Somitogenesis and limb development
Somitogenesis
Somites form from unsegmented mesoderm.
Here we look at chicken embryo in different
stages from the dorsal view.
A. Earlier stage, not much to be seen
besides the node and some primitive
streak.
B. Here you can start to see something,
beginning of the somites
C. Here you start seeing the somites.
Look at different dissections:
- Primitive streak
- Epiblast → ectoderm
- Endoderm
- Migrating mesodermal cells → EMT
- Paraxial mesoderm
- We are above the node → see full picture of embryo above
- Somites
- Somatic mesoderm
This is what it looks like in a schematic way. Look at primitive streak and
direction of elongation.
1
,Here we look at the development of the mesoderm:
We talk about the paraxial mesoderm and
specifically the somites today.
Who becomes who?
This part of somites gives rise to the muscles in the limbs.
2
, Traditional view is how it was viewed back then, but now we know more!
Somitogenesis → formation of the somites.
BrdU-staining = cell proliferation (methods!!)
We do not know how left and right side somites know they have to form together as they are
physically separated.
Fibronectin → red staining of membrane.
How come the somites form → molecularly.
Looking at different expressions:
- Mesp is a target of Notch (see signalling pathway).
In situ hybridization
What different information do we get from exonic and intronic in situ hybridization?
- where mRNA is present → where the translation and protein are highly likely to also be.
- where transcription takes place
3
Somitogenesis
Somites form from unsegmented mesoderm.
Here we look at chicken embryo in different
stages from the dorsal view.
A. Earlier stage, not much to be seen
besides the node and some primitive
streak.
B. Here you can start to see something,
beginning of the somites
C. Here you start seeing the somites.
Look at different dissections:
- Primitive streak
- Epiblast → ectoderm
- Endoderm
- Migrating mesodermal cells → EMT
- Paraxial mesoderm
- We are above the node → see full picture of embryo above
- Somites
- Somatic mesoderm
This is what it looks like in a schematic way. Look at primitive streak and
direction of elongation.
1
,Here we look at the development of the mesoderm:
We talk about the paraxial mesoderm and
specifically the somites today.
Who becomes who?
This part of somites gives rise to the muscles in the limbs.
2
, Traditional view is how it was viewed back then, but now we know more!
Somitogenesis → formation of the somites.
BrdU-staining = cell proliferation (methods!!)
We do not know how left and right side somites know they have to form together as they are
physically separated.
Fibronectin → red staining of membrane.
How come the somites form → molecularly.
Looking at different expressions:
- Mesp is a target of Notch (see signalling pathway).
In situ hybridization
What different information do we get from exonic and intronic in situ hybridization?
- where mRNA is present → where the translation and protein are highly likely to also be.
- where transcription takes place
3
