SMN Control of snRNP Biogenesis: Role in RNA Splicing and Motor Neuron Survival

Summary

Principal Investigator: Livio Pellizzoni
Abstract: DESCRIPTION (provided by applicant): Project Summary Regulation of RNA splicing is the primary mechanism responsible for generating the proteome diversity and phenotypic complexity of humans. This post-transcriptional regulatory mechanism is particularly prominent in neuronal cells and the increasing number of neurodegenerative disorders that are associated with splicing dysfunction underscores its biological relevance. The study of the survival motor neuron (SMN) protein provides a unique opportunity to address the basic biology of splicing regulation and the role of RNA dysfunction in human disease. Reduced SMN levels cause spinal muscular atrophy (SMA)-a common inherited neuromuscular disorder characterized by motor neuron degeneration. SMN has a well-established function in the assembly of small nuclear ribonucleoproteins (snRNPs), which are the essential components of the splicing machinery. In SMA mice, the degree of snRNP assembly impairment correlates with disease severity and causes an uneven rather than uniform decrease in the levels of snRNPs, resulting in the alteration of the snRNP profile of tissues. Moreover, restoration of normal snRNP levels coincides with phenotypic correction in animal models of disease. Despite these advances, how defective SMN function in snRNP biogenesis selectively affects motor neurons is unknown. This project will investigate our hypothesis that SMN functions to endow distinct cell types with unique snRNP profiles for the purpose of splicing regulation and that alterations in this process triggered by SMN deficiency cause splicing defects in mRNAs critical for motor neuron biology. Building on the results of our preliminary studies, in Aim 1 we will analyze SMN role in establishing distinct snRNP profiles in different cell types as well as mouse tissues during development. The relevance for splicing regulation of these cell type-specific snRNP profiles will be studied in Aims 2 and 3. In Aim 2, we will investigate the consequences of SMN depletion on RNA splicing using microarray analyses and cellular model systems with regulated knockdown of SMN. Based on our ability to generate large numbers of motor neurons differentiated from mouse embryonic stem (ES) cells with normal and reduced levels of SMN, we will identify mRNAs affected by SMN deficiency in the cell type relevant to SMA. Through comparative analyses using other types of post-mitotic neurons as well as primary motor neurons from SMA mice, we will define the set of mRNAs whose expression or alternative splicing is selectively affected in motor neurons. In order to establish a mechanistic link between SMN control of snRNP biogenesis and splicing regulation, the cause-effect relationship between SMN-dependent alterations in the snRNP profile and splicing changes will be analyzed in Aim 3. Finally, in Aim 4, the functional role of selected genes and alternative splicing isoforms identified above will be studied using knockdown and over-expression experiments in both normal and SMN- deficient ES cell-derived motor neurons. This approach should identify mRNAs whose SMN-dependent expression or alternative splicing is critical for motor neuron survival and function. PUBLIC HEALTH RELEVANCE: Project Narrative The biomedical relevance of understanding the mechanisms and regulation of RNA processing is highlighted by the growing list of human genetic disorders associated with defects in RNA metabolism. This project is designed to define the normal role of the spinal muscular atrophy (SMA) protein in the post-transcriptional control of gene expression as well as to identify genes whose altered expression may contribute to degeneration of SMN-deficient motor neurons, the neuronal cells selectively affected in SMA. These studies should provide insights into the basic mechanisms of RNA regulation and the molecular defects underlying SMA pathogenesis with the potential of identifying new candidate targets for therapeutic development.
Funding Period: 2010-04-15 - 2015-03-31
more information: NIH RePORT

Top Publications

  1. pmc Postsymptomatic restoration of SMN rescues the disease phenotype in a mouse model of severe spinal muscular atrophy
    Cathleen M Lutz
    The Jackson Laboratory, Bar Harbor, Maine 04609, USA
    J Clin Invest 121:3029-41. 2011
  2. pmc A role for SMN exon 7 splicing in the selective vulnerability of motor neurons in spinal muscular atrophy
    Matteo Ruggiu
    Department of Pathology and Cell Biology, Columbia University, New York, New York, USA
    Mol Cell Biol 32:126-38. 2012
  3. pmc SMN is required for sensory-motor circuit function in Drosophila
    Wendy L Imlach
    Center for Motor Neuron Biology and Disease, Columbia University Medical Center, 630 West 168th Street, New York, NY 10032, USA
    Cell 151:427-39. 2012
  4. pmc An SMN-dependent U12 splicing event essential for motor circuit function
    Francesco Lotti
    Department of Pathology and Cell Biology, Columbia University, New York, NY 10032, USA
    Cell 151:440-54. 2012
  5. pmc The DcpS inhibitor RG3039 improves motor function in SMA mice
    James P Van Meerbeke
    These authors contributed equally to this study
    Hum Mol Genet 22:4074-83. 2013
  6. pmc A cell system for phenotypic screening of modifiers of SMN2 gene expression and function
    Darrick K Li
    Center for Motor Neuron Biology and Disease, Columbia University, New York, New York, United States of America
    PLoS ONE 8:e71965. 2013
  7. pmc SMN is essential for the biogenesis of U7 small nuclear ribonucleoprotein and 3'-end formation of histone mRNAs
    Sarah Tisdale
    Center for Motor Neuron Biology and Disease, Columbia University, New York, NY 10032, USA Department of Pathology and Cell Biology, Columbia University, New York, NY 10032, USA
    Cell Rep 5:1187-95. 2013
  8. ncbi SMN control of RNP assembly: from post-transcriptional gene regulation to motor neuron disease
    Darrick K Li
    Center for Motor Neuron Biology and Disease, Columbia University, New York, NY 10032, USA Department of Pathology and Cell Biology, Columbia University, New York, NY 10032, USA
    Semin Cell Dev Biol 32:22-9. 2014

Detail Information

Publications8

  1. pmc Postsymptomatic restoration of SMN rescues the disease phenotype in a mouse model of severe spinal muscular atrophy
    Cathleen M Lutz
    The Jackson Laboratory, Bar Harbor, Maine 04609, USA
    J Clin Invest 121:3029-41. 2011
    ..Nevertheless, our results suggest that even in severe SMA, timely reinstatement of the SMN protein may halt the progression of the disease and serve as an effective postsymptomatic treatment...
  2. pmc A role for SMN exon 7 splicing in the selective vulnerability of motor neurons in spinal muscular atrophy
    Matteo Ruggiu
    Department of Pathology and Cell Biology, Columbia University, New York, New York, USA
    Mol Cell Biol 32:126-38. 2012
    ..These findings suggest a mechanism to explain the selective vulnerability of motor neurons to loss of SMN1...
  3. pmc SMN is required for sensory-motor circuit function in Drosophila
    Wendy L Imlach
    Center for Motor Neuron Biology and Disease, Columbia University Medical Center, 630 West 168th Street, New York, NY 10032, USA
    Cell 151:427-39. 2012
    ..These results establish sensory-motor circuit dysfunction as the origin of motor system deficits in this SMA model and suggest that enhancement of motor neural network activity could ameliorate the disease...
  4. pmc An SMN-dependent U12 splicing event essential for motor circuit function
    Francesco Lotti
    Department of Pathology and Cell Biology, Columbia University, New York, NY 10032, USA
    Cell 151:440-54. 2012
    ..These findings directly link defective splicing of critical neuronal genes induced by SMN deficiency to motor circuit dysfunction, establishing a molecular framework for the selective pathology of SMA...
  5. pmc The DcpS inhibitor RG3039 improves motor function in SMA mice
    James P Van Meerbeke
    These authors contributed equally to this study
    Hum Mol Genet 22:4074-83. 2013
    ....
  6. pmc A cell system for phenotypic screening of modifiers of SMN2 gene expression and function
    Darrick K Li
    Center for Motor Neuron Biology and Disease, Columbia University, New York, New York, United States of America
    PLoS ONE 8:e71965. 2013
    ....
  7. pmc SMN is essential for the biogenesis of U7 small nuclear ribonucleoprotein and 3'-end formation of histone mRNAs
    Sarah Tisdale
    Center for Motor Neuron Biology and Disease, Columbia University, New York, NY 10032, USA Department of Pathology and Cell Biology, Columbia University, New York, NY 10032, USA
    Cell Rep 5:1187-95. 2013
    ..These findings demonstrate that SMN is essential for U7 biogenesis and histone mRNA processing in vivo and identify an additional RNA pathway disrupted in SMA...
  8. ncbi SMN control of RNP assembly: from post-transcriptional gene regulation to motor neuron disease
    Darrick K Li
    Center for Motor Neuron Biology and Disease, Columbia University, New York, NY 10032, USA Department of Pathology and Cell Biology, Columbia University, New York, NY 10032, USA
    Semin Cell Dev Biol 32:22-9. 2014
    ..We discuss advances in our understanding of SMN activity as a chaperone of RNPs and how disruption of SMN-dependent RNA pathways can cause motor neuron disease. ..

Research Grants30

  1. Defining the Role of TDP-43 in Neurodegenerative Disease Pathways
    IGA NATALIA WEGORZEWSKA; Fiscal Year: 2013
    ..Additionally, we will examine whether abnormalities in RNA processing plays a fundamental role in TDP-43 related ALS, in an effort to define new targets for therapeutic intervention in ALS. ..
  2. Role of Stasimon Dysfunction in Spinal Muscular Atrophy
    Livio Pellizzoni; Fiscal Year: 2013
    ..Collectively, these experiments have the potential to identify Stasimon as a downstream target of SMN dysfunction that contributes to SMA pathology in a mouse model of this devastating human disease. ..
  3. Function of the Zinc Finger Protein ZPR1 in neurodegeneration
    LAXMAN DASS GANGWANI; Fiscal Year: 2013
    ..Identification of ZPR1 as protective modifier of SMA will allow development of novel strategies for the treatment of SMA. ..
  4. The Role of Alternative Splicing Factor Sfrs10 in Neural Development
    Rahul N Kanadia; Fiscal Year: 2013
    ..Extenstion of this work in my laboratory will provide me with preliminary data that 1 intend to use for an ROl grant that should launch my independent career in science. ..
  5. Molecular Mechanisms linking Aging, Abeta Proteotoxicity and Neurodegeneration
    Jeffery W Kelly; Fiscal Year: 2013
    ..abstract_text> ..
  6. Targeting SMN2 Alternative Splicing for the Treatment of Spinal Muscular Atrophy
    Michelle L Hastings; Fiscal Year: 2013
    ..This class of drug is relatively safe and would be an ideal therapeutic for the treatment of disease. ..