Limb Devolpment

Question 1

AER

Answer 1

Apical ectodermal ridge.

• initiates outworks growth of a limb as well as the PZ in anterior-poster and proximal-distal axes devolpment

Question 2

ZPA

Answer 2

Zone of polarity.

Used in anterior-posterior axis formation. Contains high amounts of SHH

Question 3

SHH

Answer 3

Sonic hedgehog

Prime signaling molecule in anterior- posterior limb formation

• high amounts of SHH = posterior component differentiation
• low amounts of SHH = anterior component differentiation

Question 4

FGF

Answer 4

Fibroblast growth factor

Growth factor used to initae proliferation of cells.

Used in anterior-posterior (FGF10)

Used in proximal-distal (FGF8)

Question 5

HOX genes

Answer 5

specific genes that control limb and appendage formation through apoptosis of of mesnechymal cells

• play key role in proximal-distal limb devolpment

Question 6

BMP

Answer 6

Bone morphogenic protein

• used in seperation of digits by synergistic signals from SHH and BMP

Question 7

Wnt7a

Answer 7

Used in ventral-dorsal axis formation.

Congregates around the dorsal ectoderm and generates dorsal differentiation

Question 8

EN-1

Answer 8

Used in dorsal-ventral axis formation.

Aggregates along the ventral side and directly antagonizes Wnt to inhibit production.

Question 9

Amelia

Answer 9

No limbs are devolved due to no initiation of ZPA

Question 10

Polydactyly

Answer 10

Multiple appendages/phalanges due to improper SHH gradient production.

Question 11

Brachydactyly

Answer 11

Shortened terminal phalanges due to HOXD13 mutation (ineffective)

Question 12

Syndactyly

Answer 12

Webbing of phalanges due to improper BMP production.

Causes no/little apoptosis in mesnechymal between phalanges