Transcript Endogenous siRNA pathways in C.elegans

Caenorhabditis elegans
Quite a nifty li’l worm.
The Basics
C. elegans is a small worm
one millimeter long. There are
two sexes, a male and a self
fertilizing hermaphrodite. Its
inner workings are similar to a
human’s, which is part of the
reason its considered a model
organism.
Widely studied, C. elegans is a
popular test subject among
neurology researchers and has
had many papers published on
it in an array of of topics.
Currently there are 342 papers
listed under PubMed for C.
elegans.
Who sequenced it? The Sanger Institute and Washington
University.
When? While research on C. elegans began 1968 by
Sydney Brenner, its genome wasn’t published until
1998 and not fully complete until 2002.
Why?
Research began on C. elegans because of interest its
nervous and developmental systems, as they are
very similar to humans. It is still being used in
research for these same reasons.
Because C. elegans is a
eukaryote it contains a
nucleus. Within that
nucleus are 6 chromosomes
that contain a total of
100,000,000 base pairs
with roughly 19,800 genes.
A related organism, C.
briggsae, is in the process of
being sequenced. These two
are often compared to each
other for reference.
Ribonucleic acid (RNA)
RNA vs. DNA
RNA-world hypothesis
RNA species
-messenger RNA (mRNA)
-transfer RNA (tRNA)
-ribosomal RNA (rRNA)
-catalytic RNA (ribozymes)
-small interfering RNA (siRNA)
-ncRNAs (miRNA, tncRNA,piRNA...)
rRNA
www.contexo.info/DNA_Basics/Protein_synthesis.htm
Gene silencing by dsRNA
unc-22
dsRNA
control
progeny of injected worm
RNA interference (RNAi)
• The Nobel Prize in Physiology or Medizine 2006 for Craig Mello
and Andrew Fire for their discovery of RNAi in C.elegans
nobelprize.org
RNAi mechanism in C.elegans:
basic scheme
less mRNA, less protein = gene silencing
RNAi
• conserved mechanism (at least 1 000 000 000 (=thousand billion) years old)
• roles
–
–
–
–
primitive immune system
gene regulatory mechanism (via mRNA destruction)
chromatin remodelling (via histone modifications)
DNA elimination (in Tetrahymena thermophila)
• tool
– functional genomics
– potential for pharmaceuticals