Early Embryo Metabolism

Question 1

In what region of the female reproductive tract does fertilisation occur?

Answer 1

Ampulla region of the fallopian tube

Question 2

At what stage is the embryo first known as a zygote

Answer 2

2 cell stage

Question 3

At what stage does compaction occur?

Answer 3

16-32 cell stage

Question 4

How long does compaction last?

Answer 4

3 to 4 days

Question 5

When does the embryo become a blastocyst?

Answer 5

Following compaction, when the morula is released in to the uterus.

Question 6

What cell changes define blastocyst stage of embryo development?

Answer 6

At blastocyst stage, cells gain developmental competence - stat to form crude cell lineages

Question 7

What is the cell fate of outer cells in blastocyst?

Answer 7

trophectoderm, due to be placenta

Question 8

What is the cell fate of inner cells in blastocyst?

Answer 8

Inner cell mass, due to be fetus

Question 9

Which cellular interaction increases at compaction?

Answer 9

cell to cell adhesion

Question 10

What is the main mediator molecule of increased cell adhesion at compaction?

Answer 10

E-cadherin

Question 11

What dependency do outer cells gain during polarisation at compaction stage?

Answer 11

Calcium dependency

Question 12

In absence of calcium - will compaction occur?

Answer 12

no

Question 13

What secondary protein allows the binding of e-cadherin to actin cytoskeleten in blastomers?

Answer 13

Alpha and beta catenins

Question 14

At what stage of embryo development is e-cadherin expressed?

Answer 14

expressed from early cleavage, but loacalised to regions of cell to cell contact at compaction.

Question 15

What is theory for relocalisation of e-cadherin

Answer 15

Driven by PKc (protein kinase C)

Question 16

What do E-cadherin knockouts, alpha catenin knockouts and embryos treated with e-cadherin antibodies all have in common?

Answer 16

They will fail at compaction stage

Question 17

What is an occludin?

Answer 17

transmembrane protein involved in embryo development

Question 18

What further proteins exist in occludin complexes?

Answer 18

ZO-1, ZO-2 and cingulin

Question 19

At what cell stage does the biogenesis of tight junctional proteins occur?

Answer 19

beginning at 6 - 8 cell stage, up until blastocyst formation

Question 20

Where are TJPs polarised to?

Answer 20

Apical face of cells.

Question 21

What allows embryos to go from permeable to sealed?

Answer 21

formation of tight junctions between cells.

Question 22

What is the blastoceole?

Answer 22

Area of water (and some other factors) found in the middle of the blastocyst

Question 23

Via what mechanism does the blastoceole increase in size?

Answer 23

Due to a sodium gradient, water flows in to the embryo.

Synonymously, tight junctions are being formed, and water is retained in the embryo. Cells become impermeable

Question 24

What are the two main hypotheses for cell polarization in early embryo development?

Answer 24

Inside/Outside hypothesis and Cell Polarity hypothesis

Question 25

What is the main difference between the 2 hypotheses for cell polarisation in early embryo development?

Answer 25

Inside/outside hypothesis assumes that cell division determines the cell fate. Cell Polarity hypothesis assumes that cell fate determines the direction of cell division.

Question 26

Where can Oct4 be found in the blastocyst

Answer 26

Inner cell mass

Question 27

How is Oct4 localised?

Answer 27

Oct4 expression is repressed by Cdx2, found localised to trophectoderm

Question 28

What about the location where Cdx2 is found is special?

Answer 28

At the apical domain of cells where Cdx2 is found, there are exposed cell faces. In all other cells in the blastocyst, there is isometric binding - connected at all faces.

Question 29

Where can Nanog be found in the blastocyst

Answer 29

salt and peppered in Inner cell mass

Question 30

Where can Gata6 be found in the blastocyst?

Answer 30

Salt and peppered in inner cell mass (not in same cells as nanog)

Question 31

How does Grb2 regulate Nanog and Gata6?

Answer 31

Grb2 inhibits Nanog expression and promotes Gata6 expression.

Question 32

In early cleavage embryo, what is the main energy substrate?

Answer 32

pyruvate

Question 33

Up until compaction, what is the main mechanism for energy production in the embryo?

Answer 33

TCA cycle (Krebs cycle)

Question 34

During and after compaction, what is the main mechanism for energy production in the embryo?

Answer 34

glycolysis

Question 35

At what point of embryo development would you expect to see lactate production increase?

Answer 35

compaction

Question 36

what mechanism do cumulus cells utilise to provide energy substrate for the oocyte?

Answer 36

glycolysis (to produce pyruvate)

Question 37

What is the main product of the PPP pathway in cumulus cells?

Answer 37

NADPH

Question 38

What is the main effect of the accumulation of ATP in early embryo? (other than use for energy)

Answer 38

Disrupts the ATP:ADP ratio having a negative impact on the production of phosphofructokinase (PFK), so glycolysis cannot occur.

Question 39

How is the ATP:ADP ratio restored?

Answer 39

use of ATP for high energy processes eg compaction

Question 40

Other than glycolysis, what is glucose used for in the embryo?

Answer 40

basic material required for nucleic acid synthesis, required for phospholipid and non essential amino acid biosynthesis.

Question 41

What are glucose transporter proteins known as?

Answer 41

GLUT

Question 42

When is GLUT4 expressed?

Answer 42

Only expressed from blastocyst stage onwards

Question 43

When is GLUT5 expressed?

Answer 43

GLUT5 expression begins at 8 cell stage

Question 44

Are embryos that have high glucose uptake more or less likely to be viable?

Answer 44

More likely

Question 45

Are embryos that have high rates of glycolysis more or less likely to be viable?

Answer 45

Less

Question 46

what effect does culturing embryos in high oxygen concentration have?

Answer 46

toxic

Question 47

High production of alanine at early embryo stages can be an indicator of what?

Answer 47

embryo arrest

Question 48

What will happen to embryos which have high metabolic activity and use of amino acids at very early stages?

Answer 48

they will fail :( (metabolic stress)