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Contemporary advances in neuroscience > WEEK 1 > Flashcards

WEEK 1 Flashcards

1
Q

What are neural stem cells?

A

(NSCs) are:
- undifferentiated cells

Defined by their capacity for:

  • self-renewal
  • multipotency

They are the source of all neuron types in CNS and PNS

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2
Q

During central nervous system development, NSCs proliferate and divide to generate clonally related progeny that differentiate into:

A
  • neurons
  • astrocytes
  • oligodendrocytes
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3
Q

What are totipotent cells?

A
  • most versatile of stem cell type

Has the potential to give rise to:

  • any and all human cells (brain, liver, blood, heart cells)
  • an entire functional organism

e.g. fertilised egg (up to 4 days)

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4
Q

When are produced more totipotent cells?

A

During the first few cell divisions in embryonic development

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5
Q

When do totipotent cells begin to specialise into pluripotent cells?

A

After four days of embryonic cell division

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6
Q

What are pluripotent cells?

A
  • cells that can give rise to all tissue types
  • cannot give rise to an entire organism

e. g. inner cell mass layer of the blastocyst
e. g. induced pluripotent stem (IPS) cell

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7
Q

As these pluripotent stem cells continue to divide, they begin to specialise further, what is their new name?

A

Multipotent stem cells

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8
Q

What are multipotent stem cells?

A
  • less plastic stem cells
  • more differentiated stem cells
  • give rise to a limited range of cells within a tissue type

e.g. neural stem cells

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9
Q

What are neuroepithelial cells?

A

The most primitive form of neural stem cells from the neural tube

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10
Q

In what neuroepithelial cells transition in the cortex ?

A

Neuroepithelial cells transition into:
radial glial cells

Which then give rise to neuronal progenitors:

  • neurons
  • astrocytes
  • oligodendrocytes
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11
Q

Once the development has ended where can we find NSC populations?

A

NSCs are rare but can be find:

  • dentate gyrus of the hippocampus
  • subventricular zone of the lateral ventricle
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12
Q

What are Sox genes?

A

Sox genes such as Sox2 are among the earliest genes expressed ubiquitously in the early neural plate
- used as NSC markers

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13
Q

Examples of later neural stem cell markers

A
  • intermediate filament protein Nestin
  • RNA-binding protein Musashi

both:

  • appear after Sox2 protein
  • persist during embryonic development, and in adult neural stem cells
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14
Q

Where Sox2, Nestin and Musashi can be expressed?

A

In restricted progenitors, such as:

  • neuronal
  • glial-restricted progenitors

e.g. Sox2 is expressed in glial progenitor cells.

So, there’s no exclusive antigen that has been identified so far to label neural stem cells.

A combination of positive and negative markers are required to identify NSCs.

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15
Q

How to identify dividing cells?

A
  1. injecting systemically bromodeoxyuridine or BrdU,
    (analogue of thymidine, that will intercalate in the DNA as it replicates)
    = quantitative: injected systemically
  2. using a retrovirus engineered to express green fluorescent protein (GFP)
    = qualitative: injected locally; labelling the entire cells and its processes.
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16
Q

When can we derive NSCs and from which parts?

A

At any time:

  • during development starting with the blastocyst stage or the gastrula stage
  • during embryonic development

We can extract them from:

  • the neural plate (whether it’s early or later)
  • the adult brain
17
Q

What are the other sources considered to derive NSCs?

A

NSCs can be generated from:
- non-neural multipotent stem cells.

e. g.
- bone marrow-derived mesenchymal stem cells
- haematopoietic stem cells

  • Adipose stem cells
18
Q

NSCs self-renewal and differentiation is regulated by:

A
  • a precise temporal sequence of growth factor presentation
  • intracellular signalling
  • transcription factor expression
19
Q

What are the three different stage of development where stem/progenitor cells can be collected?

A
  • inner mass layer of the major blastocyst
  • foetus (brain, spinal cord, olfactory system or umbilical cord)
  • adult (brain, spinal cord, olfactory system, bone marrow, blood, skin)
20
Q

What are the two main shortcomings of using patient-specific IPS?

A
  • genetic abnormalities that arise in human individuals are not always clean can complicate the interpretation of experiments.
    e. g. small chromosomal abnormalities, which are thought to give rise to conditions such as autism and schizophrenia, often encompass more than one gene
  • normal genetic variability between human subjects means that cell lines need to be made from multiple individuals:
  • a particular disease of interest
  • unaffected individuals
    to have the power to detect subtle cellular differences that could be involved in the disease process
21
Q

How to overcome patient-specific IPS problems?

A
  • by engineering known disease-causing mutations into an IPS cell from an unaffected individual
    = allows a precise genetic change to be made, and the original cell line can be used as an isogenic control
22
Q

What does CRISPR stand for?

A

Clustered Regularly Interspaced Short Palindromic Repeats

23
Q

What does it refer to?

A
  • This name refers to the DNA sequences discovered in the genomes of bacteria.
  • These unusual DNA sequences were found to be part of a type of innate immunity that bacteria have developed against viruses
  • CRISPR sequences in the bacterial genome arise because when the bacterial cell is infected by a virus, the viral DNA is processed by the bacteria into short segments and integrated into the host bacteria’s genome
24
Q

What it the most commonly used nuclease in research?

A

Cas9

- from the bacterium streptococcus

25
Q

What is the PAM sequence for streptococcus Cas9?

A
  • NGG (N stands for any nucleotide)

= Follows on directly after the guide sequence. The PAM sequence is essential for binding of the CRISPR Cas9, but does not form parts of the guide sequence itself.

PAM sequence 
(PAM = rotospacer adjacent motif)
26
Q

What are the two examples of the types of genetic changes that can be introduced using CRISPR to facilitate the study of disease in human cells?

A
  • inactivating the function of a gene
  • altering a single base pair to make a point mutation.

These two types of genome edits can be made by taking advantage of two different repair pathways in the cell for fixing double-strand breaks in DNA.
= When a DNA strand undergoes a double-strand break, the cell typically uses one of two main pathways to repair it.

27
Q

What are the two repair pathways?

A
  • non-homologous end joining
    = the quickest and the most commonly used repair pathway in most cells, including pluripotent stem cells
    = this repair pathway is error-prone
  • homology-directed repair
    = uses a sister chromatid as a template to create a very accurate repair to the break.
    = only active in a cell just before cell division, because this is the only time a cell has a second copy of its DNA close by to use as a template
28
Q

What is the name of the process of degrading abnormal RNA transcripts?

A

Nonsense-mediated decay

29
Q

Define amyotrophic lateral sclerosis

A

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease.

Characterised by:

  • loss of motor neurons
  • progressive muscle wasting
  • death typically occurring within 3 to 5 years of symptom onset

Mutations in a number of different genes have been found to cause ALS. Many of these mutations, which affect genes such as:
- superoxide dismutase 1
- TAR DNA-binding protein 43
are single point mutations

Some of these mutations cause:
- loss in function,
or are thought to:
- give rise to a toxic gain-of-function,
such as in the formation of toxic protein aggregates

30
Q

What are the main advantages of using an adeno-associated virus (AAV)?

A
  • does not trigger a strong immune reaction in humans
  • this particular viral serotype (serotype 9) can cross the blood-brain barrier and efficiently infects neurons after systemic administration
31
Q

What is the rotarod test?

A

The rotarod performance test is a performance test based on a rotating rod with forced motor activity being applied, usually by a rodent. The test measures parameters such as riding time (seconds) or endurance. Some of the functions of the test include evaluating balance, grip strength and motor coordination of the subjects

32
Q

What is the micro satellite repeat expansions?

A

A type of genetic abnormality that leads to a number of different neurological diseases.

e. g.
- Huntington’s
- fragile X syndrome
- certain forms of motor neuron disease

  • These are repetitive 2 to 9 base pair (bp) sequences of DNA, often occurring in non-coding regions of protein coding genes.
  • These sequences do occur in healthy individuals but are found to be greatly expanded in length in affected individuals
33
Q

Cite an example of microsatellite repeat expansion that can give rise to both motor neuron disease and frontal temporal dementia.

A

Gene C9orf72
- Healthy individuals typically have between two and 23 repeats of the hexanucleotide sequence, GGGGCC (G4C2) in the first intron of the C9orf72 gene, whereas affected individuals may have many thousands of repeats of this sequence.

34
Q

What are the consequences of this repeat expansion?

A
  • affect the normal expression of the gene
  • produce a toxic gain of function due to abnormal translation of the repeat sequence, producing toxic dipeptide protein aggregates.

The presence of these sequences in non-coding regions means it is not possible to eliminate their toxic effects by knocking out the host gene, and their size makes homology-directed repair impractical

Contemporary advances in neuroscience (2 decks)

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