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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
- compaction
- human male embryos divide faster than females
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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
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what happens after compaction?
what does each give rise to?
separation of trophoblast from ICM (inner cell mass) - random!
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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
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what's diff about x chromosomes between ICM and trophoblast?
- ICM - pluripotent - still has both x's activated
- trophoblast - only has maternal X activated
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what's the process of making the blastocoel called? which part secretes fluid?
what is the important ion that gets pumped in?
- cavitation
- the trophoblast does
- - Na
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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
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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)
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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)
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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
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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
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what is an ectopic pregnancy?
this is where you get implantation in the oviduct when it should happen in the uterus
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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
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what is the chorion?
fetal part of the placenta
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whats the epi and hypblast called?
bilaminar germ disc
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what key set of cells of gastrulation contribute to making the whole embryo?
embryonic epiblast (same as original epiblast layer)
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what specific movement does the hypoblast do?
delamination to line the blastocoel - making the yolk sac
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fxns of the placenta:
- endocrine
- immunologic
- nutritional
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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
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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
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what does BMP say?
what does Wnt say?
- BMP - be ventral
- Wnt - be posterior
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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
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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
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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
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