Cardiac Development

Question 1

Sections of mesoderm (medial to lateral)

Answer 1

Chordomesoderm

Paraxial mesoderm

Intermedial mesoderm

Lateral plate mesoderm

Question 2

Lateral plate mesoderm

Answer 2

• Anterior region forms the heart
• Posterior region forms blood
• Lateral/ventral forms myocardium

Question 3

Foregut

Answer 3

Foregut endoderm is beneath and signals to induce cardiac mesoderm

Question 4

Cardiac Crescent

Answer 4

• First morphologically identifiable cardiac structure

- Transforms to linear heart tube

Question 5

Folding (22d)

Answer 5

• Tubular structure formed of endocardium and myocardium
• Myocardium and foregut are connected by dorsal mesocardium
• Connection is lost by apoptosis and only VA poles stay connected

Question 6

Looping

23-4d

Answer 6

• V pole move anteriorly to meet A pole
• IFT and OFT fuse
• Chambers begin to form
• Valve precursors allow unidirectional flow

Question 7

Septation (35d)

Answer 7

• Two layers of myocardium:
  Trabecular (primitive)
  Compact (more advanced)
• Right and left side are separated

Question 8

Gastrulation

Answer 8

• Epiblasts migrate inside from the primitive streak through a slit-like structure following nodal signals
• FGF8 repels them, FGF4 attracts them
• They can become mesoderm or endoderm

Question 9

Tinman/Nkx2.5

Answer 9

• Induced by BMP2
• TF that induces expression of genes in early heart field cells
• Expressed throughout entire mesoderm initially
• As mesoderm moves dorsally, expression is stronger at one pole

Question 10

Foregut-derived inducers

Answer 10

• BMPs
• FGFs
• Shh
• Crescent

Question 11

Ectoderm and notochord

Answer 11

• Release antagonists to prevent heart formation in other regions

Question 12

The Second Heart Field

Answer 12

• Cells must migrate in to help the heart grow as FHF-derived cells do not proliferate much
• Precursors of RV and common OFT migrate
• RV entirely derived from SHF cells instructed by dHAND/Hand2

Question 13

Define the First Heart Field

Expression

Answer 13

• The first wave of mesodermal cells that differentiate to form the initial heart tube. Origin of the LV.
• Express muscle-specific proteins (MLC2A/3F)
• First group to down-regulate Isl1

Question 14

Define the Second Heart Field

Answer 14

• Progenitors added to the formed heart tube at the A or V pole

Question 15

Define the Anterior Heart Field

Expression

Answer 15

• A region derived of the SHF restricted to the RV and OFT myocardium progenitors
• FGF10-LacZ