L5 - Anterior vs Posterior Flashcards
What three systems must be developed
ENS PNS CNS
What regions make up the forbrain
Lateral ventricle Telencephalon Neural retina Lens 3rd ventricle
What regions make up the midbrain
Mesencephalon and the cerebral aqueduct
What regions make up the hind brain
Metencephalon
Myclencephalon
4th ventricle
What layers lie under the posterior end of the neural plate
Notochord
What layers lie under the anterior end of the neural plate
Anterior endoderm
Prechordal mesoderm
What can be said about the signals from the anterior endoderm and prechordal mesoderm compared to the notochord, what does this cause
Slightly different signals
Signals from the anterior endoderm and prechordal mesoderm cause the induction of the anterior neural identity
What experiemental evidence can be obtained if developement is stopped at the instnant where the prechordal mesoderm has involuted
Look at the molecular markers can see that the neural plate expresses makers which are later confined to the forebrain
i.e. the early neural plate is anterior in character
Describe the activation-transformation model and its relevance to the determination of the posterior and anterior identities
Signals from the notochord cause cells at the back end of the neural plate to proliferate
At the same time other signals from the notochord changes these cells from an anterior to posterior identity
Anterior TFs are turned OFF
Posterior TFs turned ON
What is the activation-transformation model the basis for
The formation of the anterior forebrain and the posterior hind brain and spinal chord
What signals are involved at the anterior end
BMP antagonists and WNT antagonists
What signals are involved at the posterior end
FGFs (in a gdt highest most posteriorly)
WNTS (in a gdt highest most posteriorly)
RA (in a gdt highest most posteriorly)
Describe how RA (what does it stand for) signalling works
Retanoic acid
Small so able to diffuse into cells where it binds to a cytosolic receptor - complex RA-R able to enter the nucleus where it directly influences gene expression
Segmentation occurs as a result of
Step wise difference in the gradients of the signalling moleucles
What are the two models for segemetation by a morphogen
Alan Turing - reaction diffusion
Lewis- wolpert Postional infromation (french flag)
What does HOX stand for
Homeobox containing
Describe what the HOX genes are responsible for
Selection of a certain body area fate along the AP axis e.g. abdomen and the thorax
Describe the different genes that are involved in the segmentation of the drosophila
Gap
Pair rule
Homeotic genes
Segment polarity genes
What are the different segments of the drosophila
T1-T3 and A1-A8
T1-T3 controlled by
UBX
A1-A4 controlled by
AbdA
A5-A8 controlled by
AbdB
What causes activation of the HOX genes
Very specific threshold concentrations of posteriorising factors
How many HOX genes in humans
Why is this the case
4
Safety measure incase of mutation
What is homeobox DNA
Encodes a DNA binding protein of 60 amino acids called the homeodomain
What are the different regions of hind brain and spinal cord defined by
HOX signature
What does the RA gradient induce
Different patters of HOX transcript
What occurs in a knock out of HOXa1 and HOXb1
These genes are required to specify rhombomeres 4 and 5 and nerves that are normally made in this region
So double knockout for these genes results in a mouse that will develop without the abducens nerve
Where are the midbrain strucutres induced
At the interaction between the forebrain and hindbrain boundary
What are the three primary brain vesicles
Prosencephalon
Mesencephalon
Rhombencephalon
What does the prosencephalon give rise to
Telencephalon
Diencephalon
What does the rhombencephalon give rise to
Metencephalon
Mycelnecphalon
What does the mesencephalon give rise to
Midbrain
What does the telencephalon give rise to
Olfactory bulbs
Hippocampus
Cerebrum `
What does the diencephalon give rise to
Retina
Epithalamus
Thalamus
Hypothalamus
What does the metencephalon give rise to
Cerebellum
Pons
What does the myclencephalon give rise to
Medulla
The early ground plan for the mature NS is established by?..
Antagonistic signalling centres
