FY2012 Annual Report

Formation and Regulation of Neuronal Connectivity Research Unit

Visiting Professor David Van Vactor



The mechanisms that refine and maintain synaptic connections are of central importance to the function of neural circuits.  The Van Vactor unit employs the powerful genetic system Drosophila to study highly conserved pathways controlling synapse development and synapse dysfunction.  We focus on the very well characterized neuromuscular junction (NMJ), an excitatory glutamatergic synapse that is accessible to many levels of analysis, and which has been used to map an extensive array of effector genes, from core components of neurotransmission, to trans-synaptic signaling cascades, to regulators that tune the deployment of these genes.  Our current work is on two areas: (i) a Spinal Muscular Atrophy (SMA) neurodegenerative disease model where loss of the Survival of motor neurons (Smn) gene causes retraction of motor neuron terminals, abnormalities in synapse structure/function, and death, and (ii) posttranscriptional regulation of synapse development by microRNAs that control the expression of downstream target mRNAs.

1. Staff

  • Dr. David Van Vactor, Professor
  • Dr. Takakazu Yokokura, Group Leader
  • Cecilia Lu, Research Scientist
  • Tamar Chobanyan, Research Technician ( - October, 2012)
  • Alex Edwards, Research Technician (November, 2012 -)
  • Shino Fibbs, Research Administrator

2. Collaborations

  • Theme: Computational analysis of RNA splicing patterns in high-content RNAseq datasets, and conservation of RNA splicing and stability effects from Drosophila to human models of Spinal Muscular Atrophy (SMA).
    • Type of collaboration: Joint research
    • Researchers:
      • Dr. Margarida Gama-Carvalho (University of Lisbon, Lisbon, Portugal)
  • Theme: Defining patterns of RNA splicing and stability characteristic of human IPS-derived mixed motor neuron model of Spinal Muscular Atrophy (SMA).
    • Type of collaboration: Joint research
    • Researchers:
      • Dr. Lee Rubin (Dept. of Stem Cell and Regenerative Biology, Harvard University, Boston, MA, USA)

3. Activities and Findings

A dominant hypothesis in the SMA field is that reduction in snRNP function due to loss of Smn activity is the principle cause of cellular and developmental pathology in SMA.  However, this has been controversial, and has not been thoroughly tested.  Over the past year, our unit has used high content RNA sequencing to map out the neural transcriptome-level patterns of gene expression in different SMA models.  First, using wild type and Smn disease models in fly, we have established a method of RNAseq data quality control in collaboration with Dr. Margarida Gama-Carvahlo, an expert in the mRNA splicing field (publication in preparation).  After multiple rounds of optimization, we have then generated sequence data sets to define the major genes altered by loss of Smn in Drosophila neurons.  Preliminary analysis reveals that thousands of transcripts change in stead state levels in Smn mutants.  With materials obtained from our collaborator Dr. Lee Rubin, we then generated RNAseq data sets for human patient-derived mixed motor neuron cultures.  Importantly, there is significant conservation overlap between the genes with altered expression in human and fly, and these conserved genes also overlap with our recent genetic screening results to define an SMA interactome with the fly model.  Unfortunately, methods for RNA splicing analysis that have been developed for human genome/transcriptome data are not effective with compact genomes like Drosophila or C. elegans.  Thus, we are extending our collaboration to develop improved alogrithms that will enable a comparison of SMA-dependent splice isoforms and an analysis to determine the degree of RNA splice pattern conservation from fly to human.

Our previous research on microRNA (miRNA) regulation of NMJ development revealed that the highly conserved miR-8 gene is required to promote synapse morphogenesis in late larval development through a largely postsynaptic mechanism.  Since this work, we also found that miR-8 is required for an early phase of synaptic targeting refinement in embryogenesis in a manner involving both presynaptic motor neurons and their postsynaptic muscle target cells.  A combination of proteomics and genomics identified two synaptic cell adhesion molecules as downstream effectors of miR-8 in this yearly phase of development.  However, these two CAMs are not direct mRNA targets for miR-8, thus raising the key question of how miR-8 activity is linked to their expression in the NMJ system.  Through bioinformatics, sensor experiments, and in vivo expression analysis in wild type and mutant tissues, we now have a highly conserved candidate transcription factor that is likely to mediate this link.  Experiments will soon determine the relative importance of this factor for presynaptic and postsynaptic development.

4. Publications

4.1 Journals

Nothing to report

4.2 Books and other one-time publications

Nothing to report

4.3 Oral and Poster Presentations

  1. Van Vactor, D., History of Developmental Biology, Developmental Neurobiology Course 2012, Okinawa, Japan, July 17, 2012
  2. Van Vactor, D., Neuronal Cell Biology, Signaling and Growth Cone Cytoskeleton, Developmental Neurobiology Course 2012, Okinawa, Japan, July 20, 2012
  3. Yokokura, T.,  Modeling Spinal Muscular Atrophy in Drosophila, 24th Takato Symposium, Nagano, Japan, Aug 23-24, 2012
  4. Yokokura, T., Smn, whose mutations cause Spinal Muscular Atrophy, regulates FGF signaling output, 35th Annual Meeting of the Molecular biology Society of Japan, Fukuoka, Japan, December 11 - 14, 2012
  5. Cecilia, L., Genetic Analysis of Neuromuscular Synapse Formation, OIST Internal Seminar, Okinawa, Japan, Feb. 15, 2013

5. Intellectual Property Rights and Other Specific Achievements

Nothing to report

6. Meetings and Events

6.1 Deveopmental Neurobiology Course 2012

  • Date: July 16-30, 2012
  • Venue: Seaside House/OIST Campus
  • Organizers: Drs. David Van Vactor, Ichiro Masai, and Mary Ann Price
  • Speakers:
    - Arturo Alvarez-Buylla, Principal Investigator, Brain Tumor Research Center, Dept. of Neurological Surgery School of Medicine, University of California San Francisco
    - Matthew Dalva, Associate Professor, Dept. of Neuroscience, Thomas Jefferson University
    - Leslie Clair Griffith, Professor of Biology, Brandeis University
    - Anne Hart, Professor, Dept. of Neuroscience, Brown University
    - Mary Hatten, Professor, Laboratory of Developmental Neurobiology, The Rockfeller University
    - Alex Kolodkin, Professor, The Solomon H. Snyder Dept. of Neuroscience, Johns Hopkins Univeristy School of Medicine
    - Carol Mason, Professor, Dept. of Pathology and Cell Biology, Columbia University
    - Susan McConnell, Professor, Dept. of Biology, Stanford University
    - Adrian Moore, Team Leader, Genetic Control of Neuronal Architecture, RIKEN Brain Science Institute
    - Stephen Smith, Professor, Dept. of Molecular and Cellular Physiology, Stanford University School of Medicine
    - Akinao Nose, Professor, Dept. of Complexity Science and Engineering, Graduate School of Frontier Sciences, The University of Tokyo
    - Pierre VAnderhaeghen, Senior Scientist, Institute of Interdisciplinary Research, University of Brussels
    - Jennifer Waters, Director of Microscopy, Nikon Imaging Center, Harvard Medical School
    - Ryohei Yasuda, Scientific Director, Max Planck Florida Institute
    - Junying Yuan, Professor, Dept. of Cell Biology, Harvard Medical School