1997 — 2000 |
Schmauss, Claudia |
R01Activity Code Description: To support a discrete, specified, circumscribed project to be performed by the named investigator(s) in an area representing his or her specific interest and competencies. |
D3 Premrna Processing in Chronic Psychosis @ Columbia University Health Sciences
DESCRIPTION (Adapted from applicant's abstract): The D2-class of dopamine receptors are targets for drugs with proven antipsychotic efficacy and have been repeatedly suggested as factors in the pathophysiology of schizophrenia. Although studies have failed to demonstrate a genetic link, studies on brain tissues obtained postmortem from long-term hospitalized patients with chronic psychosis suggest an abnormal posttranscriptional processing of dopamine D3-receptor-encoded pre-mRNA. This results in a decreased expression of D3 mRNA and an increased accumulation of an alternatively spliced, truncated D3-like mRNA, named D3nf. In order to pursue a more detailed investigation of the expression of D3 and D3nf mRNA and protein in postmortem tissues, and in order to begin to examine potential functional consequences of the enhanced D3nf-specific splicing of D3 pre-mRNA in chronic psychosis, it is proposed: (1) To perform RNase protection assays to determine the relative abundance of D3 and D3nf mRNA in defined anatomic regions of brains obtained postmortem from patients with chronic schizophrenia, bipolar affective disorders, and from controls. (2) To perform immunoprecipitation and immunoblot experiments with D3-specific monoclonal antibodies and a D3nf-specific polyclonal antiserum to determine whether (in the same anatomic regions) alterations in D3 and D3nf mRNA expression also result in corresponding changes in the expression of the respective proteins. (3) Furthermore, because co-expression of D3nf in stably D3-expressing rat GH3 cells increases the electrophoretic mobility of D3-immunoreactivity (from 50 kD to 180 kD), and because this co-expression appears to render a significant proportion of D3 receptors inaccessible to ligands, experiments on stably and inducibly D3, D3nf, and D3/D3nf expressing GH3 cells are proposed that aim at determining the protein composition of the D3nf-induced 180 kd D3-immunoreactivity, its posttranslational modifications, the kinetics of its formation, and its stability. In addition, radioligand binding studies are proposed to determine the Bmax of (3H)quinpirole binding of membranes of D3 and D3/D3nf-expressing cells. Finally, it will be tested in transfected polarized epithelial cells (MDCK) whether the membrane targeting of the D3 protein is altered in the presence of D3nf. Results of these studies are expected to provide insight into the extent to which the expression of D3 and D3nf mRNA and protein is altered in schizophrenia, and they will begin to elucidate the influence of D3nf expression of D3 receptor expression and function.
|
1 |
2001 — 2003 |
Schmauss, Claudia |
R01Activity Code Description: To support a discrete, specified, circumscribed project to be performed by the named investigator(s) in an area representing his or her specific interest and competencies. |
5-Ht2c-Receptor Expression and Function in Depression @ Columbia University Health Sciences
DESCRIPTION: (Applicant's abstract) The expression and function of one subtype of serotonin (5-HT) receptors, the 5-HT2C receptor, is regulated by RNA editing and alternative splicing of its encoded pre-mRNA. In postmortem prefrontal cortical tissue from depressed suicide victims, the editing pattern of 5-HT2C pre-mRNA differs significantly from the editing pattern of control brains that could potentially result in a decreased efficiency of 5-HT2C receptor-G protein interactions. The overall objectives of the proposed research plan are to varify further a possible relationship between depression and an altered editing pattern of prefrontal cortical 5-HT2C pre-mRNA, and to define the possible functional consequences of this altered editing pattern and to test possible underlying mechanisms. Three specific aims are proposed to attain these objectives. In specific aim 1, the investigator proposes an extended replication of the differential 5-HT2C editing finding piloting this work. The 5-HT2C receptor editing pattern would be compared in brains of groups of male depressed suicide victims and depressed non-suicide subjects to assess the relative contribution of depression versus suicide. Editing patterns of 5-HT2C receptor mRNAs would be identified by nucleotide sequencing of cDNAs generated by RT-PCR. Proposed specific aim 2 would assess the functional significance of altered 5 HT2C receptor mRNA editing using stably transfected lines of NIH3T3 cells that express the three major altered 5-HT2C receptor isoforms associated with depression, as well as the more rare nonedited and fully edited isoforms. Functional assays would determine the comparative ability of the edited and nonedited isoforms to couple to G protein and activate the phospholipase C second messenger system. The effects of RNA editing on the guanyl nucleotide sensitivity of 5-HT2C receptor-G protein interactions, and the interaction of different receptor isoforms would also be preliminarily assessed. Related functional experiments would compare GTP(S binding to membranes of prefrontal cortical tissues of depressed suicide victims and depressed non-suicide subjects to determine the effect of 5-HT2C editing alterations associated with depression on basal and agonist-promoted activation of G proteins by 5-HT2C receptors. Specific aim 3 would compare the effects of mechanistically distinct antidepressants, and the 5-HT2A/2C receptor antagonist ketanserin, on the neocortical 5-HT2C receptor RNA editing pattern, in wild-type mice. These studies would attempt to assess whether the observed alteration of 5-HT2C RNA editing in depression reflects medication effects.
|
1 |
2005 |
Schmauss, Claudia |
R56Activity Code Description: To provide limited interim research support based on the merit of a pending R01 application while applicant gathers additional data to revise a new or competing renewal application. This grant will underwrite highly meritorious applications that if given the opportunity to revise their application could meet IC recommended standards and would be missed opportunities if not funded. Interim funded ends when the applicant succeeds in obtaining an R01 or other competing award built on the R56 grant. These awards are not renewable. |
5-Ht2c Receptor Expression and Function in Depression @ Columbia University Health Sciences |
1 |
2008 — 2011 |
Schmauss, Claudia |
R01Activity Code Description: To support a discrete, specified, circumscribed project to be performed by the named investigator(s) in an area representing his or her specific interest and competencies. |
Genetic and Environmental Modulation of Rna Editing @ Columbia University Health Sciences
[unreadable] DESCRIPTION (provided by applicant): Early life stress is a prominent risk factor for adult-onset depressive illness. In both humans and rodents, early life stress leads to changes in several physiological measures that persist into adulthood. In a genetically distinct inbred strain of mice with lower forebrain serotonin, spontaneously elevated anxiety, and increased stress reactivity (Balb/c), early life stress leads to several changes in neuronal gene expression in adulthood. These changes include increased expression of serotonin 2C (5-HT2C) receptor mRNA isoforms that result from RNA editing and encode receptors with reduced function. Such changes in 5-HT2C receptor editing have also been found in brains of depressed suicide victims. Studies on Balb/c mice showed that changes in 5-HT2C receptor editing are accompanied by altered expression of the alpha subunit of Gq protein that couples to this receptor. They further showed that treatment with the antidepressant drug fluoxetine during adolescence significantly decreased the abnormally increased 5-HT2C pre-mRNA editing that resulted from early life stress and also reversed corresponding alterations in G alpha q protein expression. Similar to the effect of adolescent fluoxetine in mice exposed to early life stress, postweaning environmental enrichment diminished the magnitude of hightened behavioral responses to adult stress. However, in contrast to fluoxetine, postweaning enrichment did not alter the abnormal 5-HT2C pre-mRNA editing phenotype. In this proposal, a cross-fostering paradigm between Balb/c and stress-resistant C57Bl/6 mice is used to test the impact of genetic factors, environmental factors, and adolescent antidepressant treatment on the modulation of 5-HT2C receptor editing phenotypes. It further tests potential mechanisms leading to increased 5-HT2C pre-mRNA editing in Balb/c mice exposed to early life stress. One hypothesis is that early life stress alters the expression of distinct isoforms of the editing enzymes ADAR1/2 via alternative splicing to yield mRNA encoding enzymes with higher catalytic activities. Another hypothesis, tested with studies on transfected cells, is that G alpha q protein is a critical mediator of the serotonin-dependent regulation of 5-HT2C pre-mRNA editing. Finally, molecular and anatomic studies will demonstrate that changes in 5-HT2C pre-mRNA editing that result from early life stress are also accompanied by changes in the expression of other genes that are either potential mediators of epigenetic changes in gene expression, transcriptional or post-transcriptional modulators of gene expression, or involved in synaptic functions, and that many of these changes in gene expression are functionally linked to depression and differentially modulated by genetic factors, environmental influences, and antidepressant treatment.
|
1 |
2013 — 2014 |
Schmauss, Claudia |
R21Activity Code Description: To encourage the development of new research activities in categorical program areas. (Support generally is restricted in level of support and in time.) |
Epigenetic Modulation of Antidepressant Efficacy @ Columbia University Health Sciences
DESCRIPTION (provided by applicant): Mood disorders are the second leading cause of disability worldwide. Their treatment relies predominantly on antidepressant drugs that target brain monoamines, including selective serotonin-reuptake inhibitors (SSRIs). However, even after the prolonged treatment, the antidepressant effects vary considerably, with only a small faction of patients exhibiting significant treatment effects. Since the pathogenesis of mood disorders is complex, with different contributions of genetic risk, environmental influences, and epigenetic phenotypes in individuals with the same diagnosis, the concept of a more personalized therapy is gaining increasing momentum, especially for subjects with a history of early life stress (ELS), a prominent risk factor for mood disorders and one of the strongest predictors of poor treatment response. This exploratory proposal targets the treatment of this population of patients and aims at linking the antidepressant efficacy of SSRIs to the patient's epigenetic phenotype. A recent study from this laboratory showed that a stress-susceptible strain of mice (Balb/c) exposed to ELS exhibits an adaptive epigenetic response to ELS, namely increased acetylation of histone H4 protein in the frontal cortex, that ameliorates the severity of the adult emotional psychopathology associated with ELS exposure. Strikingly, adolescent fluoxetine treatment of ELS Balb/c mice exerted powerful antidepressant effects and further elevated levels of acetylated histone H4 protein. These findings motivated the behavioral and molecular studies on different mouse strains proposed here that test the hypothesis that the effect of fluoxetine on histone H4 acetylation is a critical determinant of antidepressant efficacy and that enhanced serotonergic signaling and reduced activity of histone deacetylases (HDACs) lead to this effect. Studies on ELS Balb/c mice with reduced HDAC activity investigate the role of increased serotonergic signaling in stimulating histone H4 acetylation by comparing the effects of adolescent treatments with antidepressant drugs that either increase serotonin (5-HT) levels in the brain (fluoxetine) or that do not alter them (tianeptine). They also examine the role of 5-HT1A and 5-HT2 receptors as well as the role of brain derived neurotrophic factor-mediated trkB-signaling in mediating this effect. Additional studies on C57Bl/6 serotonin-transporter knockout mice with elevated forebrain 5-HT levels and no response to fluoxetine investigate whether reducing HDAC activity alone is sufficient to elevate histone H4 acetylation and to rescue antidepressant treatment response. Finally, studies on two additional strains of mice with low responsiveness to fluoxetine test whether co-treatment with fluoxetine and an HDAC inhibitor enhances antidepressant effects, and whether reducing HDAC activity during adolescence or adulthood has the same effect on histone H4 acetylation and antidepressant treatment response. In all studies, the possibility that drug-induced changes in histone H4 acetylation in brain are also found in peripheral blood lymphocytes will be explored. Positive results from these studies could identify a new biomarker capable of predicting antidepressant treatment response.
|
1 |