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how is mammal dev different?
- very slow b/c internal so you can take your time
- asynchronous (not all cells divide at the same time so you can have an odd number of cells at points in time)
- genome activated early (2-8 cells) so no mid blastula phase
- rotational holoblastic cleavage
- human male embryos divide faster than females
what is compaction?
- 8 cell stage/nonpolar: cells are loosely associated
- compact 8 cell stage: polar, e cadherin causes them to tightly compact, tight junctions to seal off the embryo
what happens after compaction?
what does each give rise to?
separation of trophoblast from ICM (inner cell mass) - random!
describe the 16 cell stage and the 32 cell stage:
16 - morula - cells inside have gap junctions, cells outside have tight junctions
32 - blastocyst - formation of trophoblast (outside) that gives rise to the chorion. then the ICM gives rise to embryo, yolk sac, allantois, and amnion - pluripotent, also creation of blastocoel (NaKATPase helps create osmotic gradient - fluid transport
what's diff about x chromosomes between ICM and trophoblast?
- ICM - pluripotent - still has both x's activated
- trophoblast - only has maternal X activated
what's the process of making the blastocoel called? which part secretes fluid?
what is the important ion that gets pumped in?
- the trophoblast does
- - Na
how do the trophoblast cells differ from the ICM cells gene expression wise?
how does this happen?
- trophoblast: have cdx2 and eomes
- ICM: have Oct 4, nanog, and Stat3
story: initially each blastomere expresses cdx and oct 4, tropho continues to express cdx2, but lots of cdx blocks Oct 4 and nanog
what is story of nanog?
- keltic land that establishes eternal youth (goes along with pluripotency)
- prevents ICM from becoming hypoblast (ICM = epiblast embryonic stem cells)
how do they make induced pluripotent stem cells?
take adult stem cells and get them to turn on same genes as IMC (oct 4, nanog, stat3)
what causes the icm do differ from the trophoblast cells?
something about being inside and completely surrounded causes a transcription factor to never get to the nucleus to turn on Cdx2
describe what happens to a human embryo from fertilization to implantation:
- it divides as its moving through the oviduct
- day 6 it loses its ZP before it enters the uterus
what is an ectopic pregnancy?
this is where you get implantation in the oviduct when it should happen in the uterus
how does the blastocyst hatch from the ZP once it gets in the uterus?
- digests a small hole in the ZP which it hatches out of
- endometrium (lining of uterus) has sugars, collagen, laminin, fibronectin, cadherins, HA, heparin sulfate receptors which the trophoblast cells connect due via L - selectin
then secreted Wnt causes the blastocyst to BURY itself in the uterus
what is the chorion?
fetal part of the placenta
whats the epi and hypblast called?
bilaminar germ disc
what key set of cells of gastrulation contribute to making the whole embryo?
embryonic epiblast (same as original epiblast layer)
what specific movement does the hypoblast do?
delamination to line the blastocoel - making the yolk sac
fxns of the placenta:
what are important molecules that coat the epiblast cells before they migrate through primitive groove?
- HA - attaches to water and helps them move and remain individual cells
- fibronectin- lateral migration
what are the 2 signalling centers in the mouse ?
The node: info for whole body - chordin, noggin
AVE (anterior visceral endoderm): info for head formations - cerberus, otx2
what does BMP say?
what does Wnt say?
- BMP - be ventral
- Wnt - be posterior
what is Kartagener’s syndrome ? and whats important about it?
- - organs are not on correct side of the body
- also have problems with cilia so they thought maybe L/R axis has something to do with cilia
mouse mutant phenotypes related to L/R symmetry:
- - randomization (of individual organs) mutation in iv gene - ciliary dinein
- - complete inversion (mutation of inv gene)
monocilia pushing fluid LEFT
what gets pushed left?
FGF releases the NVPs (nodal vesicular parcels) - rise in Ca on left side of node - different gradients of activin and Shh