Neural Tube Formation - Mammalian Development

Question 1

What gives rise to the neural tube? During what stage does this occur?

Answer 1

The neural ectoderm forms the neural tube during neurulation 


Question 2

Neurulation and somite formation progress from ____ to ____. Why?

Answer 2

Neurulation and somite formation progress from anterior to posterior, so that in one animal, several stages of somite formation and neurulation can be seen.

Question 3

What cell behaviors drive neural tube formation/neurulation?

Answer 3

Cell behaviors:

1. Wedging (apical constriction)
2. convergence and extension in the neural plate
3. medial migration of epidermis following from epiboly
4. touching and then fusion of the neural folds.
5. the neural tube segregates from the epidermis

These behaviors are particularly clear in the chick and the amphibian urodele embryo.

Question 4

___________ show the regions of bending in the floor plate and dorsolateral hinges.

Answer 4

Freeze fracture electron micrographs

Question 5

What morphogenetic modements lead to neural tube formation?

Answer 5

1. The neural plate narrows, by the convergent extension of cells to the midline.
2. This brings the folds closer together, so that the folds can reach each other and fuse
3. The convergence and extension relies on cells being able to orient their behavior in the plane of the tissue.

Question 6

What proteins/genes foes PCP pathway use?

Answer 6

Planar cell Polarity (PCP) pathway uses upstream components of the Wnt signaling pathway, including Dishevelled, and diverges to use different proteins downstream, such as the Strabismus/VanGogh protein (Vangl in vertebrates).

Question 7

Mutations in the Vangl genes cause _______

Answer 7

a failure of the neural tube to close in spina bifida.

Even heterozygous mutations cause defects in some C/E processes, for example in the inner ear where there is a precise arrangement of sensory cells, and mutations in C/E components often cause deafness.


Question 8

What cells become apically constricted? How?

Answer 8

the cells at hinge points become wedge shaped, by apical constriction.

in the neural plate requires the expression of the shroom gene that mediates apical constriction in epithelial cells.

Question 9

Shroom -/-

Answer 9

neurulation fails

Question 10

Changes in cell adhesion contribute to the segregation of tissues. This is mediated by _______

Answer 10

Cadherins