All Courses

Gradient formation of Fgf8 is governed by both diffusion from a localized source and removal of Fgf8 ligand through endocytosis. Both Rab5C and dynam

Question

Gradient formation of Fgf8 is governed by both diffusion from a localized source and removal of Fgf8 ligand through endocytosis. Both Rab5C and dynamin promote endocytosis. What would happen to the Fgf8 concentration gradient when Rab5C is overexpressed or dynamin is inhibited?

A

Solution

Sol.

Rab5C overexpression enhances endocytosis, increasing removal of Fgf8 from the extracellular space, leading to a steeper and lower concentration gradient.
Dynamin inhibition blocks endocytosis, reducing Fgf8 removal, resulting in a flatter and higher concentration gradient.
Graph C correctly shows the steeper gradient for Rab5C overexpression and flatter gradient for dynamin inhibition compared to normal.

Fgf8 is a morphogen whose gradient is tightly regulated by synthesis, diffusion, and clearance (endocytosis).
Rab5C is a small GTPase promoting endocytosis, enhancing ligand internalization and degradation.
Dynamin is essential for vesicle scission during endocytosis; inhibiting dynamin decreases ligand uptake, causing accumulation.
This regulation ensures precise spatial signaling during development.

Match the terms used in vertebrate limb development in List I with their descriptions in List II:

List I	List II
A. EMT	I. The cells found within the most posterior region of the limb bud
B. Mesenchyme	II. The thickening of ectoderm at the apex of the developing limb
C. AER	III. A loosely organized, mainly mesodermal embryonic tissue
D. Progress zone	IV. Epithelial cells making up the mesoderm of the early somatopleure undergo this transition and get included in mesenchyme cell pool
E. ZPA	V. The proliferative mesenchyme that fuels limb bud growth
F. Autopod	VI. The distal part of tetrapod limb