Germ Layer Specification Flashcards
(20 cards)
What are the three germ layers?
Ectoderm, Mesoderm, Endoderm
What does the ectoderm form?
Epidermis, CNS, neural crest derivatives
What does the mesoderm form?
Muscle, bone, kidneys, reproductive system
What does the endoderm form?
Gut lining, lungs, liver, pancreas
Where do germ layers originate from?
Epiblast cells that migrate through the primitive streak
What signals induce ectoderm?
Low BMP activity (inhibited by Noggin, Chordin, Follistatin)
What signals promote epidermal fate?
High BMP activity
What transcription factors maintain pluripotency before specification?
Oct4, Sox2, Nanog
What is the key signal for mesoderm induction?
Nodal + FGF + Wnt
What determines mesoderm subtypes?
Nodal concentration gradient
What specifies endoderm fate?
High Nodal + FoxA2 + Sox17
What region secretes Nodal antagonists anteriorly?
Anterior visceral endoderm (AVE)
Which mesoderm type becomes the notochord?
Axial mesoderm
Which mesoderm becomes somites?
Paraxial mesoderm
Which mesoderm becomes kidneys and gonads?
Intermediate mesoderm
Which mesoderm becomes limb and body wall?
Lateral plate mesoderm
What establishes initial A-P polarity?
Nodal and Wnt signalling gradients
What is the role of FGF in mesoderm formation?
Promotes mesoderm induction and streak elongation
How is the ectoderm “protected” from mesodermal fate?
Lack of Nodal signalling and presence of BMP inhibitors
What experimental tool is used to trace germ layer fate?
Lineage tracing or fate mapping
