Lecture 9

Question 1

What do neural tube stem cells give rise to?

Answer 1

All CNS nerve cells, astrocytes, and oligodendrocytes

Question 2

Where does neural tube stem cell replication occur?

Answer 2

Ventricular zone of neural tube

Stem cells migrate through neural tissue during replication

Daughter cells can remain to generate more progeny cells or migrate out to form neurons or glial cells

Question 3

What is neural tube stem cell replication also known as?

Answer 3

Neurogenesis

Stem cells switch to asymmetric mode of cell division

One daughter remains progenitor, other becomes neuron or glial cell

Question 4

Formation of radial glial cells

Answer 4

Neuroepithelial cells form a early radial glia by nIPC denoting intermediate progenitor cells for neurons

Late radial glia are formed from aIPC and olPC denoting intermediate progenitor cells to form astrocytes and oligodendrocytes

Question 5

Explain the anterior-posterior polarity of neural tubes

Answer 5

• Formation of neural tube does not occur all at once along its full length
• Begins in middle at embryonic day 20 in humans and then towards each end
• Openings left at each end are called anterior (cranial) and posterior (caudal) neuropores

Anterior neuropore closes on day ~25 and posterior neuropore on day ~27

Question 6

What are somites?

Answer 6

Balls of mesoderm that mature into segmented axon skeleton

Each pair added sequentially from head to tail down length of embryo

Question 7

Wnt signalling in neural patterning

Answer 7

Wnt inhibitors (dickkopf, Cerberus, Frzb, Insulin-like growth factor) are formed from dorsal anterior mesoderm and the organiser

Question 9

BMP and Wnt inhibitors in neural development

Answer 9

Chordin, Noggin and Follistatin can inhibit BMP in the formation of the spinal cord, head and brain

Dickkopf, Cerberus, Frzb, and IGF can all inhibit Wnt in the formation of the head and brain

Question 10

FGF and RA in anterior-posterior patterning

Answer 10

Fibroblast growth factor (FGF) is made at posterior and degraded at anterior

Retinoic acid (RA) made at central mesoderm

FGF, RA, and Wnt signalling all regulate Hox gene expression

Unique cocktail of Hox at each ‘segment’ specifies its anterior-posterior identity

Question 11

Gradient controlling Dorso-ventral patterning

Answer 11

TGFbeta allows for control on dorsal sensory neurons, whilst Shh allows for control on ventral motor neurons

Wnt inhibitors decrease as signals are passing, where they are greatest at beginning

Question 12

Explain brain development from the neural tube

Answer 12

• Anterior part of neural tube divides rapidly to form three primary vesicles (forebrain, midbrain, and hindbrain)
• Part of forebrain (telencephalon) curls up and around (forms cerebral cortex)
• Posterior part forms spinal cord

Question 13

What regions of the brain do the forebrain, midbrain, and hindbrain form?

Answer 13

Forebrain - Cerebral cortex, underlying white matter, corpus callosum, basal ganglia

Midbrain - Vision, hearing, motor control, sleep/wake, arousal, temperature regulation

Hindbrain:
Medulla - Deals with autonomic functions of breathing, heart rate, blood pressure

Pons - part of brainstem, relays signals from the forebrain to the cerebellum; deals with sleep, respiration, swallowing, bladder control, hearing, equilibrium, taste, eye movement, facial expressions, facial sensation

Cerebellum - Posture, balance