Notochord Development - Lecture 13

Question 1

Notochord Development

Answer 1

Primitive node is source of cells for notochord formation

Left behind from the regression of the primitive streak, notochordal cells fuse with flanking endodermal cells and a neuroenteric canal is formed.

They then let go and form a solid notochord

Question 2

Notochord inductive functions

Answer 2

Formation of axial structures
-shh

Superior ectoderm conversion to neural ectoderm

• Foxa-2 and Goosecoid
• Noggin and Chordin

Vertebrate body formation from some mesodermal cells of somites

Question 3

What factor is responsible for establishing the anteroposterior axis, preprimitive streak?

Answer 3

Nodal - expressed in the posterior epiblast and blocked in the anterior epiblast

Lefty and Cer 1 block nodal

Question 4

Wnt3, pre-primitive streak

Answer 4

Expressed in posterior epiblast and induces expression of nodal

Question 5

what is the function of cerebrus like transcription factor?

Answer 5

Inhibits development of posterior structures

Question 6

What transcription factors are involed with neural induction in the early primitive streak ?

Answer 6

Noggin

Chordin

Question 7

What is nodal’s role in the deveopment of the primitive streak?

Answer 7

Induces the primitive streak, which helps establish left-right symmetry

Question 8

What is the source and function of cerebrus-like and DKK-1 transcription factors? In early primitive streak stage

Answer 8

Source: anterior visceral endoderm

Inhibits development of posterior structures

DKK-1 also blocks Wnt

Question 9

what is the source and function of goosecoid? In early primitive streak stage

Answer 9

Orgin: primitive node
Effect: activates genes (chrodin/noggin)

Question 10

What is the source and effect of brachyury? In early primitve streak stage

Answer 10

Source: primitive streak
Effect: notochord formation and movement of cells through primitive streak

Question 11

What is the function of Foxa-2 early in primitive streak stage?

Answer 11

Establishment of primitive node

Intiation of notochord function

Establish midline structures cranial to node

Question 12

What is the function of shh in the prechordal plate and then in the notocord?

Answer 12

IN PRECHORDAL PLATE SHH INDUCES AXIAL STRUCTURES

IN THE NOTOCHORD SHH IS A NEURAL UNDUCER

Question 13

In late primitive streak stage what TF is responcible for normal head formation?

Answer 13

Cerebrus-related 1

Question 14

What TF are neural inducers in the late primitive streak stage?

Answer 14

Noggin
Chordin
Shh

Question 15

What is Foxa-2 function in the prechordal plate stage and notochord stage of the late primitive streak?

Answer 15

Prechordal plate: activates chordin and noggin

Notochord: same

Question 16

In the late primitve streak which TF’s activate hox genes?

Answer 16

Retinoc acid 
Wnt
FGF
Nodal
Brachyury

Question 17

When does asymmetry first show up in developemnt, which TF cause this?

Answer 17

First sign: beating of cilia around primitive node - causes a durectional current of TGF-B: Nodal and Lefty-1

Current begins in 6-8 somite stage of mouse

Nodal is swept to the left by cilary current where lefty-1 blocks diffusion back to the right.

Also involved: shh, retinoic acid and FGF-8