lecture 17 Flashcards
Explain the overview process of development
Positional information (cell signalling) ->
Differentiation (differential gene expression) or Morphogenesis (Growth/change in cell shape) ->
Development (Zygote -> organism)
What is development?
Cell biology in action
e.g.
Cell proliferation and death
Cell signalling
Changes in cell shape
Common model organism for testing development
Nematodes - Transparency, screened for drug effects
Drosophila - fruit flies - Rapid development, small genome size, developmental mutants
Zebrafish
African clawed toad
Mice
Chicks
Embryonic development in Xenopus
Cleavage - cell division in early embryo
Gastrulation - Cell movements that form gut and 3 primary germ layers
Morula -> Blastula -> 2-layered gastrula and 3-layered gastrula
Name layers in 2-layered gastrula
Endoderm
Ectoderm
Name layers in 3-layered gastrula
Endoderm
Ectoderm
Mesoderm
Archenteron
Blastopore
Describe cleavages in early Xenopus embryonic development
Cleavage 1 and 2 - Perpendicular, equal holoblastic, nuclei are displaced ‘animal ward’
Cleavage 3 - Perpendicular, equatorial, Unequal holoblastic
What does cleavage 3 give more rise to?
More rapidly dividing animal pole
2 functions of gastrulation in xenopus
Forms gut
Forms primary germ layer
Bastula with blastocoel -> Blastopore -> Gut, anus, mouth
What are the primary germ layers
Ectoderm
Mesoderm
Endoderm
Endoderm in vertebrates vs insects
Gut, liver, lungs of vertebrates
Gut of insects
Mesoderm in vertebrates vs insects
Skeleton, muscle, kidney, heart, blood in vertebrates
Muscle, heart, blood in insects
Ectoderm in vertebrates vs insects
Vertebrates: skin, nervous system
Insects: Cuticle, nervous system
Explain vertebrate eyes
- Begin as pair of diverticula from lateral aspects of forebrain
- Develop to optic cup - form retina
- Invaginated ectoderm forms lens
- Overlying ectoderm forms cornea
How can signals be induced?
Vesicle in cell 1 diffuses signal molecules across the membrane where they bind secondary messengers on surface of cell 2
Ligand on cell 1 directly binds receptor on cell 2
Give some examples of signalling pathways in development
TGFbeta receptors - a/p axis specification
RTKs - Migration and proliferation
Wnt receptors - parasegment boundaries
Hedgehog receptors - limb development
Notch - Cell fate decision in CNS
Explain French flag model of morphogens
Cell has potential to develop as blue, white or red
Position defined by concentration
Positional value interpreted by cells that differentiate to form a pattern
What is AER?
- required for limb outgrowth
- Secretes fibroblast growth factors (FGFs) family proteins
What is ZPA?
- Controls anterior-posterior digit formation via induction
Induction in limb development
Donor limb bud has ZPA -> new ZPA on host limb bud
What induces mirror image formation
Shh cells implanted into anterior of developing limb bud
Two-way induction in kidney development
Ureteric bud has epithelium and mesenchyme
mesenchyme induces bud branching
Forms collecting ducts and developing renal tubules
What enzyme family is required for kidney development
RETs (type of receptor tyrosine kinase)
What is secreted by the mesenchyme?
GDNF
Ret and GDNF expressed on ureteric bud
