1991 — 1995 |
Morton, David B |
R29Activity Code Description: Undocumented code - click on the grant title for more information. |
Steroid Regulation of Peptide Sensitivity in the Cns
Steroid hormones induce long-term changes in the form and function of the nervous system. These changes are likely mediated via changes in the genome. The aim of this project is to use the steroid regulation of a peptide-mediated behavior of an insect, Manduca sexta, as a model for how steroids can control the responsiveness of the CNS. The ecdysteroids are steroid hormones which regulate the metamorphosis and molting of insects. One of the final steps in the molting process is the shedding (ecdysis) of the old cuticle. This behavior is triggered by the action of a neuropeptide, eclosion hormone (EH). The peptide can only act on the CNS, however, if the nervous system has been primed by exposure to the ecdysteroids. Studies that I have carried out indicate that the ecdysteroids act at two or more levels to regulate peptide responsiveness. Firstly on the receptor/2nd messenger (cGMP) system and secondly, inducing the de novo synthesis of two proteins (the EGPS) which are phosphorylated by the action of the peptide. Only when both of these components are functional will the nervous system respond to EH. The aim of this proposal is to examine the steroid regulation of both of these steps in detail. Using radiolabeled EH I will characterize the EH receptors and determine if they are up regulated in response to ecdysteroids. I will also elucidate the pathway by which EH elevates cGMP and ascertain if any element of this pathway is regulated by the ecdysteroids. I believe that the de novo synthesis of the EGPs is the final step in enabling the CNS to respond to EH. Once antibodies to the EGPs have been generated I will be able to follow their synthesis, the synthesis of the EGP mRNA(s) and their steroid regulation. Ultimately, I intend to isolate the steroid-regulated genes at each step in the cascade of EH action. The information gained from this proposal will be of importance to other studies in CNS plasticity which are believed to be regulated at the level of the genome.
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0.948 |
1995 — 1999 |
Morton, David B |
P01Activity Code Description: For the support of a broadly based, multidisciplinary, often long-term research program which has a specific major objective or a basic theme. A program project generally involves the organized efforts of relatively large groups, members of which are conducting research projects designed to elucidate the various aspects or components of this objective. Each research project is usually under the leadership of an established investigator. The grant can provide support for certain basic resources used by these groups in the program, including clinical components, the sharing of which facilitates the total research effort. A program project is directed toward a range of problems having a central research focus, in contrast to the usually narrower thrust of the traditional research project. Each project supported through this mechanism should contribute or be directly related to the common theme of the total research effort. These scientifically meritorious projects should demonstrate an essential element of unity and interdependence, i.e., a system of research activities and projects directed toward a well-defined research program goal. |
Characterization and Function of Steroid Regulated Genes in Manduca
Many cellular functions are regulated by change in genome expression. One major class of compounds which mediate these changes are hormones acting via members of the steroid/thyroid receptor superfamily. These hormone receptors alter gene expression by binding to specific regions of DNA and regulating transcription of adjacent genes. The nature of these regions of DNA and the functions of the genes regulated are of central importance to the understanding of normal physiological function, development and disease. Non-mammalian model systems have been invaluable in understanding the basic mechanisms of gene regulation by these hormones in all organisms. Studies by a number of investigators have shown the importance of using insects such as Drosophila melanogaster and Manduca sexta for such model systems. Both a rise in steroid levels and a decline can act as the signal which alters cellular function by an increase in the transcription of specific genes. The differences between the two mechanisms involved are, as yet, unclear. This project will use the insect, Manduca sexta, as a model system to characterize genes in the nervous system, whose transcription is increased by the declining levels of the steroid hormones, the ecdysteroids. Insect ecdysteroid receptors and their specific DNA binding sites have a high degree of homology with vertebrate steroid receptors, thus the mechanisms of regulation are likely to be conserved. We have isolated several genes from the nervous system of Manduca sexta whose transcripts increase in abundance as steroid levels decline. The specific steroid requirements for expression of one of these genes will be investigated with a combination of in vivo and in vitro manipulations of ecdysteroid levels. The transcription rate of this gene will be determined during development to test whether the regulation is at the transcriptional level. The effect of protein synthesis inhibitors on the levels of transcript will be determined and factors involved in the decline in transcript levels will be investigated. Studies on the regulatory regions of the gene and presence of potential regulatory proteins will be initiated. One long-term of this project is to determine the function of these genes in the development of the nervous system. An analysis of the developmental and spatial expression patterns of additional genes of this type will be completed to correlate the known physiological changes taking place in the nervous system with the presence of a particular transcript.
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0.948 |
1995 — 1999 |
Morton, David B |
P01Activity Code Description: For the support of a broadly based, multidisciplinary, often long-term research program which has a specific major objective or a basic theme. A program project generally involves the organized efforts of relatively large groups, members of which are conducting research projects designed to elucidate the various aspects or components of this objective. Each research project is usually under the leadership of an established investigator. The grant can provide support for certain basic resources used by these groups in the program, including clinical components, the sharing of which facilitates the total research effort. A program project is directed toward a range of problems having a central research focus, in contrast to the usually narrower thrust of the traditional research project. Each project supported through this mechanism should contribute or be directly related to the common theme of the total research effort. These scientifically meritorious projects should demonstrate an essential element of unity and interdependence, i.e., a system of research activities and projects directed toward a well-defined research program goal. |
Core--Central Services |
0.948 |
1996 — 2004 |
Morton, David B |
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. |
Regulation and Function of Cyclic Gmp in the Cns @ Oregon Health and Science University
DESCRIPTION: Many changes in the properties of the nervous system are brought about by chemical messengers such as neurotransmitters and neuromodulators. These frequently exert their effects by acting on cell surface receptors to change the concentrations of additional chemical messengers inside the cell. There are probably hundreds of different types of neurotransmitters and neuromodulators whereas there are only a handful of chemicals which have been identified as intracellular messengers and include cyclic AMP (cAMP), calcium, inositol (1,4,5) trisphosphate (InsP3) and cyclic GMP (cGMP). Many previous studies have highlighted the importance of cAMP, calcium and InsP3 in the function and plasticity of the nervous system. A number of important therapeutic drugs have been shown to exert their effects by interfering with these intracellular messenger cascades, such as lithium used for the treatment of bipolar disorder. By contrast, the regulation and functions of another intracellular messenger, cGMP, has received relatively little attention. This lab has been using the nervous system of the insect, Manduca sexta, as a model for cGMP regulation and function for several years and the applicants have shown that a behaviorally relevant neuropeptide, eclosion hormone (EH) exerts it effects by stimulating an increase in the cGMP levels in the nervous system of Manduca. The investigators have evidence to suggest that the peptide-stimulated increase in cGMP is mediated by additional messengers, possibly lipids, and one site of action of EH are the neurosecretory terminals in a neurohemal organ. This proposal aims to build on these observations to study, in more detail, the mechanisms involved in the increase in cGMP and to investigate possible functions for the increase in cGMP in neurosecretory terminals. The investigators have cloned several isoforms of the enzyme responsible for the synthesis of cGMP, guanylyl cyclase and intend to investigate their regulation and location in the CNS of Manduca. In particular, they will study the potential role of lipid messengers in the regulation of the guanylyl cyclases and which of the cyclases are expressed in the neurosecretory terminals where EH acts. EH stimulates an increase of cGMP in the neurosecretory terminals and they also intend to determine if this increase in cGMP regulates the release of neurohormones from these terminals. These studies will greatly increase our knowledge of the regulation and function of this relatively little studied messenger.
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2007 — 2015 |
Morton, David B |
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. |
Regulation and Function of Cgmp in the Nervous System @ Oregon Health &Science University
The long-term goal of this project is to understand how the properties of neurons are modulated by changes in oxygen concentration and cyclic GMP (cGMP). The intracellular messenger, cyclic GMP (cGMP), is a mediator of many physiological processes including vascular tone, kidney function, neural plasticity, cardiac muscle contractility and photoreceptor function. The levels of cGMP in a cell are regulated by a balance of its synthesis, by guanylyl cyclases (GCs), and its degradation, by phosphodiesterases. This project is aimed at increasing our understanding of the regulation and function of cGMP in the nervous system, focusing on a newly identified class of atypical soluble GCs (sGCs). Conventional sGCs are the primary targets for nitric oxide (NO). The atypical sGCs are poorly activated by NO. Examples are widespread, occuring in mammals and invertebrates such as insects and nematodes. Several lines of evidence strongly support the hypothesis that at least some examples of these atypical sGCs are molecular oxygen sensors. We plan to use the fruit fly, Drosophila melanogaster as a model to investigate the function and regulation of atypical sGCs and to test the hypothesis that they act as oxygen sensors providing information to the organism of the local oxygen concentration. Biochemical techniques will be used to directly assess the interaction of oxygen with the enzymes and physiological and behavioral analysis will examine the properties of the sensory neurons that express these sGCs to determine whether they act as oxygen sensors and mediate behavioral responses to hypoxia. One of the strengths of using Drosophila as a model system is the relative ease with which genetic manipulations can be carried out to modify the expression of the sGCs and a variety of exogenous gene products. The short-term and long-term physiological consequences of hypoxia in mammals are well known, however, the nature of the molecular oxygen sensor is still somewhat unclear. Our results will provide new information to understand how animals sense hypoxia. The results from this study will provide new insights and understanding of the cGMP pathway. The diversity of this signaling system is only now being,appreciated and the pharmaceutical industry is active in developing new compounds that specifically target cGMP regulation. These compounds promise to address a wide variety of health disorders including cardiovascular, urinary and neurological problems. Viagra and other pharmacological treatments for erectile disfunction are probably just the tip of the iceberg for compounds that target cGMP mediated processes.
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2011 — 2012 |
Morton, David B |
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.) |
Using Drosophila as a Model to Understand Tdp-43 Function in Als @ Oregon Health &Science University
DESCRIPTION (provided by applicant): Amyotrophic lateral sclerosis (ALS) is a devastating disease affecting about 2 in 100,000 people in the USA each year. Recent discoveries have the potential to dramatically change our understanding of the causes of ALS and identification of possible targets for treatment. ALS results from the selective loss of motor neurons, which in ALS patients contain cytoplasmic aggregates of proteins. Identification that a major constituent of these aggregates is the RNA-binding protein TDP-43, which is normally localized in the nucleus, has opened up many new directions in ALS research. A large number of mutations in TDP-43 have also been identified in ALS patients providing a causative link between this protein and the disease. TDP-43 aggregates have also been identified in post-mortem samples of patients who have died of other neurodegenerative diseases such as fronto-temporal dementias, Alzheimer's and Parkinson's diseases, suggesting that TDP-43 pathology might be a causative agent in a wide variety of diseases. It is critical to understand how TDP-43 dysfunction leads to disease. Two possible mechanisms have been proposed. The first is that the TDP-43 aggregates are inherently toxic and lead to motor neuron cell death. The second model, which is not mutually exclusive with the first, is that the loss of normally functioning protein in the nucleus is the proximate cause of motor neuron disruption. We are using the fruit fly, Drosophila melanogaster, as a model to understand the function of TDP- 43 in neurons and the consequences of aberrant expression. Null mutations in the Drosophila orthologue of TDP-43, named TBPH, are pupal lethal and show larval motor defects. Over-expression of any of three naturally occurring isoforms of TBPH in all tissues is early larval lethal. When expression is restricted to motor neurons, both larvae and adult flies have motor deficits. The bulk of the TDP-43 mutations in ALS are found in the C-terminal domain and our data shows that the C-terminal domain of TBPH is necessary for maximum toxicity. The primary goals of this application are to determine the cellular and molecular mechanisms underlying these defects. We have identified a genetic interaction between TBPH/TDP-43 and another neurodegeneration gene, named swiss cheese (sws), which suggests that sws is required for the toxic properties of TDP-43. This interaction is particularly intriguing because mutations in the human orthologue of sws, named neuropathy target esterase, lead to motor neuron disease. In addition to testing our hypothesis that the toxic effects of over-expressed TDP-43 result from an interaction between TDP-43 and sws we also propose to examine the anatomical and electrophysiological phenotypes of motor neurons that over-express TDP-43 in wild-type and sws mutant backgrounds. Any therapeutic approaches to treat ALS that rely on targeting TDP-43 dysfunction require an understanding of the molecular mechanisms that underlie the toxic effects of TDP-43. Using the powerful genetic tools available in Drosophila will greatly accelerate this understanding. PUBLIC HEALTH RELEVANCE: The first step in developing therapies for ALS is to identify the genes/proteins that either directly cause ALS or confer susceptibility to develop ALS in response to environmental triggers. Recent discoveries that strongly link TDP-43 to ALS suggest that this is a possible future target. Any therapeutic approaches to treat ALS that rely on targeting TDP-43 dysfunction require an understanding of the molecular mechanisms that underlie the toxic effects of TDP-43. This application focuses on understanding the mechanisms that lead to neurodegeneration by TDP-43 dysfunction using the fruit fly, Drosophila melanogaster as a model, an approach that will greatly speed up the process of designing therapies targeting TDP-43.
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2016 — 2017 |
Morton, David B |
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.) |
The Role of Microrna in the Cell Fate Specification of Photoreceptors @ Oregon Health & Science University
? DESCRIPTION (provided by applicant): Generation of distinct neuronal subtypes is a prerequisite for formation of a functional nervous system. For example, generation of rods and the three subtypes of cone cells in the mammalian retina are essential for receiving environmental light cues. Abnormal photoreceptor cell fate specification is frequently associated with retinal congenital and degenerative diseases and studies in the last decades have identified numerous photoreceptor cell fate determinant genes. Mutations in these genes are often linked to retinal developmental disorders and diseases. However, the molecular mechanisms underlying how these genes specify distinct photoreceptor subtypes and how they are regulated remains incomplete. This proposal is focused on understanding the regulatory mechanisms that determine a mutually exclusive binary choice between two photoreceptor cell fates using the fruit fly, Drosophila melanogaster. The conservation of the regulatory genes determining cell fate of photoreceptors between mammals and flies is remarkable. In mammals the choice between rods or cones is determined by the interplay between the cone-rod homeobox (Crx) protein and the neural retina-specific leucine zipper (NRL) protein. The Drosophila orthologues of these genes, Otd and Tj, regulate the choice of a specific photoreceptor between expressing one of two photo-pigments, rhodopsin 5 (Rh5) or rhodopsin 6 (Rh6). Our recent studies revealed that in Drosophila photoreceptors, the function of these genes is regulated by the Hippo signaling pathway, a signaling system that has also been shown to be highly conserved in regulating cell division and organ growth in both mammals and flies. Our preliminary studies have strongly suggested that multiple microRNAs are also involved in this photoreceptor subtype specification. microRNAs have been illustrated playing important regulatory roles in various developmental and disease processes, but their role in photoreceptor subtype fate specification is still unknown. In this proposal, we will use genetic and molecular approaches to elucidate how these microRNAs specify photoreceptor subtype fates by regulating conserved fate determinant genes and the photo-pigment genes. In addition, we will investigate how the biogenesis of these microRNAs is regulated by the newly identified Hippo signaling pathway. These studies will provide novel molecular mechanisms underlying neuronal subtype fate specification that will help understand the basis for a variety of developmental disorders and potentially aid in the design of strategies for directed differentiation of human pluripotent cells into specific cell types to replace the damaged cells in degenerative neuronal tissues.
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