Flashcards in Week 6 Cell Differentiation & Stem Cells- Holy Deck (18):
cell fate is already assigned during cleavage, strict developmental plan in place
*removal of one of more cells will result in a INCOMPLETE EMBRYO
-not in mammals, only happens in "lower level" animals
blastomere initally has similar developmental potencies, each capable of giving rise to a complete embryo. Differentiation responsive to enviornmental siganls
*removal of cells will still give you COMPLETE individual, fate not determine early on
cells fail to adhere together normally and fall apart into two masses, each mass is able to give rise to an entire individual if it occurs early enough
Totipotent- can give rise to all embryonic, and extra embryonic cell types and structures
Pluripotent- can give rise to all embryonic cell types and structures
Multipotent- can give rise to multiple (but not al cell types)
Unipotent- can give rise to just one type of cell
ability of one cell to influence the development of another cell. How cell fate is specified during cell differentiation in humans
What is a morphogen?
signal that alters cell fate
Types of Signaling
Paracrine- involves diffusible molecules
Juxtacrine- involves cell-cell contact
Autocrine- cells stimulate themselves
Gradients- important in embryonic developmen, responds to gradients of morphogens, depends on "amount" of morphogen
How is trophoblast (outer) and inner cell mass fates decided?
Hippo signaling pathway
Cdx2 becomes expressed ONLY in trophoblast cells via hippo signaling
Hippo pathway remains active in inner cells (expresses Oct4, Nanog and Gata)
Epiblast and hypoblast formation is decided by
differential expression of transcription factors!
Oct4/Nanog OR Gata (but not both)
Nanog/Oct4 = epiblast
How is Dorsal-ventral determined?
Neural tube differentiation
Notochord induced ventral floor of neural tube to secrete SONICE HEDGEHOG
Overlaying ectoderm induces dorsal roof plate to secret BMP
How is left-right axis determine?
Ciliary cells of primitive node establish directional fluid flow from left to right
leftward flow increases expression of Nodal on left side (some nodal still expressed on right), nodal stimulates production of Lefty
Lefty inhibits Nodal on Left side but not on right
nodal on right stimulates Pitx2
How is anterior-posterior axis determined?
Hox (homeobox genes)- DNA binding protein that acts as a transcription factor
organized on gene complex in same general order as ant-post axis
Retinoic Acid regulates Hox expression
Differentiating of specialized cells types and tissues in the body is due to...
instructed by a HANDFUL of signaling pathways. The big 5
What are cadherins?
mediate selective cell-cell adhesion in tissues specific patterns. Cadherins only bind to similar types --> differential cell adhesion
What induces cell migration and adhesion?
Handful of signaling pathways activate transcription factors such as SNAIL which regulates genes involved in motility and adhesion
Two essential features of stem cells
-Stem cells are not terminally differentiated, but can give rise to daughter cells that can terminally differentiate
-Stem cells can self-renew by dividing and producing two daughter cells, at least one of which does not enter the differentiation pathway but remains a stem cell.
When do we carrying out epigenetic reprogramming?
-shortly after fertilization (preimplantation reprogamming)- demethylation is incomplete
-During primordial germ cell determination, demethylation is complete to allow earsing of imprinted regions according to the sex of the embryo