Question

Researchersh ave isolated two E-cadherin mutant isoforms
that are hypothesized ro function differently from the isoform
of the wild-type E-cadherin. An E-cadherin negative mammary
carcinoma cell line was transfected with the mutant
E-cadherin genes A (part a in the figure, triangles) or B (part b)
(triangles)o r the wild-type E-cadhering ene( black circles)a nd
( a ) Anti-E-cadherin
20 40
Time (min)
20 40
Time (min)
80
60
40
80
60
E
540
E20
80
60
80
60
( b )
E
540
E20
844 cHAPTER1 9 | TNTEGRATTNCGE LLStN TO TtSSUES
40
compared to untransfected cells (open circles) in an aggregation
assay. In this assay, cells are first dissociated by trypsin
treatment and then allowed to aggregate in solution over a period
of minutes. Aggregating cells from mutants A and B are
presented in panels a and b respectively. To demonstrate that
the observed adhesion was cadherin mediated, the cells were
pretreated with a nonspecific antibody (left panel) or a functionblocking
anti-E-cadherin monoclonal antibody (right panel)'
a. Vhy do cells transfected with the wild-type Ecadherin
gene have greater aggregation than control, untransfected
cells?
b. From these data, what can be said about the function
of mutants A and B?
c. Sfhy does the addition of the anti-E-cadherin monoclonal
antibodS but not the nonspecific antibody, block
aggregation?
d.
'What
would happen to the aggregation ability of
the cellst ransfectedw ith the wild-type E-c^adherigne nei f the
assay were performed in media low in Ca'-?