WEEK 1 Flashcards
(34 cards)
What are neural stem cells?
(NSCs) are:
- undifferentiated cells
Defined by their capacity for:
- self-renewal
- multipotency
They are the source of all neuron types in CNS and PNS
During central nervous system development, NSCs proliferate and divide to generate clonally related progeny that differentiate into:
- neurons
- astrocytes
- oligodendrocytes
What are totipotent cells?
- 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)
When are produced more totipotent cells?
During the first few cell divisions in embryonic development
When do totipotent cells begin to specialise into pluripotent cells?
After four days of embryonic cell division
What are pluripotent cells?
- 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
As these pluripotent stem cells continue to divide, they begin to specialise further, what is their new name?
Multipotent stem cells
What are multipotent stem cells?
- 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
What are neuroepithelial cells?
The most primitive form of neural stem cells from the neural tube
In what neuroepithelial cells transition in the cortex ?
Neuroepithelial cells transition into:
radial glial cells
Which then give rise to neuronal progenitors:
- neurons
- astrocytes
- oligodendrocytes
Once the development has ended where can we find NSC populations?
NSCs are rare but can be find:
- dentate gyrus of the hippocampus
- subventricular zone of the lateral ventricle
What are Sox genes?
Sox genes such as Sox2 are among the earliest genes expressed ubiquitously in the early neural plate
- used as NSC markers
Examples of later neural stem cell markers
- intermediate filament protein Nestin
- RNA-binding protein Musashi
both:
- appear after Sox2 protein
- persist during embryonic development, and in adult neural stem cells
Where Sox2, Nestin and Musashi can be expressed?
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.
How to identify dividing cells?
- injecting systemically bromodeoxyuridine or BrdU,
(analogue of thymidine, that will intercalate in the DNA as it replicates)
= quantitative: injected systemically - using a retrovirus engineered to express green fluorescent protein (GFP)
= qualitative: injected locally; labelling the entire cells and its processes.
When can we derive NSCs and from which parts?
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
What are the other sources considered to derive NSCs?
NSCs can be generated from:
- non-neural multipotent stem cells.
e. g.
- bone marrow-derived mesenchymal stem cells
- haematopoietic stem cells
- Adipose stem cells
NSCs self-renewal and differentiation is regulated by:
- a precise temporal sequence of growth factor presentation
- intracellular signalling
- transcription factor expression
What are the three different stage of development where stem/progenitor cells can be collected?
- 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)
What are the two main shortcomings of using patient-specific IPS?
- 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
How to overcome patient-specific IPS problems?
- 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
What does CRISPR stand for?
Clustered Regularly Interspaced Short Palindromic Repeats
What does it refer to?
- 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
What it the most commonly used nuclease in research?
Cas9
- from the bacterium streptococcus
