Invertebrate models - Sea Urchin and C. Elegans Flashcards
Invertebrate models
Sea Urchin - large number of embryo, experimental manipulation
Genetic models - breeding done in lab
Genes within genome can altered to study effect on development
Caenorhabditis Elegans (Round worm) - can modify genome easily to see effects on development either add or remove genes
Drosophila melanogaster (Fruit fly)
Sea urchins
Are Echinoderms “Spiny skin”
Ech are Deuterostomes means mouth is formed secondarily
External fertilisation, easy to study
Only 60 days to sexual maturity, good for research
Mosaic model of development
Proposed by Weissman
Variation of this where cytoplasmic determinants control cell fate
Regulative model of development
Alternative to mosaic
Proposed by Dreisch
If determinants were present one wouldn’t get a normal embryo from a single blastomere
Cells divide their fate based on cell to cell communication
Complexity develops gradually from simpler structures
Ideal characteristics for ease of genetic analysis
Small organism - because of need to keep large numbers
Large batches of embryos
Short generation time
Easy to breed
Easy scoring of phenotypes
Sequenced genome
Caenorhabditis Elegans
Very simple organisms
Can be frozen then thawed and survive - great for research (especially if you get busy with other things)
Has stereotypical cleavage pattern - first cleavage is asymmetric
Every single worm is the same so worked out exactly what each cell will divide into
Lineage may be invariant but cell fate is not absolutely determined - experimental manipulation can change fates
Made of 1090 cells but 131 are programmed to go through apoptosis
C. Elegans and mosaic development
Lineage may be invariant but cell fate is not absolutely determined - experimental manipulation can change fates
If there was MD cells would carry on doing what meant to do, that doesn’t occur cells adapt to new place to create functioning embryo
Apoptosis
In MCO cells sometimes actively removed
Happens during development and essential in variety biological Processes in adults
Highly controlled process
Essential from proper development
- Formation reproduction organs
- Skin between digits
- Immune system maturation
Essential for homeostasis
- Mitosis/apoptosis to maintain constant number of cells
- Removal of damaged cells - DNA damage, Viral infections
Improper regulation of apoptosis can lead to disease
- Autoimmune disease
- Cancer
C. elegans and apoptosis
Apoptosis occurs highly stereotyped manner - allowed for efficient genetic dissection of process in the organism
In C. pathway/genes required for process first identified using genetics and the molecularly
RNA interference (RNAi)
Powerful mechanism to control flow of genetic information
- Double stranded RNA triggers biochemical process that degraded identical mRNAs
Discovered while studying muscle development in C. Elegans
Genome-wide siRNA libraries targeting every gene in genome
Principle of RNAi used basis at least 3 current medicines where these is faulty protein messing with cell, medicine targets and treats
Sea Urchin summary
Mainly historic
Use as model allows embryo manipulation
Contributed to understanding basic principle of development
C. Elegans summary
Worm amenable to genetic analysis and physical manipulations
Embryo has invariant cell lineage, but not fully determined
Adult worm has 959 somatic cells, individually identifiable
Gene products distributed asymmetrically at each cell division in embryo
Allowed first molecular understanding of apoptosis
Detailed molecular dissection of RNA interference (RNAi)
