Lect. 25 - Limb Devpt I

Question 1

Result of experiment removing half of the limb

Answer 1

Remaining half will form a complete limb

Question 2

Role of Tbx5 in initiation of limb development

Answer 2

Initiates future forelimb

Question 3

Role of Tbx4 and Pitx-1 in limb development

Answer 3

Initiates future hindlimb

Question 4

What are the initial initiators of limb development?

Answer 4

Tbx4 and Tbx5

Question 5

Role of Gli3 and Hand2 in initiation of limb development

Answer 5

Gli3 (anterior) and Hand2 (posterior) fix AP axis

Question 6

Role of FGF-10 in initiation of limb development

Answer 6

Mesoderm to ectoderm

Question 7

Role of FGF-8 in initiation of limb development

Answer 7

Ectoderm to mesoderm

Question 8

What are the 3 axes that define the vertebrate limb?

Answer 8

Dorsoventral; anterior-posterior axis; and proximodistal axis

Question 9

Hox8

Answer 9

Determine position of ZPA via its highest concentration; expression is induced by RA

Question 10

Shh

Answer 10

Signal produced by ZPA; also maintains structure and function of AER; induces expression of gremlin

Question 11

Gremlin

Answer 11

Inhibits BMP-2 which inhibits FGF-4 in AER and inhibits Gli-3 in posterior part of limb bud

Question 12

Gli-3

Answer 12

In anterior part of limb bud; inhibits expression of shh in anterior part of limb bud

Question 13

Interactions of AER and limb bud mesoderm

Answer 13

Interacts w/ underlying limb bud mesoderm and promotes continued outgrowth of limb bud

Question 14

Role of Hox genes in limb patterning

Answer 14

Pattern formation in the proximodistal limb axis

Question 15

Relationship of Msx expression to the distal mesenchyme

Answer 15

Cells in the distal limb bud express Msx-1

Question 16

What factors makes up the outgrowth-promoting signal?

Answer 16

FGFs (8, 4, 9, 17) and Wnts

Question 17

What is the role of apoptosis in limb development?

Answer 17

It’s a mechanism for morphogenesis; posterior necrotic zone (will become the axilla) and areas b/w future digits

Question 18

Results of experiment dividing the disc into two halves and physically separating the 2 halves

Answer 18

Each half will form a normal limb