Mesoderm segmentation

Question 1

Which direction does the primitive streak FIRST develop in?

Answer 1

Anteriorly

Question 2

Which tissues etc do the somites give rise to?

Answer 2

Cartilage and bone

Question 3

Which direction does mesoderm segmentation occur in?

Answer 3

Anterior to posterior fashion

Question 4

What is the tissue called before it forms somites?

Answer 4

Presomitic mesoderm

Question 5

What is the clock and wavefront mechanism?

Answer 5

Clock ‘ticks’ in posterior presomitic mesoderm-> wave front passes thru psm until it hits boundary between somites and psm-> these cells receive a signal in the form of oscillating gene expression-> commits them to form a somite

Question 6

What signalling is involved in boundary formation? And what do boundary cells do?

Answer 6

Notch signalling

Boundary cells instruct anterior cells to form a boundary

Question 7

Which 2 opposing gradients positions the determination front?

Answer 7

Retanoic acid

FGD

Question 8

Which 2 signals initiate the wave front?

Answer 8

C-hairy 1

Lunatic fringe

Question 9

What does notch activation do?

Answer 9

Down regulates notch ligands (delta)

Question 10

What is somitogenesis?

Answer 10

Epithelialisation of somites

Question 11

When does somite formation occur in regards to FGF/WNT?

Answer 11

When FGF/Wnt falls below a threshold level