Developmental Neurobiology

Question 1

What are three critical events in neural development? (also areas where things go wrong)

Answer 1

• neurulation (by 4 weeks)
• segmentation and cleavage (8 weeks)
• proliferation and mirgration (8wks - birth…and even into infancy)

Question 2

What happens during neurulation?

Answer 2

• differentiation (neuroectoderm and neural crest)
• axes of symmetry (head, ass, front, back)
• signal molecular gradients

Question 3

What event triggers formation of dorsoventral axis?

Answer 3

closure of neural tube

Question 4

What contributes to dorsoventral patterning?

Answer 4

Chemical gradients, sonic hedgehog and BMPs

Question 5

What segments are formed from neural tube from segmentation?

Answer 5

1. prosencephalon - hind brain (telencephalon, diencephalon)
2. mesencephalon (midbrain)
3. rhombencephalon (metencephalon/pons, myelencephalon/medulla)

Question 6

What happens during the proliferation and migration phase?

Answer 6

• evolution of computational capacity
• neuroectodermal precursors
• migration

Question 7

Defect in ANTERIOR neuropore results in….

Answer 7

anencephaly (MOST SEVERE FORM…not compatible with life)

encephalocele (brain inside sac coming out of head)

Question 8

defect in POSTERIOR neuropore

Answer 8

meningomyelocele (spinal cord in sac, much worse)
meningocoele (just CSF in sac)
spina bifida occulta (posterior elements of vertebrae haven’t fused…not the worst thing that can happen)

Question 9

What are risk factors for neural tube defects?

Answer 9

Valproate (for seizure)
Retinoic acid (acne)
folate deficiency

Question 10

What is the Arnold Chiari malformation?

Answer 10

Kind of between neural tube and segmentation defect
Brainstem doesn’t really form correctly (segmentation part)
Bulging

Question 11

Dandy Walker malformation

Answer 11

blockage of sites where CSF flows out of ventricle…CSF blows out into cerebellum

Question 12

Defects of segmentation results in what spectrum of defects?

Answer 12

holoprosencephaly

Question 13

Describe holoprosencephaly

Answer 13

spectrum of disorders ranging from ok to severe, associated with trisomy 13 Patau’s and trisomy 18, also sonic hedgehog…sporadic

Question 14

Mildest form of holoprosencephaly?

Answer 14

lesion in arrhinencephaly = absence of olfactory bulbs and tracts

Question 15

cyclopia

Answer 15

single eye facial defect resulting in bad hemispheric cleavage

Question 16

Defects in proliferation and migration can result in…

Answer 16

lissencephaly and polymicroglia

Question 17

lissencephaly

Answer 17

aka “smooth brain”

neuronal migration disorder, mental retardation associated with seziures, several genetic etiologies

Question 18

polymicroglia

Answer 18

many small gyri, microscopically abnormal