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Regulation Of Gene Expression > Lesson 17 > Flashcards

Lesson 17 Flashcards

1
Q

if the sperm and egg fuse properly, they will form a single cel which is surrounded by what?

A

membrane pellucida

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2
Q

what is the function of the membrane pellucida?

A

protects the embryo from the maternal tissue

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3
Q

how long does the journey from the oviduct to the uterus take in humans?

A

5 days

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4
Q

when traveling from the oviduct to the uterus, the single cell starts dividing into what?

A

blastomeres

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5
Q

what do the blastomeres form?

A

the morula phase →each of the cells in this phase are able to give rise to an entire individual

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6
Q

as cells in the morula phase grow, what do they form?

A

a cavity forms and the embryo becomes a blastocyst

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7
Q

describe the blastocyst:

A

first developmental stage in which, within the embryo, there is a separation of the developmental potential of the cell

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8
Q

what are the flat cells that generate the walls the blastocyst?

A

trophoblast cells

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9
Q

what do trophoblast cells do?

A

protect a mass of about 50 internal cells called the inner cell mass (ICM)

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10
Q

what are the function of the cells in the ICM?

A

cells that give rise to the entire individual

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11
Q

what do trophoblast cells form?

A

give rise to the embryonic part of the placenta

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12
Q

what is another term for ICM cells?

A

pluripotent stem cells → they can give rise to everything, except the extra-embryonic (placental) tissue

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13
Q

what are cells from the ICM of the blastocyst called in vitro?

A

embryonic stem cells

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14
Q

the culture medium used to grow cells is composed of ions and and glucose necessary for growth, animal serum, and a molecule called Leukemia Inhibitor Factor (LIF), what is the function of the serum?

A

important in maintaining pluripotency

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15
Q

once the embryo develop to form a fetus, what can be harvested?

A

only adult stem cells - organ specific

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16
Q

how long are totipotent cells in the zygote?

A

between days 1-5

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17
Q

how long are pluripotent cells available?

A

between 5-10 days

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18
Q

what are adult stem cells considered as?

A

multopotent: they can differentiate into some cell types but very few

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19
Q

what is present in the embryo to generate the brain?

A

the neural tube

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20
Q

what does the neural tube form?

A

develops in the fetus to generate the anterior part of the brain and the spinal cord in the posterior

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21
Q

what is the neural tube generated from?

A

the neural plate

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22
Q

what is the neural plate generated from?

A

specified from the ectoderm which gives rise to neural progenitors

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23
Q

what two different tissues is the ectoderm split into during development?

A

neural plate and epidermal tissue

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24
Q

what will the neural plate produced from the ectoderm form?

A

all brain, spinal cord, and neural projections

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25
Q

what will the epidermal tissue formed from the ectoderm form?

A

the epidermis and the epidermal sheets

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26
Q

what are BMP factors?

A

bone morphogenic proteins: get expressed from the epidermis and specify the epidermal tissue

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27
Q

how are neural progenitors protected from the signal of BMPs?

A

fibroblasts growth factors (FGF-2)

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28
Q

what is the function of FGF-2?

A

block the action of BMPs and specify the ectodermal cells to become neural progenitors

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29
Q

what is a way to define the pluripotency of ESCs?

A

re-innoculoate them into animal cells (in-vivo)

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30
Q

how are ESCs re-innoculated?

A

they are taken from the dish and re-injected into a host blastocyst → inject about 20 ESCs into a single blastocyst and implant this into a mouse

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31
Q

if this implanted blastocyst implants, what does it create?

A

continue in embryonic development and generate an embryo and then a fetus → chimeric animal

32
Q

chimeric animals are generated by two different cell types - what are they?

A

one cell type is the inner cell mass of the host blastocyst and the other are the ESCs cultured in vitro that we injected into the blastocyst

33
Q

how can they tell which cell type was generated in the mice?

A

host blastocysts from come from mice with a white coat, while ESCs are generated from colored-coated animals

34
Q

what occurs if you inject these cells as they are in vitro, to an adult animal?

A

they will generate a tumor of embryonic origin

35
Q

what is the name of the tumor produced if these stem cells are injected into an adult mouse?

A

teratoma → they form large tumoral masses without metastasis and inside the tumors there are islands of differentiated cells of any kind

36
Q

name the two chemical inhibitors found to be necessary to give the cells the ability to maintain their pluripotency?

A

PD0325901 and CHIR99021

37
Q

what is the PD0325901?

A

small inhibitor of the FGF pathway

38
Q

what is CHIR99021?

A

inhibits the GSK3 pathways which is part of the Wnt pathways

39
Q

what other chemical inhibitor works in the same pathway along with PD inhibiting FGF4?

A

SU5402

40
Q

what do FGFs cause?

A

cause the iPS cells to start to differentiate

41
Q

pluripotency is not something that can be acquired - how must it be present?

A

something that occurs in the basal condition

42
Q

Wnt molecules bind to the receptors on the membrane of a cell that are what?

A

frizzled

43
Q

what do frizzled cells cause?

A

block the pathway → release functional β-catenin

44
Q

what is the function of β-catenin?

A

a transcription
factor which is in the cytoplasm in its inhibited state, but when activated it’s internalized in the nucleus and it
works by activating a number of genes, which are the genes that are for factors of pluripotency

45
Q

what is able to activate the same pluripotency in the same genes as β-catenin?

A

STAT1/3 → both activate the network of transcription facts that stimulate the pluripotency

46
Q

what are the three pluriptency factors stimulated by β-catenin and STAT1/3?

A

Oct4, Sox2, Nanog

47
Q

what is Oct4?

A

is the POU containing transcription factor → POU is the domain of the transcription factors which enables this protein to binding DNA to a specific target and activate or repress it

48
Q

what is Sox2?

A

a transcription factor of a different class and binds the DNA to a different domain which is called HMG-box

49
Q

what is Nanog?

A

a nuclear factor which has another domain, that binds the DNA to regulate its starter genes, which is a homeodomain

50
Q

where is Oct4 specifically expressed?

A

in the cells of the inner mass because it is expressed to maintain pluripotency → if Oct4 is inactivated these cells cannot proliferate

51
Q

what do these three transcription factors codify for?

A

three transcription factors which go into the nucleus and activate the promotor of their own genes

52
Q

three transcription factors which go into the nucleus and activate the promotor of their own genes → what does this activate?

A

feed-forward loop because
their proteins bind to the promoter
of their genes and stimulate the
expression of their transcript and
therefore the production of more
proteins

53
Q

why is the feed-forward loop essential?

A

when activated it maintains in a stable way the expression of this protein

54
Q

what does the culture of human embryonic stem cells require that is different than mice?

A

ESCs do not contain LIF serum, but require FGF2 and active without serum to complete a different signal

55
Q

describe the appearance of human ESCs in culture:

A

they are very flat

56
Q

how must we culture human ESCs?

A

we have to expand them not to make
single cell culture but to make small aggregates because they don’t have the capacity as single cells to grow

57
Q

what is the epiblasts stage?

A

a state where the inner mass already starts to generate an ectoderm

58
Q

why are they called epiblast stem cells?

A

they are not generated from the inner cell mass but they are later derivatives from the inner cell mass, in particular the epiblast

59
Q

why are epiblast stem cells pluripotent?

A

in vitro they can still give rise to everything but in vivo, they don’t because injected into the inner cell mass they don’t give rise to chimeras

60
Q

epiblast stem cells are very similar to the human ESC, and what does this indicate?

A

the human embryonic stem cells are not generated from the inner cell mass but from an embryo that is a little bit older than the blastocyst and are derived from later derivatives of inner cells mass

61
Q

in order to distinguish between embryonic stem cells and epiblast stem cells, what are the two different phases called?

A

the first are called primary or naive pluripotent stem cells and the second are called primed pluripotent embryonic stem cells

62
Q

what is the concept of developmental timing?

A

the process by which the progenitor cells start to its differentiate process becoming mature, differentiated cells → in this process each cell initially is pluripotent and has a very large developmental potential

63
Q

how did scientists clone fibroblasts into retroviruses?

A

they isolated these fibroblasts from a transgenic mouse which carried a
reporter which is called βgeo
which is inserted into the
FBX-15 gene locus

64
Q

what did scientists discover when they cloned fibroblasts into retroviruses?

A

they found that very few cells infected with these combinations of factors changed the morphology
dramatically: they became very small, and they started to grow as island, very similar to the islands of the mouse embryonic stem cells

65
Q

what did they find were necessary to start the conversion form adult fibroblasts into embryonic stem cells?

A

only four factors → iPS cells (induced pluripotent stem cells)

66
Q

what are iPCs?

A

they reacquired the pluripotency: the ability to differentiate their cell type, to grow like mouse embryonic stem cells, but are induced from adult cells trough the forced expression of 4 factors

67
Q

what four factors induce iPCs?

A

Oct4, Sox2, Klf4, and c-Myc → all genes that code for transcription factors

68
Q

what are is the function of the four transcription factor that induce iPCs?

A

goes in the nucleus and bind to hundreds of targets and activate all the transcriptional pathways which are
necessary for pluripotent stem cells, and at the same time repress the genes which are active in the
differentiated cells

69
Q

what did they use to prove IPS-cells were generated by the fully mature hepatocyte and not from progenitors in the cultures?

A

albumin → a factor expressed only in mature hepatocytes = Cre recombinases will only be expressed in mature hepatocytes

70
Q

what happens when they cross a transgenic animal with an animal that has a constitutive promotor CAG (stop reporter)?

A

a constitutive promotor is expressed in any cell type - both embryo and adult

71
Q

what was an important discovery made when studying if fully mature hepatocytes can be reprogrammed into iPCS cells?

A

fibroblasts are mature cells, but they don’t fulfill a very important metabolic process. While mature hepatocytes are fully well differentiated specialized
cells and yet these 4 transcription factors are sufficient to completely revert the identity from a metabolic cell
to an embryonic IPS-cell

72
Q

what is the idea of cell reprogramming?

A

the idea that we can reprogram the identity of cells altogether

73
Q

what is another name for Oct4, Sox2, Klf4, and c-Myc?

A

Yamanaka factors

74
Q

what did they discover about derived IPS cells?

A

in the early stages of differentiation there still is a memory of the cells which they derived from

75
Q

what must occur in order to completely cancel epigenetic memory of the cell of origin?

A

the IPS-cells need to be
stabilized in their reprogramming state in order to lose completely the epigenetic memory of the cell of origin

76
Q

what does epigenetic memory mean?

A

the lasting genes of the cell of origin are still active in the IPS cell

Regulation Of Gene Expression (28 decks)

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