Limb Development

Question 1

Limb Initiation

Answer 1

Establishment of the limb fields
dermination of forelimb vs. hindlimb express FGF & Wnts
Acquisition of limb-forming ability and limb budding

Question 2

Proximal Distal Axis

Answer 2

Directs limb outgrowth

Controlled by the apical ectodermal ridge (AER)

Question 3

Anterior posterior Axis

Answer 3

Determines skeletal pattern (position and #)

Controlled by ZPA zone of polarizing activity

Question 4

Dorsal ventral axis

Answer 4

Determines position of tendons and muscles
Determines surface specializations (hair, palm)
Information resides in mesoderm and ectoderm

Question 5

AER

Answer 5

PD control
promotes proliferation and suppresses differentiation of the distal limb mesoderm under it
AER expresses FGFs (FGF4 and FGF8)
perhaps redundancy.

Question 6

Three Proximal Distal segments

Answer 6

Autopod: Hand or foot
Zeugopod: radius/ulna & tibia/ fibia (2 elements)
Stylopod: humerus and femur (1 element)

Question 7

Mechanism of ZPA

Answer 7

ZPA factor is distributed across the limb in a gradient from posterior to anterior with highest [ ] adjacent to the ZPA

Question 8

ZPA signal

Answer 8

shh

Question 9

Shh Signaling

Answer 9

Shh binds to receptor and inhibits Gli3

Gli3 suppresses digit formation

Question 10

Major molecule for DV signaling

Answer 10

Wnt7a