Ontwikkelingsbiologie en genetica 2021
HC 1 – Developmental Biology and Genetics – Introduction
Different processes during development
- Cell proliferation
- Differentiation
- Migration
- Morphogenesis
- Growth
- Cell death
- Homeostasis
Totipotent cells = cells uncommitted to any cell
fate. Totipotent proliferating cells become post-mitotic differentiated cells.
Genetic epistasis analysis = where you try to identify in what order genes are active. A way
to do that is to make double mutant combinations. You combine two mutants that are
opposite (opposite good chance they act in the same process)
Modelorganismen:
- C. elegans neural development
- Zebrafish organ development
- Mouse forward genetics aren’t done. Reverse genetics are very efficient in mice
- Drosophila very easy to grow and cheap
Stemcells = cells that differentiate, but they are also capable of self-renewal.
- Totipotent cells = can become everything
- Pluripotent = can become a large number of things (f.e: Inner Cell Mass cells of the
blastoderm, aka ES cells)
Asymmetric divisions promote cell diversity and
support maintenance of tissue-specific stem cells.
All cells have an identical genome. How do cells
become different from each other?
- Each cell uses a different part of the
genome. Dependent on the part that you
use, gives the cell their cell fate.
How does the cell control which part it uses?
- Transcription factors, co-repressors, co-
activators (which part of the genome do
you turn on or off)
- Gene silencing (epigenetics, chromatin, small RNA’s)
- Posttranslational modifications (phosphorylation, acetylation…)
- RNA processing (splicing, nuclear export)
1
,C. elegans is a simple animal, has efficient genetics, is transparent
(so you can see the cells divide) and the cell lineage is entirely
known. In 3 days, it goes from an egg to an adult.
The C. elegans has two sexes: hermaphrodites and males.
1. The hermaphrodite first develops as a male and produces
sperm,
2. Which it stores in spermathecae pockets.
3. And then the animal switches and it produces oocytes.
4. This way it can fertilize itself.
Germline is special tissue:
- Maintenance of the totipotent state: all
cells and tissues of the next generation
develop from germ cells. Germline gives
rise to totipotent zygote
- Special cell cycle control: alteration
between mitotic and meiotic cell division
- It is immortal. Germ cell DNA can be
transmitted forever: it has an extra
maintenance of genetic integrity
efficient DNA repair pathways,
suppression/silencing of foreign DNA.
Stemcell, germcell and somatic gonad formation
Most germ-precursor cells are in meiosis I
prophase
The DTC is needed for maintenance of the
mitotic stem cell population (if DTC is gone,
the cells go to meiosis)
Mutants (LOF) in:
- LAG-2
- GLP-1
- LAG-1
Give: No proliferating germ stem cells and
premature initiation of meiosis
Mutant (gain of function) GLP-1 gives only proliferating mitotic cells in the whole C. elegans
Making a double mutation gives you answers about the order of a signal transduction
pathway (in a lineair pathway). For example:
- Mutant A zorgt ervoor dat het licht aan gaat.
- Mutant B zorgt ervoor dat het licht uit gaat.
Op basis hiervan heb je twee opties:
- A ---| B licht aan
- B A ---| licht aan
Nu maak je een dubbele mutant: Mutant AB. Deze zorgt dat het licht uit staat. Hierdoor
weet je dat de eerste optie de juiste is (omdat de activator B daar weg wordt gehaald).
2
, The pathway
- GLP-1 is a Notch-like receptor.
- LAG-2 is the ligand.
- LAG-1 is a trancriptionfactor in the nucleus
Gld-1 and gld-2 double loss of function also creates a
germline tumor phenotype (but only when you lose the
function of these two genes at once). That gives us this
pathway
So:
- inhibition of GLD-1 by GLP-1 leads to spatial
regulation of GLD-1 and meiosis.
- Positive feedback promotes the rapid transition
zone
GLD-1 = KH Domain RNA binding Protein. It is an mRNA translational repressor. Many target
mRNAs are repressed by GLD-1, including glp-1 and cye-1 cyclin E mRNA, which induce
proliferation.
GLD-2 = poly-A RNA polymerase. It stabilizes target mRNA’s.
3
HC 1 – Developmental Biology and Genetics – Introduction
Different processes during development
- Cell proliferation
- Differentiation
- Migration
- Morphogenesis
- Growth
- Cell death
- Homeostasis
Totipotent cells = cells uncommitted to any cell
fate. Totipotent proliferating cells become post-mitotic differentiated cells.
Genetic epistasis analysis = where you try to identify in what order genes are active. A way
to do that is to make double mutant combinations. You combine two mutants that are
opposite (opposite good chance they act in the same process)
Modelorganismen:
- C. elegans neural development
- Zebrafish organ development
- Mouse forward genetics aren’t done. Reverse genetics are very efficient in mice
- Drosophila very easy to grow and cheap
Stemcells = cells that differentiate, but they are also capable of self-renewal.
- Totipotent cells = can become everything
- Pluripotent = can become a large number of things (f.e: Inner Cell Mass cells of the
blastoderm, aka ES cells)
Asymmetric divisions promote cell diversity and
support maintenance of tissue-specific stem cells.
All cells have an identical genome. How do cells
become different from each other?
- Each cell uses a different part of the
genome. Dependent on the part that you
use, gives the cell their cell fate.
How does the cell control which part it uses?
- Transcription factors, co-repressors, co-
activators (which part of the genome do
you turn on or off)
- Gene silencing (epigenetics, chromatin, small RNA’s)
- Posttranslational modifications (phosphorylation, acetylation…)
- RNA processing (splicing, nuclear export)
1
,C. elegans is a simple animal, has efficient genetics, is transparent
(so you can see the cells divide) and the cell lineage is entirely
known. In 3 days, it goes from an egg to an adult.
The C. elegans has two sexes: hermaphrodites and males.
1. The hermaphrodite first develops as a male and produces
sperm,
2. Which it stores in spermathecae pockets.
3. And then the animal switches and it produces oocytes.
4. This way it can fertilize itself.
Germline is special tissue:
- Maintenance of the totipotent state: all
cells and tissues of the next generation
develop from germ cells. Germline gives
rise to totipotent zygote
- Special cell cycle control: alteration
between mitotic and meiotic cell division
- It is immortal. Germ cell DNA can be
transmitted forever: it has an extra
maintenance of genetic integrity
efficient DNA repair pathways,
suppression/silencing of foreign DNA.
Stemcell, germcell and somatic gonad formation
Most germ-precursor cells are in meiosis I
prophase
The DTC is needed for maintenance of the
mitotic stem cell population (if DTC is gone,
the cells go to meiosis)
Mutants (LOF) in:
- LAG-2
- GLP-1
- LAG-1
Give: No proliferating germ stem cells and
premature initiation of meiosis
Mutant (gain of function) GLP-1 gives only proliferating mitotic cells in the whole C. elegans
Making a double mutation gives you answers about the order of a signal transduction
pathway (in a lineair pathway). For example:
- Mutant A zorgt ervoor dat het licht aan gaat.
- Mutant B zorgt ervoor dat het licht uit gaat.
Op basis hiervan heb je twee opties:
- A ---| B licht aan
- B A ---| licht aan
Nu maak je een dubbele mutant: Mutant AB. Deze zorgt dat het licht uit staat. Hierdoor
weet je dat de eerste optie de juiste is (omdat de activator B daar weg wordt gehaald).
2
, The pathway
- GLP-1 is a Notch-like receptor.
- LAG-2 is the ligand.
- LAG-1 is a trancriptionfactor in the nucleus
Gld-1 and gld-2 double loss of function also creates a
germline tumor phenotype (but only when you lose the
function of these two genes at once). That gives us this
pathway
So:
- inhibition of GLD-1 by GLP-1 leads to spatial
regulation of GLD-1 and meiosis.
- Positive feedback promotes the rapid transition
zone
GLD-1 = KH Domain RNA binding Protein. It is an mRNA translational repressor. Many target
mRNAs are repressed by GLD-1, including glp-1 and cye-1 cyclin E mRNA, which induce
proliferation.
GLD-2 = poly-A RNA polymerase. It stabilizes target mRNA’s.
3
