unit 3 Flashcards
What is a neural crest?
- transient, multipotent, migratory cells that differentiate into many tissues and organs
- start as 1 thing (neural crest) and go to many types
- epithelial to mesenchymal transition
What surrounds the neural crest?
somites
How does migration occur in the neural crest?
- neural crest to neural plate
- neural plate closes and promigratory cells close in
- delamination of neural crest cells
- then migratory cells
What are the regions of the neural crest?
- cranial
- cardiac
- vagal
- trunk
What is the cranial region of the neural crest?
- forms face, neck, cranial nerves, cartilage, bone, neurons
What is the cardiac region of the neural crest?
- division between aorta and pulmonary artery, cartilage and connective tissue and melanocytes
What is the vagal region of the neural crest?
- parasympathetic ganglia
What is the trunk region of neural crest?
- medulla portion of adrenal gland, sympathetic ganglia, melanocytes, and neurons
How do you study the neural crest?
- use multicolored organisms with CRE
- use mice
How is fate determined in the neural crest?
- start as progenitors and use paracrine signals to determine fate
How is the epidermis formed?
WNT + BMP
How is the placodal cells formed?
Wnt to BMP
How is the neural crest formed?
- Wnt to WNT and BMP
How are neural cells formed?
straight from wnt
What do ecadherins do?
- cell adhesion in stationary cells
What do n cadherins do?
- cell adhesion in migratory cells
What does C6B do?
- stabilizes neural crest
What does SOX2 do?
- keeps neural crest in progenitor stage as delamination progresses allowing for specification
What does snail 2 do?
- TF promoting epithelial to mesenchymal transition
What do lamelpodia and fillipodia do?
- directs growth with RAC1
What do actin and myosin do?
- retract with RHO1
What is contact inhibition?
- if they touch each other they repress and run the other way
What is the contact inhibition pathway?
- touching to cells rearranging to cells looking for vacant openings to populate to proper distribution
What is the premigratory domain?
- high BMP WNT SNAIL2
- repression of E+N cadherin
- SNAIL 1 and C6B upregulated
What do chase and run placodes do?
- form streams and keep cells from mixing
How is collective migration regulated?
- cell to cell adhesion is mediated by low N cadherin
- migratory crest cells secrete attractive signals delineated by chemical cues on the way to target
How does the chase and run placodes work?
- placodes release SEF1 (Chemoattractor) to receptors CXCR4
- placodes attract than the chase begins
- repellants (semaphorins and ephrins keep the cells in line
- contact forms co-inhibition there is a stop of signals so they repel, then they chase again
Where is beta galactosidase expressed?
expressed with WNT and mesoderm derived cells
What do birds and placental organisms have in common?
- amniotic cavity
- embryo
- ammion
- allanlois
- chorion
- yolk sac
- mammary glands
What does an egg have that a placenta doesn’t?
- shell
What does a placenta have that an egg doesn’t
- placenta itself
- umbilical cord
What happens before a chick lays an egg?
- fertilization
- division and growth of living cells
- segregation of cells into layers and tissues
What happens during egg incubation?
- rapid growth
- by day 3 all chicken anatomy is in place
What is the chicken reproductive tract?
- ovary surrounded by infundibulum to capture egg
- to mangum in chicken but fallopian tube in mammals
- narrows to isthmus
- enters into uterus or shell gland where egg undergoes rotation
- layed through cloaca
What is discoidal meroblastic cleavage?
- yolk doesn’t cleave
- all development on top of yolk
What is the zona pellucida?
- zone on top of egg yolk that appears clear
What is the suddermanal cavity?
- between cells and yolk
- like a blastocoel
- allows gastrulation
When does hypoblast formation happen?
- as soon as reductive division and cleavage hypoblasts form and migrate underneath epiblast
- hypoblast cells don’t contribute to embryo, but help gastrulation to take cells from epiblast in
Where does the cell undergo cleavage?
blastodisk
What is the chilazza?
- suspends yolk in shell gland and helps rotate
What is the difference between a blastodisk and blastoderm?
- disk = 1 cell
- derm = many cells
What happens to the maternal determinants in the blsatoderm?
- swept to one side similar to cortical rotation
- cillia goes to molecular sweep leading to biochemical assymetry
- left = cerebrus, nodal BMP
- right = FGF8
What is kohlers sickle?
- helps organizer, gradient of gene products and stabilizes beta catenin
- directs hypoblasts into sudural cells
- form hensons nodes where cells will gastrulate
How does the primitive streak form?
- primary hypoblast to secondary hypoblasts to ingression of epiblasts to subdural mesoderm and endoderm to primitive streak
How does opeca cell formation happen?
epiblast ingression to hypoblast to endoderm to embryonic endoderm
What does the endoderm form?
- respiratory and digestive system
What does the primitive streak do?
- forms anterior posterior axis and undergoes anterior migration
How can you track how cells move?
- use gfps and voltage to force DNA in
- graft cells and implant into recipeint and watch where it goes and how it migrates
Where do cells move if they are anterior to the node?
- move anteriorly
Where do cells move if they are posterior to the node?
- lateral and slightly foward
Where do cells move if they are far posterior?
- only lateral
What is the primative streak equivilant to?
- DBL
What is the convergence of the primative streak?
- ripcurrent causing convergent extension
- uses WNT non-canonical pathway leading to RHO and RAT
What does planar cell polarity cause?
- changes in cytoskeletal dynamics
What happens when henson’s node gets to the posterior?
- it regresses and leaves nodal chord
- moves anteriorly
- noggin is expressed leaving BMP free node
What does FGF to RA to WNT lead to?
FGF blocks RA which blocks wnt
What are the steps to mammalian fertilization?
- capacitation in female reproductive tract uses serum albuteral and calcium, so bicarb goes to camp to PKA to phosphorylation to capacitation
- sense and follow progesterone gradient and thermal gradient
- undergo acrosome reaction qith zona pellucida - proteolytic enzymes breakdwon egg barrier
- fusion of sperm and egg with izumo and juno
- zinc spark activates egg to block acrosomal reaction
Where does early cleavage occur?
- oviduct/ fallopian tube
When does implantation occur?
- when embryo is a blastocyte
What type of cleavage do mammals undero?
- holoblastic isolecithal rotational cleavage
What does cleavage lead to?
- blastocyst
- 8 cells and compaction to morula to blastocyte
What is compaction?
- cell to cell adhesion and loss of individuality using e-cadherins
What does the morula form?
- trophoblast precursors (extra embryonic and lead to placental formation)
- intercell mass ( embryonic cells, extra embryonic cells and membranes
When does the blastocoel form?
16-32 days
How does the blastocoel form?
- highly equal and synchronized division
- embryo cavitates to form blastocoel
- trophoblast cells go inside
- allows Na in and pushes H+ out
- Na+ increases osmatic pressure and blastocoel expansion
Where is OCT4 found?
- in intermast cells
- trophoblast cells don’t have it
- extraembryonic cells don’t have this
What do extraembryonic cells form?
- hypoblast cells that form more extraembryonic structures
What is a pluripotent cell?
- can form many different cells but not all
- requires Oct 4
What type of cell is an epiblast?
- pluripotent
- can self renew
Is a fertilized egg pluripotent?
- no its totipotent
What are the levels of Oct4 expression?
- high = extraembryonic endoderm and mesoderm
- middle = embryonic stem cell
- low = trophectoderm
What do yamenaka cells do?
- can undifferentiate buccal cells into embryonic stem cells
- induce pluripotency
What is the difference between trophoblast and ICM cells?
- trophoblast cells have CDX2
- ICM have oct4
- CDX2 knockouts express Oct 4
- CDX2 cells is trophoblasts requires Tread4