Mesoderm

Question 1

chick mesoderm developmenent

Answer 1

• central midline (Hensons node) structures develop
• increasing lateral and varying mesoderm tyoes further from the midline

Question 2

Frog Mesoderm formation

Answer 2

• ventral structures form further away from the midline
• folding and cutting the chick embryo resembles the frog embryo = illustrating shared pattern of the dorsal-lateral meso dedifferentiation

Question 3

Paraxial mesoderm

Answer 3

location: beside the neural tube and notochord

formation: initially forms a flat structure (segmental plate) and develops into somite’s though segmentation

Question 4

Somites

Answer 4

function:
provide positional information for embryos and differentiate into specific structures

• vary in number across vertebrates and are highly regulated by genes

Question 5

Paraxial Mesoderm Processes

Answer 5

EMT and MET

Question 6

Gene Regulation

Answer 6

Pax3:
defines paraxial mesoderm and somites

Tbx6:
- induces paraxial mesoderm
- inhibits neural tissues by suppressing sox 2

Sox2:
- specifies neural tissue
- inhibition of tbx6 can lead to the formation of additional neural tubes

Question 7

BMP inhibition via ?

Answer 7

Noggin
Follistatin
Chordin

= promotes Pax3 Expression

Question 8

Gastrulation

Answer 8

Establishes dorsal axis and patterns (A-P) axis with gradients of retinoic acid, Fgf8, and Wnt3a

Question 9

Hox Genes

Answer 9

• determines positional identity of somites
• positional fate is established before segmentation
• highly conserved across species

Question 10

Segmentation Timing

Answer 10

Controlled by Oscillating gene expressions
- Notch
- Hairy1
- ephrin ligand and receptor

Question 11

Notch

Answer 11

Activates Ephrin receptor

Question 12

Hairy 1

Answer 12

Activates Ephrin ligand in posterior somites

Question 13

What drives somite separation?

Answer 13

repulsion between cells and extracellular matrix

Question 14

Differentiation of Somites (3 cell types)

Answer 14

Dermatome: forms dermis (wnt sognalling)

Myotome: Forms muscle (wnt signalling and TF’s like myoD)

Sclerotome: forms cartilage and bones (shh signalling)

Question 15

Muscle Formation

Answer 15

Wnt Signalling regulates adhesion molecules for muscle cell aggregation
- cadherins
- integrins

Question 16

intermediate mesoderm

Answer 16

• Defined by Pax2
• forms kidneys and gonads
• requires proximity to the notochord for pax2 expression

Question 17

Lateral Plate mesoderm

Answer 17

• Forms limb bones (high BMP levels required)
• splanchnic mesoderm (anterior part) forms cardiac muscle, requiring inhibition of Wnts and BMPs

Question 18

summary of signalling and Gradients

Answer 18

• BMP levels determine mesoderm differentiation:
  1. high BMP = lateral plate mesoderm
  2. low BMP = intermediate/paraxial mesoderm
• RA and Fgf/ wnt gradients provide positional information, activating Hox Genes
• inhibition of BMP and Wnt signalling in specific regions enables the formation of specialized structures like the heart (anterior ventral region)

Question 19

what is critical for proper mesoderm differentiation?

Answer 19

• segmentation and positional information

Question 20

what gives rise to somites? and what do they differentiate into?

Answer 20

Paraxial mesoderm gives rise to somites, which differentiate into muscles, dermis, and bones

Question 21

what tightly regulated the development of intermediate and lateral plate mesoderm?

Answer 21

Gradients and Gene Expressions