Transcript Presentation Slides

Understanding the impact of Schizophrenia
and Autism risk genes on brain development
Karun K. Singh, Ph.D.
Stem Cell and Cancer Research Institute
Department of Biochemistry and Biomedical Sciences
McMaster University
`
Genes and Neurodevelopment
Normal Brain Development
Brain Development Disorder
SCHIZOPHRENIA
Genetic Mutation
AUTISM
Symptoms of` Schizophrenia
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•
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Positive symptoms
– Hallucinations
– Delusions
– Thought disorder (confused thinking and speech)
Negative symptoms
– Diminished emotional expression
– Diminished motivation
– Inability to experience pleasure
Cognitive symptoms
– Poor concentration
– Difficult to plan and organize
– Poor memory
• Treatments
– Antipsychotic drugs (old and new
generation)
– Cognitive behavior therapy
Neuropathology` of Schizophrenia
N Eng J Med. 1990.
Unaffected twin
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•
•
•
Schizophrenic twin
Reduction of brain volume (Grey Matter)
Lateral Ventricle enlargement
Decreased GABAergic interneurons (GABA and GAD67 staining)
Less extensive arborization/neuronal complexity (dendritic/synapse)
• OVERALL – Nothing absolutely conclusive from brain imaging
Genetics plays a` major role in
psychiatric disorders
**Complex genetics at play in psychiatric disorders**
(Tom Insel, Director NIMH, JCI, 2010)
2011
Loci for SZ
• Exome Sequencing
• Whole Genome Sequencing
…more and more genes!
mir137
CSMD1
TRIM26
PCGEM1
Loci for BPD
ITIH3-ITIH4
region
Modeling the Genetics of
Neurodevelopmental
`
and Psychiatric Disorders
Brain Disease
Risk Gene
Developing
Mouse Brain
Patient Cells
Human Cellular
Reprogramming
Why do this?
1. Understand how genes impact brain structure/function during development
2. Understand core signaling pathways affected
Disrupted in Schizophrenia-1 (DISC1)
Chromosome (1; 11) translocation
disrupts the DISC1 locus.
Experimental model to` examine DISC1/Dixdc1:
The developing mouse cortex
Direction of migration
Approach: In utero electroporation to study neural stem
cells and neuronal differentiation/maturation
CP - neurons
IZ – axon tracts
VZ – neural stem cells
Dixdc1 functionally interacts
with DISC1 to
`
regulate neural progenitor proliferation
Singh et al., 2010
`
Dixdc1 and DISC1 regulate
neuronal migration
DISC1 Frag2
X DIXDC1
Singh et al., 2010
Dixdc1 is a critical regulator
of DISC1 and
`
embryonic brain development
Early brain development
Mid-brain development
Singh et al., 2010
Does Dixdc1 functionally
interact with DISC1 in
`
neural connectivity development?
• Dendrite Growth
• Spine Structure
• Synapse Formation
Penzes et al., Nat Neurosci 2011
Does a DISC1-Dixdc1 `pathway regulate the
growth of dendrites and synapses?
Control shRNA
DISC1 shRNA
Dixdc1 shRNA
Dixdc1 Frag2
DIV6
1000
900
800
700
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0
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10
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Ctrl shRNA
6
Disc1 shRNA
4
Dixdc1 shRNA
2
Dix Frag2
0
10
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Total Branch Length (µm)
Total Dendrite Branch Length
Number of Intersections
Sholl Analysis
Distance from Soma (μm)
Confirming this in vivo  in utero electroporation
Vickie Kwan, preliminary results
Examining synapses with genetic tools:
`
Trans-synaptic labeling using Rabies virus
Advantages
1. Single Cell
Resolution
2. Watch dynamics
over time
Ed Callaway Lab
Salk Institute
Trans-synaptic labeling in` mouse cortical neurons
IUE E15
LV-Syn-HTG
Culture E17
DIV 10
Infect:
Rabies
DIV 14
Fix cells
How does DISC/Dixdc1 regulate synapse formation?
Rabies virus courtesy of Ian
Wickersham and Heather
Sullivan (Seung Lab@MIT)
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Studying the Genetics
of Autism
Not included:
• Additional CNVs
• Exome sequencing
(de novo mutations)
• Whole genome
sequencing
Aldinger et al., 2011 Neuron
Human cellular reprogramming to create
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patient-derived neural cells
Advantages
• Model autism genes
• Behavior assays
• Neural circuits and
cell types involved
Some Disadvantages
• Difficult to model disease
gene networks, large CNVs,
human SNPs
• Gene disruption doesn’t
completely mimic human
genetics (eg. KO≠mutation)
• Not patient brain tissue
(human brain specific)
Human cellular reprogramming to create
`
patient-derived neural cells
Induced pluripotent
stem (iPS) cells
Direct conversion
patient skin
samples
Induced Neuronal (iN) or
Neural Progenitor (iNP) cells
Patient-derived
NEURAL CELLS
ADVANTAGES of Direct Conversion:
1. Faster than iPS method
2. Epigenetic signature of patient cell is likely preserved
3. Specific Neuronal subtype generation (Spinal Motor, Dopaminergic)
`
Studying the Genetics
of Autism
Aldinger et al., 2011 Neuron
Tuberous Sclerosis Complex (TSC): a genetic
`
disorder with high rates of autism
Collaboration with Dr. Philippe Major, Sainte-Justine Hospital, Montreal
1. Benign tumors in vital organs including brain
2. Autism features (syndromic autism) 25-60% in ASD
3. Learning disabilities, developmental delay
4. Epilepsy
Mouse Models
• Protein
Translation
• Plasticity
(mGluR-LTD)
Kelleher, III and Bear, 2012 CELL
Using Cellular Reprogramming to Study
`
TSC and Autism
Healthy or
TSC
Fibroblasts
Human
Neural
Cells
Synapse Function
Dendrite/Spine Growth
Trans-synaptic labeling
Automated Electrophysiology
Drug
Screen
In vivo Human Neuronal
Model
`
using Xenotransplantation
Patient-derived
neural cells
Fluorescent Label
Transplant
In vivo profile of human cells:
• How do patient neural cells functionally integrate into the developing
or adult brain?
Acknowledgements
My lab:
Vickie Kwan
Shashwat Desai
Omar Shehab
Massachusetts Institute
of Technology:
Dr. Li-Huei Tsai
University of MontrealSainte Justine Hospital
Dr. Philippe Major (TSC)
Funding:
Ontario Research Fund