Question

You work in a developmental biology lab that uses Xenopus laevis (the African clawed frog) as a model organism. You are working on a project investigating the activity of different cadherins in cells. You insert a transgene to express RFP-E-cadherin (red) in neural crest cells from Xenopus embryos and GFP-N-Cadherin in a second set of neural crest cells from Xenopus embryos. These cells do not normally express ANY cadherins. Explain the results you expect to see in the following cultures. a. Culture A: cells that express RFP-E-cadherin b. Culture B: A mixture of cells expression RFP-E-cadherin and GFP-N-Cadherin-expressing cells c. Culture C: cells that express RFP-E-cadherin which have been transfected with an siRNA to knock-down the gene that codes for fibronectin d. Culture D: Cells that express GFP-N-cadherin grown in the presence of EGTA, a compound that depletes free Ca2+ concentration from the culture medium

Answer 1

A. The cells express RFP-E-cadherin appears red in color.
B. A mixture of cells expression RFP-E-cadherin and GFP-N-Cadherin-expressing cells express both Red and green inside the cells.
C. siRNA to knock-down the gene that codes for fibronectin leads to N-cadherin was concentrated along areas of
cell-cell contact in confluent monolayers devoid of fibronectin. So, N-cadherin Red stain localizes to cell-cell
contacts at cell borders.
D. Calcium chelator (EGTA) to disrupt the adhesive interaction, cells not contact with each other. Green fluroscence express inside the cells.