezer storage were analyzed. It was found that storage of human postmortem brain at -70 degrees C for more than 5 years may compromise its use for oligo-dT primed library construction and in vitro expression studies.

Synthesis of cRNA probes from PCR-generated DNA.

We have compared RNA polymerase promoter activities in PCR-generated DNA fragments for use in the in vitro transcription of cRNA probes. Sense oligonucleotide primers, specific for the mouse acidic fibroblast growth factor gene, were synthesized with 5' extensions containing promoter sequences for the T7, T3 and SP6 RNA polymerase promoters. A common antisense primer was used with each of the promoter/aFGF primers to prepare PCR-generated DNA fragments (minigenes).

Endogenous sterol synthesis is not required for regulation of 3-hydroxy-3-methylglutaryl coenzyme A reductase by low density lipoprotein.

It has been proposed that an endogenously synthesized oxysterol mediates the regulation of cholesterol biosynthesis by low density lipoprotein in cultured mammalian cells. Studies in this report demonstrate that under conditions in which squalene conversion to sterols is blocked either by inhibition of squalene cyclization or lanosterol demethylation, or both, low density lipoprotein regulates 3-hydroxy-3-methylglutaryl coenzyme A reductase normally. These observations rule out the hypotheses that either an endogenously synthesized oxygenated cholesterol biosynthetic intermediate or epoxysterol is required to mediate the inhibition of this enzyme by low density lipoprotein.

Requirement for 24(S),25-epoxycholesterol for the viability of cultured fibroblasts.

Previous studies on a somatic cell mutant auxotrophic for mevalonate (Mev-1) have shown that these cells rapidly lose viability when deprived of mevalonic acid in culture medium supplemented with serum cholesterol. Testing of all known end products of mevalonate metabolism in cultured mammalian cells has been conducted to determine the basis for this mevalonate requirement. It has been found that the recently discovered mevalonate metabolite 24(S),25-epoxycholesterol produces a partial restoration of viability of Mev-1 cells starved for mevalonate, whereas other structurally similar oxysterols do not.

A somatic cell mutant with a kinetically altered 3-hydroxy-3-methylglutaryl coenzyme A reductase.

A somatic cell mutant has been isolated which is resistant to killing and growth inhibition by mevinolin, a competitive inhibitor of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase. The resistance phenotype is dominant with respect to the wild-type cell and can largely be ascribed to a 6-7-fold lowering of the KM for HMG-CoA. We thus conclude that mevinolin resistance can be utilized to obtain a genetic marker for the structural gene encoding HMH-CoA reductase.

Defective macromolecule biosynthesis and cell-cycle progression in a mammalian cell starved for mevalonate.

The isolation of a somatic cell mutant (Mev-1) with a block in one of the mevalonate-biosynthesizing enzymes (3-hydroxy-3-methylglutaryl-coenzyme A synthase, EC 4.1.3.

Analysis of the coordinate expression of 3-hydroxy-3-methylglutaryl coenzyme A synthase and reductase activities in Chinese hamster ovary fibroblasts.

Decreased activities of both 3-hydroxy-3-methylglutaryl coenzyme A (HMG CoA) synthase and HMG CoA reductase are observed in the presence of sterol in the Chinese hamster ovary (CHO) fibroblast. In three different genotypes of CHO cell mutants resistant to 25-hydroxycholesterol both enzyme activities exhibit a decreased response to 25-hydroxycholesterol compared to wild-type cells. Permanently repressed levels of both HMG CoA synthase and HMG CoA reductase activities are observed in another CHO mutant, phenotypically a mevalonate auxotroph.

Inhibition of degradation of 3-hydroxy-3-methylglutaryl coenzyme A reductase by mevinolin.

Mevinolin is demonstrated to inhibit the degradation of 3-hydroxy-3-methylglutaryl-CoA reductase in Chinese hamster ovary cells. Evidence is presented that this effect of mevinolin is not general to degradation of total cellular proteins and is not due to the block to mevalonate synthesis produced by this compound.