3. VL Flashcards
C. elegans I C. elegans: cell lineage, signal transduc2on and programmed cell death
Caenorhabdis elegans is a …. and was first described in …. by….
roundworm; 1900; Emile Maupas
Advantages of the model organism
- Benign for humans.
- Optical transparency.
- Organogenesis/physiology: „in miniature“
- Many protocols established: mutagenesis, transgenesis, molecular biology,..
- Easy to breed and maintain.
- Small size (approx. 1 mm long and 40 μm wide).
- Rapid life cycle (3-3.5 days).
- Large brood size
- Can be frozen and stored at -80°C for more than 10 years.
Facts about C. elegans
Six chromosomes (linkage groups): 5 autosomes I-V, 1 sex chromosome X - containing 20.444 protein-coding genes Two genders: Hermaphrodites, Males Hermaphrodites: Selffertlization, Egg and sperm from same animal -> Offspring clones - no variation
What do you know about the genetics in C. elegans?
- First multicellular eukaryoic organism with a fully sequenced genome (1998).
- 38% of C. elegans protein coding genes have predicted orthologs in the human genome.
- Invariant development.
- Constant cell numbers
Limitations of that model organism
- Small size.
- Dissection almost impossible
- No cell culture lines exist.
- Not all metazoan genes are found in C. elegans genome.
What tissues owns an adult hermaphrodite C. elegans?
Pharynx, Uterus, proximal gonades, distal gonades, intestine, anus
How is the somatic muscle built up?
type: striated (gestreift)
95 diamond shaped body-wall muscle cells
4 quadrants run along side the length of the animal lead to the sinusoidal movement of the animals
C. elegans: model for… (diseases)
Duchenne’s Muscular Dystrophy (DMD) and cardiomyopathies.
Mutation in dystrophin caused DMD
C. elegans: the intestine - what do you know? How is it built up?
- 20 large epithelial cells form a long tube around the lumen.
- only fixed to pharynx and rectum.
- only one associated muscle at the posterior end.
- not directly innervated.
What functions have the intestine of C. elegans?
- digestion of food
- absorption of processed nutrients
- synthesis and storage of macromolecules
- initiation of an innate immune response to pathogens
- nurturing of germ cells by producing yolk
the intestine of C. elegans is a model for…?
- organogenesis
- morphogenesis
- cell fate (pharynx)
- infection and response to infection (intestine)
What is the C. elegans excretory system a model for?
for tube formation
What do you know about the C. elegans - nervous system?
- Hermaphrodites 302 neurons / males 382 neurons.
- Mostly simple structure with one or two neurites exiting from the cell body.
- Passive nerve conduction: No sodium-dependent action potentials. High membrane resistance.
- Various neurotransmisers and receptors involved.
- Multi-functional neurons (polymodality), probably because of the low number.
C. elegans - nervous system is an important model for…
…Neurobiological questions
< 7000 chemical synapses & gap junctions connections
• connectome (Gesamtheit der Verbindungen des Nervensystems) known
–> Cell Lineage studies!
For what is the reproduction system of. C. elegans a model?
- morphogenesis
- sex-specific anatomy
- programmed cell death
How are male mating and self mating differ from each other?
- Selfing: approx. 300 progenies
* Mating: approx. 1000 progenies (male sperms preferred)
Where can you find information about C. elegans in the web?
Wormbook (anatomy), wormbase (genetics), wormatlas (anatomy), Caenorhabdi2s Genetics Center (wildtype and mutants)
Topic: Mutagenesis: what mutations are happening spontaneously and what are they caused by?
point mutation, gene duplication, deletions
caused by: repair errors, endogenous oxidative damage, exogenous environmental insult
What are the 3 mutagenesis strategies?
- Genome-wide mutagenesis (forwardgenetics): The whole genome is mutagenized to identify genes that are involved in a specific process, e.g. developmental or physiological.
- Target-selected mutagenesis (reverse genetics): The whole genome is mutagenized, but only a specific target gene is screed for mutations.
- Gene-targeted mutagenesis (reverse genetics): A target gene is specifically mutagenized.
C. elegans in space - what does scientists found out working on the International C. elegans first experiment - ICE-FIRST in 2004?
experiment took place in space (Strahlendosis 150 fach höher als auf Erdoberfläche) –> after 11 days no real mutations noticed –> DNA repair mechanism worked efficiently and that spontaneous alterations (Änderungen) to the genome may result from cell- intrinsic errors
What mutants of the C. elegans do you know?
uncoordinated - Unc
roler - Rol
How does “suppressor screen” works?
Chemical induced mutation –> Screening for potential signaling partners
one of the biggest discoveries in C. elegans was the study from John Sulston and Sydney Brenners about the Cell linage. What exactly did they want to find out and how did they do this?
wanted to understand the nervous system –> useful to gather knowledge about the development of the nervous system of C. elegans. Sulston started with ventral nerve cord and used differential interference contrast (DIC) optics (looked at the animals alive)
took Sequential photographs of an L1 hermaphrodite
result: found our about: complete post-embryonic cell lineage (Sulston) and later about the embryonic cell lineage
For which founding Horwitz, Brenner and Sulston got the nobel price for?
- Invariant cell divisions generate a fixed no. of progeny cells of rigidly determined fates.
- Three main events occur during post- embryonic development: Cell division, Cell migration, Cell death
