1

Question 1

how do you reprogram a cell

Answer 1

express genes found in embryos to induce pluripotent stem cells, they can generate every cell in the body.

Question 2

what is totipotent

Answer 2

zygote

it can make all tissues including the placenta.

Question 3

what is pluripotent and what is multipotent

Answer 3

pluri means everything but the placenta and includes germ cells

multi means more than one fate.

Question 4

when is the body axis built

when is embryonic organogenesis

Answer 4

0-3 weeks

3-8 weeks

Question 5

what are adult stem cells

what are gonadal germ cells

Answer 5

some cells are set aside in an undifferentiated state to contribute to the individual over its lifetime, they are multipotent.

another type of specialized cells are set aside in an undifferentiated state , for the next generation, they are specialised totipotent cells in the gonads and so the next generation is being built at the same time as the embryo.

Question 6

where do the gametes arise from

where do the gonads arise from

why are the gametes in the gonads

Answer 6

gonadal germ cells/primordial germ cells.

mesoderm and endoderm.

gametes dont arise from the gonads they migrate into them.

Question 7

how are the germ cells and somatic cells divided in different types of animals

Answer 7

in all plants and some animals, somatic cells can readily form new organisms.
in many animals there is an early division between the somatic and germ cells, insects and vertibrae.

Question 8

where do primordial germ cells come from and what do they do when they are determined

Answer 8

they are determined in a specific location on the edge of the embryo and they stay here as the body axis form for 0-3 weeks. they are protected here from the differenciation signals.
they arise from extra embryonic mesoendodermal cells
they migrate to the gonads and become progenitors for eggs and sperm.

Question 9

what do you need for germ cell determination

Answer 9

a plastic cell type

a cell capable of undergoing meiosis and not mitosis.

Question 10

what is the early development of the nematode like

Answer 10

starts as a single cell and you can follow each division as it develops.
in the early cleavages they are asymmetric, producing a specialized cell - P lineage cell.
when the P1 divides it will make a P2 cell and an EMS cell.
the P cell is always maintained at the posterior of the embryo.

Question 11

why is the cell division plane so crucial

Answer 11

the mothers determinants will all be on one side of the cell, so depending on whether the cell divides vertically or horizontally will determine the fate of the daughter cells.
the P cell arises this way, P cells inherit specialised P granules that are in the cytoplasm but can enter the nucleus, they are a mix of proteins and RNA.

Question 12

what do the P granules in the P cell do

Answer 12

they bind to the DNA of the P cell and block almost all transcription and because of this all differenciation.
they block translation in the cytoplasm
the transcription that remains promotes stem cell fate and causes cells to undergo meiosis instead of mitosis.

Question 13

What is in vertebrates that is similar to the P cell

Answer 13

they have a similar cell also in the posterior of the developing embryo.
it will express the transcription blocker nanos.
in all vertebrates in the very earliest stage of development a germ cell is established, this cell will show very little transcription or translation and no differenciation.
these cells are pluripotent and can undergo meiosis

Question 14

controlling widespread transcriptional decisions

Answer 14

primordial germ cells are shut down transcriptionally and translationally.
but what governs this widespread shut down
epigenetic silencing can be done by DNA methylation to repress gene activity.
or by histone modification to stop being able to access the genes because the DNA is wrapped so tightly around the histone.

Question 15

when do primordial germ cells migrate and what happens in drosophila

Answer 15

once the rapid differenciation of early embryogenesis begins to decrease at about eight weeks, they can begin to migrate into the embryo.
in drosophila they are called pole cells and they are transcribing a gene called vasa, so we can track them by tracking vasa.
the germ cells attach to and migrate through the gut until they reach the midgut and they migrate sideways towards the future gonads
here they are protected in a specialised microenvironment called the gonadal niche.

Question 16

what happens in drosophila when the primordial germ cells reach the gonads

Answer 16

when the pole cells reach the gonads they continue to divide through the larval stage and differenciate at metamorphosis.
they become eggs or sperm depending on whether the gonads are ovaries or testes.
in ovaries the cells attach to the stromal cap
in testes the cells attach to the hub cells

Question 17

what happens in vertebrates when the primordial germ cells migrate

Answer 17

the germ cells migrate through the posterior gut along a fibronectin tail
they leave the gut and move laterally to the genital ridges (derived from intermediate mesoderm) because of the release of a chemoattractant.
the are now in the protective niche that is the gonads.

Question 18

why do the gonads develop

Answer 18

because of the reciprocal communication between the germ cells and the genital ridges.

Question 19

how are the germ cells protected when they are travelling

Answer 19

the travelling stem cell niche- support cells that travel with the germ cells help to maintain the undifferenciated stem cell phenotype.
they secrete stem cell factor
a failure to migrate to the protective niche or to make SCF causes the formation of a teratoma because the cells differentiate.

Question 20

when the zygote divides what does it become

what does each part go on to form

where do embryonic stem cells come from

Answer 20

it divides to make a ball of cells and the cells on the inside will have a different fate to the outer cells (32 cells)
inner cells become the embryo and the outer trophectoderm becomes the placenta.
the inner cell mass cells can be removed and cultured and become embryonic stem cells, they are taken at the blastocyst stage.

Question 21

what happens in mitosis of stem cells

Answer 21

it gives rise to a daughter that is exactly the same as the mother (renewal)
and another cell that will become a differenciated cell.

Question 22

What do the daughters of stem cells that differentiate do

Answer 22

They replace dead or damaged cells.
Add new cells to increase organ size.
Generate cell types required at a specific time of life.

Question 23

Where were adult stem cells first found

Answer 23

They were first recognised in bone marrow, liver, gut and skin.

But they are found in most organs.

Question 24

What do these make:

Haematopoetic stem cells
Mesenchymal stem cells
Epithelial stem cells

Answer 24

Blood and immune system.

Bone, cartilage, fat, muscle, tendon and ligaments

Skin and gut.

Question 25

What are characteristics of stem cell niches. | And what happens inside them

Answer 25

They have a good portal capillary network and neurons so it can gain information from the body. The stem cells are anchored via complex cell adhesion molecules to support cells (stromal cells). The support cells release SCF, BMPs and jack stats. The stem cells communicate back when they differentiate to tell the other stem cells to stop dividing.

Question 26

How do satellite cells work

Answer 26

The cells sit just outside the muscle fibres under the muscle basal Lamina. Pax7 means the cell will self renew and myod means the cell will differentiate.

Question 27

Mesenchymal stem cells

Answer 27

Located thought the body in bone marrow and fat. Very multipotent - cartilage, muscle, fat, tendons, ligaments. Easy to isolate from cord blood.

Question 28

Epithelial stem cells

Answer 28

Each hair cell in the skin has a shaft with a bulge where skin stem cells are located. In the gut behind every villus is a crypt which contains stem cells.

Question 29

Neural stem cells How potent are they Where are they found

Answer 29

They have a radial glial morphology And they are bipotent so can become either neurons or glia. They can survive into adulthood. They are found in three regions of the brain: Subventricular zone lining the lateral ventricles, gives rise to newly born neurons that migrate to the olfactory bulb via the rostral migratory stream. Subgranular zone in the dentate gyrus of the hippocampus involved in new memories. Hypothalamus lining the third ventricles, where they contribute new neurons to energy and feedback circuits.

Question 30

What are the two ways of defining pluripotency at day 4 and 5 of development. What happens when pluripotent cells are grafted onto a mouse kidney.

Answer 30

The cells are pluripotent when the embryo is a blastocyst at day 4. Around day 5 the embryo implants in the uterus and start differentiating and keeps pluripotency. Teratocarcinoma

Question 31

What happens during gastrulation and what does it make

Answer 31

It happens at day 7 and is the onset of cell type specification. The ectoderm becomes the skin and neural. Mesoderm becomes blood, muscle, heart and kidney. Endoderm becomes the gut, internal organs, liver, pancreas. At the end of gastrulation the pluripotent cells become extinct.

Question 32

What do we need to do to grow stem cell populations in vitro. And how do we collect it from mice.

Answer 32

The niche should be mimicked in the Petri dish to keep the cells self renewing. In mice, leukaemia inhibitory factor and BMP is used and in humans FGF2 and TGFB are used. Take a mouse embryo at day four and dissociate the inner cell mass using an enzyme. Plate the cells on top of some other cells called feeders, these will provide the LIF and BMP.

Question 33

How do we make induced pluripotent stem cells.

Answer 33

Take a skin biopsy from a person and overexpress pluripotency factors in the cells. Now they are pluripotent and can self renew and differentiate.

Question 34

What genes do embryonic stem cells express

Answer 34

Pluripotency factors like oct4, nanog, sox2. | They don’t express any genes indicative of differentiation.

Question 35

How to make a culture of in vitro neural stem cells What do they express and what don’t they express. What if you take away the cytokines.

Answer 35

We can take a feral brain that contains endogenous neural stem cells, and dissociate the cells. Then plate them onto laminin in the presence of FGF2 and EGF to mimic the stem cell niche. Neural stem cells express RC2 which is a marker of non differentiation. They express no genes indicative of differentiation such as GFAP for glia fate and TUJ1 for neuron fate. The stem cells will differentiate after removing FGF2 and EGF.

Question 36

What are the ways we can differentiate the cell cultures in vitro

Answer 36

One way is to remove the signals that are keeping the cell in an undifferentiated state and provide signals that promote differentiation. But this does not represent real life and it is easiest to see in microscopy. 2D Another way is to let the cells differentiate on their own. They can self organise into embryoid bodies or organoids in the absence of signals. This will represent what happens in the natural environment. But it means we can’t observe the role of individual signals. 3D

Question 37

How can we use stem cells to study microcephaly. Symptoms. What is detected in the cells.

Answer 37

Neurodevelopmental disorder where infants are born with small brains due to a recessive mutation. Causes seizures. Take a biopsy and produce induced pluripotent stem cells from it. Then create cerebral organoids in the dishes. It was found that they had a much smaller number of neurons. DCX shows neuron growth and sox2 shows neural progenitors. There was less of both of these in the microcephaly organoids

Question 38

What is familial dysautonomia How can stem cells be used to study it. And how can it be treated.

Answer 38

Genetic disorder that affects the development and survival of neurons controlling involuntary actions such as digestion and breathing. Have a prominent chin, poor muscle tone, poor growth and lung infections. There is no treatment and they die early. Take a biopsy and make a culture. They showed almost no TUJ1 (neuron Fate) A drug called kinetin can reverse the phenotype and increase the number of neurons in the dish.

Question 39

How to treat Parkinson’s with stem cells

Answer 39

We can create more neurons using stem cells and put them back into the patient There is improvement of motor function.

Question 40

What pathways are important for maintaining stem cells Why is studying stem cells difficult

Answer 40

Notch, BMP, jackstat and wnt. There are very few stem cell markers.

Question 41

What cells are in the crypt of the intestine

Answer 41

Every villus had an associated crypt. The stem cells are just above the bottom of the crypt. The paneth cells are support cells that surround the stem cells. At the very bottom there are the least differentiated cells and as cells differentiate they travel up the crypt and away from the signals causing stem cell fate. They are called transit amplifying cells and they move proximally.

Question 42

Where is wnt expressed in the crypt and what happens because of this Where does wnt come from

Answer 42

Wnt is expressed most at the base of the crypt. This causes lgr5 expression and the cells are known as crypt base columnar cells. The support cells provide wnt signalling and turn on the pathway in the nearby stem cells.

Question 43

What can you make from one cultured stem cell And what can you do with this.

Answer 43

It will grow and form an organoid. If you give wounded animals the organoid it will have an amazing recovery. They can be used as a diagnostic tool for cystic fibrosis for comparisons with the wild type. Therapeutic tool for ulcerative colitis.

Question 44

What is intra and inter tumour heterogeneity

Answer 44

Intra - the differences within a single tumour. Cells within the same tumour often exhibit differences in terms of differentiation and size and proliferation rate. Inter- the differences seen between separate tumours.

Question 45

Stochastic model of tumour cells and is it true

Answer 45

All tumour cells are equipotent for differentiation. The cells that do differentiate are the targets for anti cancer treatment. This model thinks that all tumour cells are equally vulnerable to the treatments, but tumors often recur so not all cells are equally vulnerable.

Question 46

What is the cancer stem cell model and is it right

Answer 46

Only a small subset of tumour cells has the ability for long term self renewal. If you give a drug that kills proliferating cells then some of the differentiating tumour cells will be killed. But the subset of cells that can self renew called cancer stem cells will be resistant to the drug and this is why tumours come back

Question 47

Common features between cancer and normal stem cells

Answer 47

Both able to self renew. Normal ones do it for homeostasis and cancer does it for tumour growth. They can both differentiate. They are regulated by the same signalling pathways. High wnt causes colon cancer and stem cell fate.