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Development > Mice > Flashcards

Mice Flashcards

1
Q

In placental mammals there is an extra stage to development. What is it?

A

Implantation of the embryo to the uterus wall.

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2
Q

Why are mammals difficult to study?

A

Development is internal, thus pre-implantation development is more widely studied.

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3
Q

When does implantation occur?

A

Between blastulation and gastrulation.

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4
Q

Why do scientists record the time as E0.5 at the start of development?

A

Mice mate during the night, thus 0.5 refers to the half day that has already passed when they are checked on in the morning.

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5
Q

In mammals where is the egg fertilised?

A

Near the ovary in the oviduct.

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6
Q

What is the zone pellucida?

A

A membrane that prevents ectopic pregnancy.

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7
Q

Define the process of compaction.

A

When the blastula compacts to form the morula.

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8
Q

Define the morula.

A

A solid ball of cells.

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9
Q

What happens when the morula is formed?

A

The cells become polarised. Microvilli interdigitate and pull the cells together.

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10
Q

The morula is still permeable to external fluid. True or false?

A

False - the morula is impermeable to external fluid.

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11
Q

What happens during the process of cavitation?

A

Phenotypic differences appear in the inner and outer cells.

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12
Q

During cavitation, describe the a) outer and b) inner cells.

A

a) larger and polarised

b) smaller and apolar

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13
Q

What forms the blastocoel within the morula?

A

Transportation of vectorial fluid from the outside to the inside of the morula.

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14
Q

What do the outer cells of the morula become?

A

Trophoectoderm (TE).

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15
Q

What is the trophoectoderm fated to become?

A

Chorion, which in mammals contributes to the formation of the placenta.

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16
Q

What do the inner cells become?

A

The inner cell mass (ICM)

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17
Q

What is the ICM fated to become?

A

Amnion and embryo proper.

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18
Q

What are the chorion and amnion important for?

A

Gas exchange.

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19
Q

What 3 types of cell are born from the TE?

A
  1. Trophoblast stem cells
  2. Giant trophoblast cells
  3. Placental cells
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20
Q

The ICM is subdivided into what 2 things?

A
  1. The outer ICM becomes the primitive endoderm (PrE)

2. The inner ICM becomes epiblasts (EBs)

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21
Q

What does the PrE become?

A

Amnion

22
Q

What do the epiblasts give rise to?

A

The embryo proper.

23
Q

What 2 genes are expressed by the TE?

A

Eomesodermin and Cdx2

24
Q

What gene do all ICM cells express?

A

Oct4

25
Q

What is the function of Oct4?

A

It down-regulates Eomes and Cdx2, preventing ICM from becoming TE.

26
Q

What is the interaction of Oct4 and Eomes/Cdx2 described as?

A

Mutually repressive.

27
Q

What 3 genes are only expressed by PrE?

A
  1. GATA6
  2. GNCF
  3. Sox17
28
Q

What 3 genes are only expressed by epiblasts?

A
  1. nanog
  2. Sox2
  3. Stat3
29
Q

Epiblasts can give rise to any cell in the embryo. True or false?

A

False - they can give rise to any cell from the embryo proper but cannot form embryonic membranes.

30
Q

There are 2 theories for the formation of TE and ICM. What are they?

A
  1. Polarisation theory

2. Inside-out model

31
Q

There are 2 theories for the formation of TE and ICM. Explain the polarisation theory.

A

The polarisation that occurs during compaction alters the distribution of cytoplasmic determinants. The polarised outer cells become TE and the apolar inner cells become ICM.

32
Q

There are 2 theories for the formation of TE and ICM. Suggest support for the polarisation theory.

A

Division is asymmetrical.

33
Q

There are 2 theories for the formation of TE and ICM. Explain the inside-out model.

A

Compaction creates different microenvironments for the outer and inner cells, e.g. exposure to fluid (outer) or not (inner).

34
Q

What do TEAD4 mutants lack?

A

TEAD4 mutants lack Cdx2 activation and thus do not develop TE.

35
Q

What does TEAD4 require in order to activate Cdx2?

A

A co-factor called YAP

36
Q

How is Cdx2 activated?

A

By the translocation of TEAD4 and YAP to the nucleus.

37
Q

YAP and lats are involved in the Hippo signalling pathway. What is Hippo signalling for?

A

Tumour suppression.

38
Q

Briefly explain Hippo signalling.

A
  1. Hippo is a transmembrane protein that activates lats
  2. lats phosphorylates YAP
  3. YAP degrades
  4. TEAD4 cannot activate Cdx2 if YAP is degraded
39
Q

It is thought Hippo signalling occurs in the ICM. Why?

A

The physical contact of cells in the ICM creates enough critical mass to activate Hippo. This then inactivates Cdx2.

40
Q

Hippo signalling does not occur in the TE. Why?

A

The TE is on the outside and has reduced contact with other cells.

41
Q

There are 3 theories for the formation of PrE and EB from the ICM. What are they?

A
  1. The positional model
  2. Stochastic model
  3. Time-outside/time-inside model
42
Q

There are 2 theories for the formation of PrE and EB from the ICM. Explain the positional model.

A

The different microenvironments in cavitation create different cell fates.

43
Q

There are 2 theories for the formation of PrE and EB from the ICM. What is a flaw in the positional model?

A

Early on in development all cells there is a homogenous distribution of cells and thus no variation in microenvironment.

44
Q

There are 2 theories for the formation of PrE and EB from the ICM. Explain the stochastic model.

A

The expression of PrE or EB markers overlap in the morula, which causes cellular migration.

45
Q

There are 2 theories for the formation of PrE and EB from the ICM. Explain the time-outside/time-inside model.

A

Developmental origin causes differentiation: the first cells to internalise are the EB and these express nanog. The last cells to internalise are the PrE and express GATA6.

46
Q

All the cells in a mouse embryo are totipotent up the 8-cell stage. True or false?

A

True.

47
Q

The totipotency of cells up to the 8-cell stage is responsible for identical sibs. True or false?

A

True.

48
Q

What does the fusion of two 8-cell mammalian embryos result in?

A

A normal chimera.

49
Q

Fusing 8-cell embryos from other species also forms chimeras. True or false?

A

False - only the fusion of 8-cell mammal embryos foms chimeras.

50
Q

What does GRN stand for?

A

Gene regulatory network.

Development (18 decks)

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