Anterior and posterior regionalisation Flashcards Preview

Building the nervous system > Anterior and posterior regionalisation > Flashcards

Flashcards in Anterior and posterior regionalisation Deck (16)
Loading flashcards...

What is a cells competence

The past history of the cell


Which part of the brain is formed first in development, what follows

Forebrain first, then mid and lastly hindbrain and spinal cord


How does axial mesoderm move

Involutes and extends under the midline of the newly induced neuronal plate


What would you find if you were to stop development at the point where axial mesoderm has just involuted below the midline of the neural tube - what molecular markers would there be

Expressing markers that are confined to the forebrain - when first induced - the neural plate is anterior in character


How does the posterior nervous system develop from the initial axial mesoderm

The node changes causing the notochord formation which secretes signals that cause growth and posteriorization


What is the activation - transformation model

Neural inducing molecules induce and maintain the anterior forebrain tissue. Initially come from early organiser cells but are then maintained by prechordal tissue once the organiser differentiates
Subsequently other signals then transform the tissue to a more posterior fate


What are posteriorising signals antagonised by

Prechordal tissue


Before gastrulation, what do cells in the organiser secrete

BMP/Wnt inhibitors - leads to the induction of neural tissue with an anterior character


What do the cells of the organiser secrete after gastrulation

Only the cells that involuted first continue to produce BMP and Wnt inhibitors


What three signals are posteriorising

Wnt,FGF and retinoic acid


What gradient is found in the posteriorising signals

Highest concentrations are most posterior


What does the neural plate differentiate into

Axial mesoderm - notochord and prechordal mesoderm


What is being produced in the prechordal mesoderm

Wnt inhibitors and cerberus - very strong forebrain inducing activity


What is anencephaly and how is it caused

occurs in humans where the forebrain is not maintained - due to the absence of transcription factors that maintain anterior character (Wnt inhibitors/cerberus)


How are HOX genes activated

Threshold concentrations of posteriorising signals - those expressed in posterior regions only, are only responsive to high concentrations of signals
Those that are expressed along the whole body are sensitive to low concs of posteriorising signals


How are HOX genes required in the formation of rhombomeres

In response to posteriorising signals - A HOX code is set up along the body axis, Differing concentrations/ different genes are required in the eventual establishment of hindbrain rhombomeres and the development of the cranial nerves