l5

Question 1

does the hypothalamus form from growth of a central Fgf10+ stem like population?

Answer 1

yes

- some form Fgf10+ progenitor and some migrate and differentiate to form a anterior or posterior/mammilary cell

Question 2

which cell surface receptors are upregulated by Glia?

Answer 2

• Hhip
• ptc1
• ptc2

(form unproductive ligand complexes - compete with productive ligand complexes)
(productive ligand complexes decrease - signal response decreases)

Question 3

which receptors are downregulated by GliA?

Answer 3

• cdo
• gas1
• boc

(less likely to activate Smo)

Question 4

what levels of Shh are needed to induce Shh itslef?

Answer 4

High levels of Shh are needed to induce Shh

Question 5

what is seen in Pm are tbx2 expression?

Answer 5

Shh begins to be downregulated in midline

• this allows the spread of Shh to neighbouring cells
• LDA tunred off in midline

(this doesnt occur in sc)

Question 6

how are genes regulated?

Answer 6

genes are regulated by multiple TFs

-TFs can act on gene enhnacers

Question 7

what happens when BMP antagonists bind to an enhancer region of neural gene?

Answer 7

neural gene is switched on / expressed in ventricular zone

Question 8

what happens when GliA HD TF binds to enhancer gene bmp antagonists bind to to activate?

Answer 8

when GLIA HD TF binds to enhancer of same gene - it is repressed

Question 9

what is the enhancer that regulate Shh hypothalamic expression?

Answer 9

SBE2 enhancer

Question 10

why might transcription of the Shh gene be different in different areas of the NS?

Answer 10

• may be different enhancer elements being activated
  (SBE2 may not be present in other areas - no mechaism to sotp LDA - why LDA cant be stopeed in SC patterning- spread is limited))

Question 11

what needs to bind to the SBE2 enhancer for Shh transcription to occur?

Answer 11

BOTH Sox2 and GliA need to bind to SBE2 enhancer

Question 12

what does tbx2 do when it binds SBE2?

Answer 12

tbx2 diplaces sox2

-Shh signalling can no longer oocur (as sox2 is no longer present)

Question 13

what induces tbx2 expression?

Answer 13

BMP7 from late prechordal mesoderm
(Shh begins to become downregulated in cells overlieing PM (as sox2 is displaced))
(LDA stops - Shh can travel to neighbouring cells)

Question 14

where do GliA and Sox2 come from in order to bind to SBE2 enhancer for Shh gene/signalling?

Answer 14

Shh and nodal from prechordal mesoderm induce GliA/Shh transcription
- Sox2 already there due to nodal