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Year 4 - Neuroscience and Mental Health BSc > Stem Cells and Human Neurogenesis > Flashcards

Stem Cells and Human Neurogenesis Flashcards

1
Q

Define stem cells

A

2 important properties

  • Differentiation gives rise to specialised cell types
  • Self-renewal means stem cells can give rise to daughter cells equivalent to the parent cell
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2
Q

Describe cell potency

A
  • Range of commitment options available to a cell (how many cells can they generate?)
  • Totipotent (capacity to form an entire organism eg. zygote)
  • Pluripotent (able to form all cell lineages, including germ cells - ectoderm, mesoderm, endoderm)
  • Multipotent (can generate multiple cell types that constitute to an entire tissue or tissues - blood cells)
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3
Q

Describe embryonic germ layers

A
  • Zygote divides into a blastocyst.
  • At blastocyst stage divides
  • In gastrulation the inner cell mass forms the endoderm, mesoderm and ectoderm with some germ cells
  • Ectoderm: neural and skin
  • Mesoderm: Bone muscle blood cells
  • Endoderm: liver pancreas lung
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4
Q

How are stem cells categorised

A
  • Self renewal requirements
  • Differentiation potency
  • Where they come from

Types:

  • Pluripotent stem cells
  • Somatic (adult/tissue specific, also exist in embryois)
  • Cancer stem cells (not a physiological stem cell)
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5
Q

Describe pluripotent stem cells

A
  • Self renewal is unlimited
  • Derived from inner cell mass of embryos (embryonic stem cells - only from culture dish, as can self renew and have pluripotency)
  • Somatic human cell types eg. skin (reprogrammed to induce PSCs) - induced
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6
Q

Describe regulation of self renewal in PSCs

A
  • Intrinsic factors (Oct4, sox2 and nanog - form transcriptional network and regulate gene expression)
  • Extrinsic factors (growth factors, ECM, affect expression of intrinsic factors)
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7
Q

How do we assess for pluripotency?

A
  • Embroid body formation should create 3 germ layers (endoderm, mesoderm, ectoderm)
  • Teratoma formation (inject cells with cancer to form teratoma. The teratoma should contain tissue from all 3 layers)
  • Chimera formation (mouse pluripotent stem cells into a blastocyst, transplant resulting embryos into a mouse the same as the blastocyst donor. If the cell is pluripotent there should be chimeric colour)
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8
Q

Describe somatic stem cells

A
  • Neural, skin, blood (bone marrow), intestinal (bottom of crypts)
  • Replace injured or damaged cells in our body
  • In the brain: subventricular zone and subgranular zone
  • Limited self renewal, as they are niche dependent. They are capable of life long self renewal.
  • Lower plasticity and will not form teratoma.
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9
Q

Describe stem cell niche

A
  • Microenvironment that surrounds and nurtures stem cells and enables them to maintain tissue homeostasis
  • Neural: cellular elements (astrocytes, endothelial cells, ependymal) and molecular factors (eg. GF, ECM, CSF)
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10
Q

Describe multipotent stem cells

A
  • Can form all the cell types within one system

- Eg. neural stem cells can make neurons, astrocytes and microglia

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11
Q

Where do pluripotent cells exist?

A
  • In our body
  • All germ cells in our body are pluripotent
  • Also in culture
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12
Q

Why are PSCs best for neuroscience research?

A
  • Limited accessibility of brain tissues, particularly for studying human brain
  • Limitation of plasticity of neural stem cells
  • Difficulty in creating stem cell niche for neural stem cells in vitro to maintain their self renewal
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13
Q

List uses of PSCs in biological research

A
  • An in vitro model for studying embryonic development (brain development/neurogenesis)
  • A valuable cell model to elucidate molecular mechanisms underlying stem cell differentiation/self-renewal and diseases
  • A model to study function of specific genes in vitro and in vivo (mouse ES cells) through genetic manipulation
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14
Q

Compare embryonic development of mice and humans

A
  • Preimplantation stage human and mice look very similar.
  • However, after implantation the mouse has a very different structure to human
  • Mouse has a cylindrical shape, and human a disc like shape
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15
Q

Compare human and mice brain

A
  • Human brain is 1500g with 86 billion neurons, amnd mouse only 0.4g with 70 million neurons
  • Human brain has many sulci and gyri, while mouse brain has much less
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16
Q

Describe neural differentiation from PSCs

A

Must inhibit BMP as this inhibits pluripotency

17
Q

List uses of PSCs in medicine

A
  • Disease modelling (take patients primary cell, make iPSCs and then look for genetic cause, can then test drugs)
  • Drug discovery (could also take hESC and manipulate for gene defect then test with drugs)
  • Cell therapy
18
Q

Describe cell replacement therapy

A
  • Injecting or implanting live cells into a patient, to replace damaged or died cells for the recover of proper physiological functions
19
Q

List challenges for using PSC for cell replacement therapy

A
  • Differentiation of specific cell types
  • Integration and survival (will form teratoma)
  • Immune rejection
  • Tumorigenesis
20
Q

List possible methods to prevent tumorigenesis

A
  • Generation of iPSCs without changing genomic DNA using small molecules, RNAs and proteins
  • Optimal culture conditions to maintain genome stability
  • Eliminate undifferentiated cells before transplantation
  • Genetic modification of hPSC to prevent tumour formation (toxic ablation - integrate potential toxic gene, administer an inducer and the toxic protein is activated then cells will be killed)
21
Q

Define neural induction

A
  • Induction is a developmental mechanism:
  • One tissue secrets signalling factors that instruct an abutting (neighbouring) tissue
    to differentiate to a new cell fate
  • Organiser secretes neural inducing signals capable of organising the surrounding cells into the brain and head (eg. hensens node in chicks)
22
Q

Where is the mammalian node?

A
  • At the gastrulation front

- The gastrulation primitive streak formation generates 3 new layers (2nd week in human)

23
Q

Describe the 3 germ layers

A

Mesoderm:

  • PS derived layer of cells migrates adjacent to the epiblast.
  • It gives rise to the mesenchyme; and organs: spleen, kidney, gonads, heart, blood vessels and blood. It also gives rise to paraxial mesoderm: somites which are transient structure containing the precursors of muscle and skeleton of the trunk portion of the body

Definitive Endoderm

  • PS derived layer forming on top of the mesoderm. There it displaces/replaces the external epithelial layer (extraembryonic epithelium) “visceral endoderm” which surrounds the epiblast prior to gastrulation.
  • The endoderm gives rise to the gastrointestinal tract and organs: liver, pancreas, stomach, gut and lungs

Ectoderm:

  • Forms by conversion of the epiblast cells that do not ingress through the PS and will give rise to neuroectoderm and epidermis.
  • This neuroectoderm will form only the brain, which will also give rise to the craniofacial muscle and bone of the head
24
Q

List tissues that divide form the primitive node

A
  • Anterior endoderm
  • Node
  • Node derived notochord and prechordial plate
  • Loss of node in mouse embryos causes no brain, no notochord but there is a spinal cord
25
Q

Which signals induce brain formation?

A
  • Antagonists of primitive streak signals
26
Q

Summarise brain development

A
  • Brain forms on the “ectoderm” that consists of epiblast cells which do not ingress into the Primitive Streak (PS)
  • Brain is induced by signals emanating from tissues derived from the Anterior-PS (mammalian equivalent to Spemann Organiser):
  • The Anterior Endoderm (AE) and
  • The Node and the mesendoderm (notochord & prechordal plate)
  • The AE signals are Antagonists of the signalling pathways: BMP, NODAL and WNT
  • The brain grows inside out, from the ventricular zone to the pia surface
27
Q

Describe spinal cord development

A
  • The primitive Streak (PS) generates Mesoderm and Endoderm, but recently it has been shown that the PS mesoderm behind the Node generates neuromesodermal (NMPs) precursors
  • Neuromesoderm gives rise to the somites: two rows of condensed structures, which are separated by the node-derived mesendoderm and the neural tissue (neural plate) above the somites that will form the spinal cord neural plate
  • WNT and FGF Signals together generate NMPs
  • Then FGF alone differentiate NMPs to neuronal precursors; then + Retinoic Acid => spinal cord
  • While WNT alone convert the NMPs to somites
28
Q

Where does the PNS develop from?

A

Neural crest cells

29
Q

List examples of neurocristopathies

A
  • Goldenhar syndrome

- Waardenburg syndrome

Year 4 - Neuroscience and Mental Health BSc (23 decks)

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