Quiz 4 Neurosci

What is epigenetics?

Modifications “above” DNA that change gene expression without altering the DNA sequence

What do epigenetic “chemical tags” do?

Control whether genes are expressed and how much they are expressed

What are the two main epigenetic mechanisms?

DNA methylation and histone modification

What is DNA methylation?

Addition of methyl groups to cytosine bases in DNA that typically silences gene expression

What is histone modification?

Chemical changes to histone proteins that alter chromatin structure and gene transcription

Can the environment affect gene expression?

Yes, factors like diet, social interactions, and chemicals can change gene expression

Are epigenetic changes only during development?

No, they occur throughout life

What does epigenetics suggest about genetics?

We are not solely determined by our genes; environment plays a major role

How does maternal care affect offspring?

It alters gene expression and stress responses

What do high licking/grooming mothers produce in offspring?

More glucocorticoid receptors in the hippocampus

What is the effect of more glucocorticoid receptors?

More efficient stress response and better regulation of the HPA axis

What happens with low maternal care?

Fewer receptors, weaker stress regulation, and higher stress response

What hormone is involved in stress response?

Cortisol (a glucocorticoid)

What does chronic cortisol exposure do?

Inhibits neurogenesis and can kill hippocampal neurons

How does the hippocampus regulate stress?

Through negative feedback that shuts down stress hormone release

What is neurogenesis?

The process of generating new neurons from neural stem cells, important for brain function and plasticity.

What increases neurogenesis?

Exercise, learning (in some cases), and enriched environments

What decreases neurogenesis?

Stress and high cortisol levels

What is BDNF?

A growth factor that supports neuron survival and growth

What does exercise do for the brain?

Increases neurogenesis, BDNF, and blood vessel growth (angiogenesis)

What is environmental enrichment?

Stimulating environments with social interaction, exercise, and learning opportunities

What effect does environmental enrichment have?

Increases neuron production by about 60% in the hippocampus

What are nutrigenomic effects?

Effects of diet on gene expression and health outcomes

What is BPA?

A chemical that decreases DNA methylation and negatively affects gene expression

What can reverse BPA effects?

A methyl-rich diet (e.g., choline, folic acid, B12)

What are stem cells?

Cells that can self-renew and differentiate into other cell types

What are pluripotent stem cells?

Cells that can become any type of cell in the body

What are induced pluripotent stem cells (iPSCs)?

Mature cells reprogrammed into stem cells using specific genes

What are iPSCs used for?

Disease treatment, tissue regeneration, and disease modeling

When does neural development begin?

Around 18 days after conception (neural plate forms)

What is the neural tube?

Structure that develops into the brain and spinal cord

What are the three brain divisions formed?

Forebrain, midbrain, hindbrain

What are the stages of brain development?

1. Neurogenesis

2. Cell migration

3. Differentiation

4. Synaptogenesis

5. (plus regressive events like pruning)

What is synaptogenesis?

Formation of synaptic connections between neurons

what is cell migration?

Movement of neurons from their origin to their final position in the brain.

what is differentiation?

The process by which unspecialized cells develop into different types of neurons or glial cells, acquiring distinct functions and characteristics.

HOW does DNA methylation silence genes?

Prevents transcription factors from accessing DNA

HOW do histone modifications affect transcription?

They change chromatin structure, altering access of transcription machinery

Loosened = increased transcription

Tightened = decreased transcription

What is chromatin?

DNA wrapped around histone proteins

HOW does maternal care change gene expression?

Alters epigenetic tags on genes regulating stress response

What is the full causal chain for low maternal care?

Low care → epigenetic changes → fewer glucocorticoid receptors → weaker negative feedback → higher cortisol

WHY do glucocorticoid receptors matter?

They help shut off the stress response (negative feedback)

HOW does nutrition affect gene expression?

By altering epigenetic marks like DNA methylation

What is the key idea of nutrigenomics?

Diet can regulate gene expression and health outcomes

Why do identical twins become different over time?

Environmental differences lead to different epigenetic modifications

Where does adult neurogenesis occur?

Hippocampus, olfactory bulb, and some other areas

HOW do scientists identify new neurons?

Using BrdU. which labels dividing cells

WHY does exercise increase neurogenesis?

It increases BDNF. which promotes neuron growth and survival

What does BDNF do?

Supports existing neurons

Promotes new neuron growth

Enhances differentiation

What is the mechanism linking stress to reduced neurogenesis?

High glucocorticoids suppress neuron formation

List 3 factors that increase neurogenesis

Exercise, Enriched environment, hippocampal-dependent learning

What is an enriched environment?

A setting with social interaction, stimulation, and activity

What are the two key properties of stem cells?

Self-renewal and differentiation

Difference between pluripotent and multipotent stem cells?

Pluripotent → any cell type

Multipotent → limited to a lineage

HOW are induced pluripotent stem cells (iPSCs) created?

By inserting stem-cell genes into adult cells via viral transfection

WHY are iPSCs important?

• Patient-specific therapies

• Disease modeling (“diseases in a dish”)

What is a major limitation of iPSCs?

Viral methods can disrupt DNA and increase cancer risk

What is another limitation of iPSCs?

Cells may retain memory of original cell type

What happens at ~22 days?

Neural tube forms

What does the neural tube become?

Brain and spinal cord

Where are neurons first generated?

Ventricular zone

What are the stages of nervous system development?

1. Neurogenesis

2. Cell migration

3. Differentiation

4. Synaptogenesis

5. Synaptic rearrangement

6. Cell death

HOW do neurons migrate?

Guided by radial glial cells

HOW do neurons form connections?

Growth cones follow chemical signals to targets

WHY does neuronal cell death occur?

Competition for synaptic targets and neurotrophic factors

What is spina bifida?

Failure of neural tube to close at caudal end

What is anencephaly?

Failure of neural tube to close at rostral end

What determines genetic sex?

XX vs XY chromosomes

What does the SRY gene do?

Triggers testes development

What happens without SRY?

Ovaries develop

HOW do hormones influence development?

Gonadal hormones shape body and brain development

When is brain sex determined?

Before birth

What happens if glucocorticoid receptors are reduced?

Poor stress regulation → prolonged cortisol response

If stress is chronic, what happens to neurogenesis?

Decreases due to high glucocorticoids

If someone exercises regularly, what brain changes occur?

↑ BDNF, ↑ neurogenesis, ↑ neuron survival

Why is epigenetics important for behavior?

Environment can shape brain function and behavior via gene expression