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Developmental And Stem Cell Biolody > Pre-implantation development > Flashcards

Pre-implantation development Flashcards

1
Q

State the stages between zygote and expanded blastocyst

A

zygote
2-cell
4-cell
8-cell
late morula
early blastocyst
expanded blastocyst

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2
Q

What surrounds the embryo at the 4-cell stage

A

the zona pellucida

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3
Q

At what stage does compaction occur

A

8-cell stage

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4
Q

When does zygotic genome activation occur both in mice and mammals?

A

mice = the 2-cell stage
mammals = the 2-4 cell stage

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5
Q

What is the success of artificial twinning dependent on

A

the number of cells that end up in the epiblast

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6
Q

What events occur during the 8-cell stage?

A

cells become polar and have an inside and outside. cells with a free surface (unattached to another cell) accumulate actin
cells become compacted

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7
Q

What stage does cavitation occur and what happens

A

the 16-cell stage
tight junctions seal off the membrane and make gaps so cells are impermeable to water and salts
the blastocyst cavity forms

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8
Q

How does the blastocyst form?

A

Na and Cl move into the blastocyst and water moves in. increase in osmotic pressure and blastocyst expands. a major energy-requiring process as Na is pumped

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9
Q

What substance can artificially induce compaction

A

PKC

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10
Q

What is aneuploidy

A

an abnormal number of chromosomes, normally leads to embryo arrest when implanted to the mother in IVF

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11
Q

What factors make an embryo in IVF more likely to be chosen for implantation

A

expanded blastocyst, more rapid cell divisions, even cleavage divisions

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12
Q

What is pre-implantation genetic testing for aneuploidy (PGT-A)?

A

at the 8-cell stage, one cell is removed and analysed using next generation sequencing to test for aneuploidy. as all 8 cells are identical, diagnosing one cell will diagnose all

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13
Q

What is embryo mosaicism?

A

cells in different regions of the embryo having different levels of aneuploidy - leads to risk of misdiagnosis

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14
Q

Why is there an increase in oxygen consumption at the blastocyst stage?

A

due to presence of Na pump and action of glycolysis and mitochondria

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15
Q

What environment should embryos be grown on a culture medium for optimum growth?

A

2 steps:
1 = treat with pyruvate
2 = treat with glucose
culture should have a low oxygen of 5%

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16
Q

What is the zona pelucida made up of? What does it do?

A

Glycoproteins of matrix of cell. Protects egg from poly-sperm

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17
Q

What occurs during the cleavage stage?

A

Increased embryo gene expression

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18
Q

What occurs during compaction?

A

Loss of blastomere definition- through increase cell adhesion and tight junction formation

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19
Q

WHAT OCCURS DURING CAVITATION?

A

Inner cell mass formation
Trophectoderm Na/ K -ATPase pump creates classical cavity- pump fluid- to generate fluid filled balls

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20
Q

What is the inner cell mass?

A

A mass of cells within the blastocysts in the early development of an embryo which neutrally gives rise to structures of the fetus

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21
Q

What does the Trophectoderm do?

A

Creates supporting tissues

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22
Q

What occurs during implantation?

A

Initiated by adhesion between Trophectoderm and uterine endometrium

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23
Q

What causes delayed implantation?

A

Through hormonal control- oestrogen determines blastocyst and uterine endometrium interaction- unfavourable conditions for pregnancy

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24
Q

What is the mechanisms of Trophectoderm and inner cell mass allocation?

A
  1. Establish polarity within cell - allows different communication lines
  2. This enables cell to organise polarity within the embryo and establish paths for intercellular communication
  3. Cell differentiation and allocation to different lineages involes estabilishing spatially restricted patters of gene expression
  4. Critical fate determining gene of important include:
    Cdx2 a TF that signals for trophoblast
    GATA4/6- primitive endoderm
    Oct4/ nanos- inner cell mass
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25
Q

What genes give rise to the subcortical maternal complex?

A

Za1, mater, floped and padi6

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26
Q

What do outside cells activate and repress?

A

Activate Cdx2
Repress oct4/ Nanog

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27
Q

What do inside cells repress and activate?

A

Cdx2 repressed
Oct4/ Nanog activated

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28
Q

What specifies the Trophectoderm?

A

Cdx2

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29
Q

What specifies the inner cell mass?

A

Oct4 and Nanog

30
Q

How is Cdx2 gene activated in outside cells repress?

A

Hippo activation of last that in turn regulates Yap- is controlled by the extent of cell-cell contact.
Lower cell-cell contact- causes Yap to bind to Tead4- turning Cdx2 on

31
Q

What does high cell-cell contact lead to for Yap?

A

Phosphorylation of Yap= negatively regulates YAP - so cdx2 off

32
Q

What happens in Nanog and oct4 mutant embryos?

A

Defective in ICM formation

33
Q

What does the primitive endoderm differentiate to?

A

Extraembyonic endoderm- to make yolk sac and amnion

34
Q

What is pluripotency?

A

Non-restricted potential to commit to all germ layers and differentiate to all cell types of body.

35
Q

What did sir martin Evan’s do?

A

Isolated ICM - demonstrated self renewal

36
Q

Name the stages from spermatogonia to spermatozoa?

A

Spermatogonia> primary spermatocytes> secondary spermatocytes> spermatids > spermatozoa

37
Q

Name steps from oogonia to oocyte?

A

Oogonia> primary oocyte > oocyte

38
Q

Where does the sperm mature in the testes?

A

Near the tail of the epididymis

39
Q

Where is spermatozoa formed?

A

In seminiferous tubules

40
Q

What is the role of follicular cells?

A

Support the oocyte

41
Q

What is the difference between metaphase I and metaphase II in Oogenesis?

A

Metaphase I has one meiotic spindle whereas metaphase II has a secondary meiotic spindles

42
Q

Where does fertilisation take place?

A

In the uterine tube

43
Q

When does oocyte proliferation stop?

A

Before birth

44
Q

When does the first meiotic division begin?

A

During puberty

45
Q

When does the first polar body get emitted?

A

Before ovulation

46
Q

When is the peak number of germ cells in humans?

A

4-6 months

47
Q

When do the two polar bodies and two pro nuclei form?

A

After fertilisation

48
Q

At what point does the fertillisation of a clam occur?

A

GV oocyte

49
Q

At what point does the fertillisation of insects ascidians occur?

A

MI oocyte

50
Q

What point do vertebrates become fertilised?

A

MII oocyte

51
Q

At what point does the fertillisation of a a sea urchin and jellyfish occur?

A

Egg

52
Q

At what point do gap junctions disappear?

A

When fertilised

53
Q

What is the role of cortical granule exocytosis?

A

Form a thick barrier, called a fertilisation envelope, stops polyspermy

54
Q

What does a positive Action potential do to fertilisation?

A

Blocks it

55
Q

What does the acrosome reaction do?

A

Leads to Ca2+ influx

56
Q

What does cortical granules do?

A

They undergo exocytosis, release Ovastacin and Zn2+, leading to proteolysis so zona hardening

57
Q

How does mouse fertilisation occur?

A

Izumi bind juno receptor, leading to juno shedding

58
Q

What is physiological polyspermy in newts, birds and reptiles?

A

Female pro nucleus, selects one male pro nucleus and others die. No cortical granules, no membrane depolarisation

59
Q

During egg activation what events can calcium release trigger?

A

Completion o meiosis
Cortical granule exocytosis
Metabolic stimulation (e.g pH rise in sea urchins)
Changes in protein synthesis
Onset of mitotic cell cycles
Membrane potential changes

60
Q

What causes a cortical flash? What does it prevent?

A

Due to action potentials. Prevents more than one sperm entering

61
Q

What are protosomes?

A

The site of gastrulation is said to give rise to the mouth.

62
Q

What are deuterostomes?

A

Forms the anus with the mouth arising from a second opening distant to the site of gastrulation is

63
Q

What causes egg activation in drosophila?

A

Ovulation- in which ca2+ waves without a sperm, driven by a ca2+ influx

64
Q

How does polyspermic fertilisation in newt eggs occur?

A

Many sperm fuse and release calcium but only has a limited calcium wave- so egg is activated by the summation of calcium waves- in which usually 10-20 sperm are needed

65
Q

What is the mechanism of egg activation?

A

Ca2+ triggers CaMKII which phosphorylates EMI2 to APC which activate cycling/CDK1

66
Q

What happens when EMI2 is blocked?

A

When destroyed it allows APC to break down cyclone/cdk1

67
Q

What are the two proposed mechanisms of how calcium release is triggered?

A

Receptor mechanism or soluble sperm factor

68
Q

What is the receptor mechanism?

A

A receptor in the egg is activated by the sperm bind which triggers a signaling pathway involving InsP3, leading to calcium release

69
Q

What is the soluble sperm factor?

A

A Soluble actor from inside the sperm fuses with the membran- setting up a signalling pathway- releasing calcium but only

70
Q

What is Phospholipase C (zeta)?

A

70kDa protein
That is sperm specific found in all mammals-

Associated with soluble sperm factor theory- So triggere InsP3 and so calcium relased

71
Q

Where is PLC (zeta) localised?

A

The equatorial region of the sperm head

72
Q

What happens if PLC zeta is knocked out in mice?

A

No oscillations occurs

Developmental And Stem Cell Biolody (9 decks)

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