Lectures 29-30: Developmental Biology
- Created by: annie.edge
- Created on: 05-04-16 19:42
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- Developmental Biology (Lec. 29/30):
- How does a single cell become a complex multicellular organism?
- Proliferation: incr. cell number
- Apoptosis: selective cell death, ex. to form hands
- Differentiation: change cell identity, i.e. which genes/ level of expression
- Due to genetic lineage of cell
- Due to environment of cell
- Differentiate due to signalling molecules
- Ex. Xenopus (frog embryo) and activin signalling molecule
- Activin can bind receptors locally or distally, phos. activates SMAD dimer which binds specific DNA promoter sequences
- Expression of genes is dose-dependent; for different activin amts, the xenopus blastomere formed skin, heart muscle, blood, etc.
- Activin found in vegetal cells
- Ex. Xenopus (frog embryo) and activin signalling molecule
- Differentiate due to physical environment, ex. substrate, pH, temp
- Differentiate due to signalling molecules
- Morphogenesis: change cell shape/ physics
- Ex. Mouse embryo development
- 1. 8-cell embryo forms polarity and divides, forming a 16-cell outwardly-polar, inwardly-apolar embryo
- 2. Blastocyst: cavitation of inside material
- ICM and TE differentiate here by Cdx2 (homeobox gene) expression
- Cdx2 is necessary to form TE, without which the ICM cannot hatch out of the zona to implant in uterus
- ICM and TE differentiate here by Cdx2 (homeobox gene) expression
- 3. Inner cell mass (ICM) separates to one side of the cavity, surrounded by trophectoderm (TE)
- ICM becomes embryo
- TE becomes placenta
- 4. Primitive endoderm (PrE) forms, hatches from zona, implants in uterus
- 5. Post-implantation: proximal-distal polarity determined by distal visceral endoderm (VE) cells
- VE cells secrete nodals (similar to activin signals) to migrate up the side of embryo
- Polarity changes from prox-dist to anterior-posterior
- VE cells secrete nodals (similar to activin signals) to migrate up the side of embryo
- 6. Anterior VE expresses inhibiting signals to induce head formation genes
- Ex. Mouse embryo development
- Migration: change cell location
- How does a single cell become a complex multicellular organism?
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