L9 Neuroembryology, Segmentation, Cell Proliferation

Question 1

what develops from the neural tube?

Answer 1

-Neural Tube- becomes the spinal cord

Question 2

what develops from neural crest cells?

Answer 2

-Neural Crest Cells- give rise to the dorsal root ganglia, Schwann cells, melanocytes, peripheral neurons and glia, sympathetic/parasympathetic/enteric ganglia.

Question 3

what is the role of BMP in ectoderm differentiation?

Answer 3

-Bone morphogenic protein suppresses neural differentiation and promotes epidermal tissue development.
-Hensen’s Node- releases Chordin and Noggin to block BMP; allowing neural
Development.

Question 4

what are the consequences of failed neural tube closure?

Answer 4

rostral - anencephaly

caudal - spina bifida

Question 5

what are the types of spina bifid a?

Answer 5

• Occulta – “tuft” of hair
• Meningocele – contains meninges
• Myelomenigocele – contains meninges and spinal cord
• Myeloschisis – nervous tissue with no overlying membrane → totally exposed

Question 6

what are homeotic genes?

Answer 6

• Homeobox Genes- encode transcription factors. They play a role in establishing compartmentalization and segmentation within the brain. May control the fate of many other genes and act as master genes.
  
  • Dictate Anterior-Posterior orientation in the embryo.
  • EMX- develop schizencephaly (deep crevices in the cortex)
  • OTX- epilepsy. Both are mutations in HOX genes.

Question 7

what are Hox genes?

Answer 7

• Hox genes (from an abbreviation of homeobox) are a group of related genes that control the body plan of the embryo along the anterior-posterior (head-tail) axis. After the embryonic segments have formed, the Hox proteins determine the type of segment structures (e.g. legs, antennae, and wings in fruit flies or the different vertebrate ribs in humans) that will form on a given segment. Hox proteins thus confer segmental identity, but do not form the actual segments themselves

Question 8

how does retinoic acid affect HOX gene?

Answer 8

Retinoic Acid- produced in Hensen’s node along with Chordin and Noggin.
-Activates the Hox genes (apart of homeobox genes). Establishes a gradient that allows anterior-posterior expression to occur. Gradient gives positional information.

Question 9

what is the developmental mechanism of the rhombencephalon?

Answer 9

-Krox-20/Kreisler- genes that establish the segmentation in the hindbrain. Once these boundaries are set, cells do not cross them. Similar to invertebrate neurodevelopment.

Question 10

what makes Sonic Hedgehog Protein

Answer 10

notocord (and later floor plate)

Question 11

what is Sonic Hedgehog Protein

Answer 11

Influences the ventral surface of the notochord.

• Induces notochord cells to become floor plate cells and motoneurons (ventral phenotype).
• BMP induces the cells that lie dorsally to the developing notochord.
• The produces and dorso-ventral axis for the developing nervous system.

Question 12

what do pts with abnormalities in emx develop?

Answer 12

schizencephaly - rare grey matter malformation of brain = deep cortex crevices

Question 13

what do pts with abnormalities of otx develop?

Answer 13

epilepsy

Question 14

what are the primary vesicles?

Answer 14

prosencephalon
mesencephalon
rhombencephalon

Question 15

what are the secondary vesicles?

Answer 15

telencephalon
diencephalon
mesencephlon
metencephalon
myelencephalon

Question 16

identify neuronal cellular activity at the ventricular and pial surfaces during development

Answer 16

• Cells nucleus migrates to the tube’s inner or ventricular surface, the pial end of the cell detaches, the cell divides and the nuclei of the daughters migrate toward the outer surface as the cells reattach to the surface.

Question 17

What happened in the eyeless experiment

Answer 17

• Eyeless gene in fruit flies is the master control gene for eye growth.
• When over-expressed; many eyes are developed.
• Fly reacts similarly to the eyeless gene of a mouse. (many eyes produced)
• Implies that all species came from similar genetic background.

Question 18

what happens with neuronal cellular activity at ventricular and pial surfaces during development?

Answer 18

• The nucleus of the cell migrates to the ventricular (inner) surface.
• Pial end detaches (outer part).
• Nucleus then divides and both new cells now migrate back to the pial surface.

Question 19

what is the marginal zone and the ventricular zone in the telencephalic vesicle?

Answer 19

• Marginal Zone- grey matter of the cortex. Reelin signals a cease in migration here.
• Ventricular Zone- lines the lateral ventricles.