Patterning the vertebrate body plan Flashcards
What is the neural plate
Group of cells from which all neural tissue is derived from
In drosophila, what is the role of Dpp and Sog
Dpp and Sog dictate the dorsal and ventral sides of the developing body plan - Sog binds to Dpp and prevents it from therefore binding to Dpp receptors
This in turn causes surrounding cells to acquire a neural identity - neural cells develop in regions where Dpp is inhibited
What is the vertebrate homologue of Dpp
BMP4
What is the vertebrate homologue of Sog
Chordin
Where are BMPs found in vertabrates
On the ventral side - chordin dorsal
What is the key difference between vertebrates and invertebrates developing neural tissue
In invertebrates - single neuroblasts are formed from the delamination of surface ectoderm - go on to form neurons in small clusters (ganglia)
In vertebrates - Sheets of cells on the dorsal side of the embryo are induced to a neural identity - formation of the neural plate - this then rolls up to form the neural tube (neurulation)
What is the specialised type of mesoderm that forms in the Xenopus oocyte
Spemann’s organiser
What transcription factors are produced by Spemann’s organiser
Goosecoid, Xnot and Xlim
What BMP antagonists are produced as a result of the specialised transcription factors
Noggin, Chordin, Cb
How do Noggin, Chordin and Cb interact with BMP
Bind with a higher affinity than BMP to its receptors blocking its action
Also bind to BMP itself causing a conformational change in the protein - no longer can bind to receptor
Where is BMP action inhibited
Entirely inhibited in the dorsal region of the embryo
What will the inhibited cells go on to produce
Neural plate - surrounded by ectoderm that wasn’t exposed to BMP antagonists and remain as surface ectoderm
How do chicks and humans develop differently
Chick embryos are a flattened disc known as a blastodisc
What is the name of the specialised region of cells that secretes BMP antagonists in the chick embryo
Henson’s Node
Where does Henson’s node develop
At the anterior end of the primitive streak
What did Spemann’s experiments on newts show
Grafted the organiser from one newt embryo and grafted it onto the ventral side of another newt embryo
This induced a second body axis and second nervous system derived from the host cells ectoderm
Indicates that signals from the grafted tissue were sufficient to induce the host tissue to acquire a neural fate
Also provided the first evidence that Spemann’s organiser will differentiate into axial mesoderm which gives rise to the notochord
How were BMP antagonists discovered
Through interrogating mRNA in organiser cells and looking for a transcript that would mimic the organisers ability to induce a secondary neural plate
What are three features of a neural inducer
- Must be expressed in the organiser
- Overexpression at an ectopic site will cause the generation of a second body axis
- KO should prevent axis formation
