HMB200 - Studying Intelligence

• HMB200 Final Exam Notes

Studying Intelligence

• Genetic roots of intelligence are explored through twin studies
• Common genetic variants like APOE may play a role
• Traditional methods, Genome-Wide Association Studies, and Fusion Approaches are utilized in studying intelligence

Intelligence Genes & Methods

• Method 1 (Traditional): Candidate genes, SNPs and IQ association (test) are examined
• Candidate genes examples: KNCMA1, NRXN1, POU2F3, SCRT and genes related to Glutamate neurotransmission | synaptic plasticity - learning & memory
• Method 1 is limited by small sample sizes
• Method 2 (Genome Wide Association Study): Tens of thousands of SNPs are analyzed at once, with a stringent statistical threshold (5x10-8)
• Method 2 utilizes IQ association tests, but its effectiveness is limited
• Method 3 (Fusion Approach): Features Alternative 2-stage methods (1 & 2), Proxy phenotype (i.e. education), small SNP sets, and candidate identification

Biological Approach to Brain Research

• Neuroethology is used to compare different brains
• Forebrain engraftment involves transplanting brain tissue
• Human astrocytes exhibit variability in composition, size, complexity, morphology, and function, enabling rapid and diverse Ca2+ syncytium signals
• Control signal transmission is a key aspect of astrocyte function
• Chimeric or humanized mouse brains are utilized as models

Utilizing Chimeric Brain Models

• Chimeric brain models involve using human astrocytes in animal models
• Glial progenitors (GPCs) are isolated
• Lineage: Markers used are APC (A2B5+) and PSA-NCAM-
• Embryonic forebrain tissue is used
• Dissociated cell cultures are prepared
• Microscopy techniques for cell sorting
• Infect cells w/ VSG lentiviral vector w/ GFP
• Xenografts are used to observe cell differentiation
• Neonatal Rag2 null mice are used; they lack an immune system
• GFP expression is monitored for up to one year
• Examining tissue sections with stains
• Human nuclei (hNuclei) are identified using human nuclear antigen
• Observations are focused on the hippocampus and cortex
• Radial glial cells transition from uncommitted to committed progenitors, eventually becoming astrocytes
• GRP: These glial restricted progenitors, can also differentiate into oligodendrocytes
• APC is used as an astrocytic progenitor cell marker. Identified by A2B5+ cell surface, NOT PSA-NCAM-

Confirming Human Brain Cell Integration

• Microscopy and specific markers are used
• Analyses are performed at 5 months in the corpus callosum (cortical layer V, VI)
• Analyses are performed at 11 months in the full cortex
• Analyses are performed at 14 months in the hippocampus and dentate gyrus (DG)
• Human cells in mice exhibit:
  • Larger size
  • End-feet/processes at the blood vessels (BV)
  • Tortuous/long structures (> 600µm)
  • Interlaminar positioning (only in adult humans, apes)
• Patch pipette electrophysiology techniques are used
• Rhod2 is added as a marker
• Diffusion is observed in human mice through network and gap junctions
• Identification of syncytium and astrocyte coupling

Astrocytes, IQ, and Long-Term Potentiation

• Glutamate and GABA metabotropic receptors participate
• More Calcium (Ca2+) is present within cells
• Change synaptic plasticity through Long-Term Potentiation (LTP)
• Good LTP is related to good learning and memory

Long-Term Potentiation & Assessment

• LTP is more effective in chimeric/xenograft models compared to allografts and controls
• Studies use chimeric and null mice to evaluate how learning behaviour is affected
• Fear (amygdala) is tested
• Spatial learning is tested in Barnes Mazes
• Novel recognition is tested

Human vs Thalidomide Effects

• Human cells show More TNFa and More LTP
• Thalidomide causes birth defects, crosses the blood-brain barrier (BBB), inhibits TNFa and LTP
• Implanting human cells back to mouse can model effects of drugs

Schizophrenia Overview

• Schizophrenia affects 1% of the global population and is heritable
• High costs are associated with morbidity, mortality, and sex differences
• Less grey matter, white matter, and hypomyelination in the brain
• Metabolic disorders (diabetes, dyslipidemia), premature aging (cancer), infections, and CVD contribute as natural causes
• Access to resources, stigma, unemployment, and homelessness are identified as mediating factors
• Suicide, homicide, and accidents are listed as unnatural causes

Categorizing Schizophrenia Symptoms

• Negative symptoms of schizophrenia include anhedonia, affective flattening, asocial behavior, avolition, and alogia
• Positive symptoms include hallucinations, bizarre behavior, messy speech, catatonia, and inappropriate affect
• Cognitive impairments includes in attention, memory, learning, reasoning, and mistrust

Stages and Onset of Schizophrenia

• Premorbid stage: Characterized by few or no symptoms
• Prodromal stage: Attenuated symptoms are present
• Syndromal stage: Psychotic deterioration occurs
• Chronic or residual stage: Psychotic, negative, cognitive, and functional symptoms persist
• Onset in aging includes:
  • Old-old age (over 75 years):
  • Young-old age (55+):
  • Improved positive symptoms
  • Cognitive decline with early aging
  • Reduced effectiveness of antipsychotics
• Onset in 20s is typically characterized by mood and personal disorders
  • Late teens or early 20s for males
  • Late 40s for females

Synaptic Dysfunction in Schizophrenia

• Excessive synaptic pruning
• Childhood/adolescence development
• Prefrontal cortex: C4, genetics, microglia
• C4 overexpression
• Less LTP, LTD
• Less dendritic spine density
• Less DISC1 and NRG1

Schizophrenia and Synapses

• Synaptic dysfunction is associated with Excess synaptic pruning during childhood/adolescence
• Involves prefrontal cortex, genetic studies reveal C4 overexpression, reducing Long-Term Potentiation (LTP) and Long-Term Depression (LTD)
• Affects dendritic spine density, and levels of DISC1 and NRG1

Dopamine and Hypofunctioning Glutamate

• Mesolimbic path, causing Hallucinations
• Deficit in prefrontal cortex, resulting in cognitive impairment
• Hypofunction of Glutamate, affecting transmission
• Reduced GABAeric signal and Imbalance disrupts the 'go/stop' mechanisms
• Affect motivation, motor skills. May cause addiction
• Amphetamine and LDOPA stimulate dopamine, potentially worsening the disease in some patients

Glial Cell Studies

• Targets glial genes
• Fewer oligodendrocytes reduce neuron support
• Investigates cells from juvenile-onset individuals and healthy control
• Lentivirus: polyscistronic vector delivers genes

Glia Experiment

• Reprogrammed with Oct4, Sox2, Klf4, and Myc factors
• Cells are introduced in vitro to become glia (astrocytes and oligodendrocytes)
• Neonatal mouse transplant are used Immunodeficient + Shiverer (Shi) (hypomyelin)
• Studying if more glial cells are helpful

Identifying Glial Lineage

• PGDRFa marks glial progenitor cells (GRPCs)
• GFAP markers for astrocytes
• S100B also marks astrocytes
• MBP marks for oligodendrocytes
• Stain cells (for Oct4) and check nuclear staining
• Conduct Teratoma assay on (SCID) mice to see layers and structures

Schizophrenia results

• Schizophrenia brains have less myelin, astrocytes, fewer processes, and less grey matter.

Myelin & Genes

• LINGO 1 impacts axon myelination, as do other oligo genes.

Oligodendrocytes & Proteins

CNS Specific Oligo OMgp Nogo MAG Neuron Part (complex) NgR P75 Lingo-1

Disrupting Signals

Alzheimers SCZ Depression Spinal Injury

Behavioural testing

• Testing in rodents tries to mimic human trends
• Domains can be Cognitive, Social or Related to Hallucinations
• Restore PPI with dopamine and glutamate. Induce with genes related to SCZ

SCZ Tests

Elevated Plus Maze for anxiety: SCZ mice less willing to explore open arm Y maze: SCZ mice less likely to alternate as much Novel Object Test: SCZ mice less likely to distinguish novel Social Interaction test:SCZ mice show less interest

ALS

• Disease impacts connection between nerve/muscle signaling

ALS CAUSES

• Glutamate released by neurons
• Damage comes from mitochondrial dysfunction
• Issues come from aggregation of proteins such as TDP-43/FUS

Transdifferentation

Reprogramming cells to other types (neurons). Has potential to repair brain.

• Use chemicals

• Forces cell down a chemical/transcription path

• Better due to not causing cancer

• Doesn't have to be native stem cells

• Can stimulate certain chemicals to cross BBB barrier

• Can target native resident reactive cells

• Can promote migration of cells or create cells

Viruses for delivery of cells

• Modify adeno viruses to not attack own
• Can't replicate themselves: stops infection
• Causes cells to trigger immune action

BBB Barriers? Trigger: Not an issue Brain: Cisterna magna

• Directly into blood vessel to cause migration/repair AAV2, AAV5 have been show to work

Depression

• Disregulated mood and motivation
• Causes: brain issue?

Mesenchyme Cells

• Can cause neurogenesis and synapse regulation
• Can stop microglia and apopotosis

Tests

• MSC cells shown to help with FST swim test
• Increase activity and lower stress hormones
• More Cfos in parts of brain relating to activation Increase neuroprotection and anti-inflammatory

Final slide

How to cross-check inconsistent data from RNAS Biological checks and functions Neurodegeneration markers ALS specific markers Dying back model/Dying forward model Why AAVs are important Considerations for AAVs An important brain structure – why?