linages of early mammalian embryo

Question 1

explain first 3-4 days of development

Answer 1

very dynamic
development is constrained by the cell wall
volume doesnt change when cell progresses from 1 to many
after compaction rough cell look becomes smooth
the cavity is filled with liquid

Question 2

what happens after the blastocyst has formed

Answer 2

it emerges from the zona - the zona creates pressure to stop the cells from sticking ( cell division happen in a tight time frame)

Question 3

what is the cell division pattern important for

Answer 3

the travelling of the embryo from the uterus to the ovary

Question 4

what happens if the egg doesnt hatch

Answer 4

it falls out and no pregnancy occurs

Question 5

when is totipotency lost

Answer 5

after the 5th cell division

Question 6

what is pluripotency

Answer 6

the ability to give rise to somatic cells

Question 7

how can the 4 cell stage be examined

Answer 7

separation of the blastomeres into 4 dishes to give 4 embryos from this stage - theoretically would produce identical quadruplets

Question 8

what are the 3 ways linages can be determined

Answer 8

prepatterning model
inside out model
cell polarity model
LEARN DIAGRAMS FROM NOTES

Question 9

what are the molecular players in the formation of the first lineages in the blastocyst

Answer 9

4 lineage specific transcription factors

Oct4, Cdx2, Nanog and Gata6

Question 10

when is lineage specific expression established

Answer 10

gradually in association with maturation of cellular structures and of positive and negative interaction amongst the transcription factors themselves

Question 11

how and where is Oct4 observed

how is it down regulated and when

Answer 11

in all blastomeres throughout early cleavage stages due to maternally encoded proteins
at the 8 cell stage all blastomeres contain oct 4 but it is gradually down regulated in the outer trophectoderm cells by Cdx2 through physical interaction and transcriptional regulation

Question 12

when is Cdx2 detected
when is it ubiquitous
and where is it restricted

Answer 12

starting from 8-16 cell stage, initial expression is stochastic
by early morula to early blastocysts its expression is ubiquitous and is higher in outer, apically polarised cells
it is restricted in outer TE cells which is established in the blastocyst stage

Question 13

when is Nanog and Gata6 detected

Answer 13

form 8 cell stage both expressed uniformly until early blastocyst stage

Question 14

what is nanog down regulated in outer cells by

Answer 14

Cdx2 in a subpopulation of ICM by Grb-2 dependent signalling

Question 15

what is Gata6 expression maintained by

Answer 15

Grb- 2 dependent signalling

Question 16

when do cells have to express Nanog or Gata6 exclusively by

Answer 16

by the late blastocyst stage

Question 17

in the first differentiation event how do oct4, sox2 and nanog regulate eachother

Answer 17

oct4 sox2 and nanog each regulate each other equally

Question 18

what is cdx2 repressed by in the first differentiation event

Answer 18

oct4 sox2 and nanog and they are repressed by cdx2 - slight imbalance tips production to only one due their mutual inhibitory regulation (small changes accelerate ti become much bigger)

Question 19

how is cdx2 expressed in 8 cell

Answer 19

asymetrically

Question 20

what 2 components break the cycle of the first differentiation event

Answer 20

adhesion to other cells of insides cells and outside cells only having adhesion to one side of their cells

Question 21

what changes the expression of yap protein and what does this regualte

Answer 21

pressure changed expression on YAP - on inside it is cytoplasmic on outside it is nuclear
this regulates the expression of tead4 which regulates cdx2

Question 22

what decides if cells are inside or outside cells

Answer 22

the position of the cell and its expression of cdx2, more cdx2 = movement to the outside (repositioning can occur)

Question 23

what is the importance of the apical membrane

Answer 23

the early embryo is very busy, ezrin is localised when cells divide to give an asymmetric shape/distribution this specifies outside fate
the apical membrane is sufficient to initiate fate segregation

Question 24

what does the second differentiation event rely on

Answer 24

interaction and cross regulation of different transcription factors

Question 25

in the second differentiation event what reduces nanog

Answer 25

MAPK

Question 26

in the second differentiation event how are 2 cell populations divided

Answer 26

by being on either side of the basal membrane

Question 27

what 3 types of cells form the blastocyst

Answer 27

ES cells from the epiblast, XEN cells from the primitive endoderm and TS cells from Trophectoderm

Question 28

how do cells go from ICM to stem cells

Answer 28

pluripotency, can give rise to all embryonic lineages in vitro and vivo, this is used extensively for the generation of KO mice

Question 29

TE to trophoblast stem cell lines

Answer 29

this is self renewing and can differentiate into all TE lineages in vitro and vivo and they have appropriate DNA imprints

Question 30

PrE to extra embryonic ectoderm (XEN) cell lines

Answer 30

gives rise to embryonic endoderm lineages in vitro and vivo
they have peculiar morphology and motility
and have appropriate DNA imprints

Question 31

Blastocyst derived cell lines

Answer 31

only Es derived from humans
TS cells derived from primates
XEN cells to date are only rodent cells
possibly species differences like in ES