F. Broders et Jp. Thiery, CONTRIBUTION OF CADHERINS TO DIRECTIONAL CELL-MIGRATION AND HISTOGENESIS IN XENOPUS EMBRYOS, Cell adhesion and communication, 3(5), 1995, pp. 419
Perturbation of adhesion mediated by cadherins was achieved by over-ex
pressing truncated forms of E- and EP-cadherins (in which the extracel
lular domain was deleted) in different blastomeres of stage 6 Xenopus
laevis embryos. Injections of mRNA encoding truncated E- and EP-cadher
ins into A1A2 blastomeres resulted in inhibition of cell adhesion and,
at later stages, in morphogenetic defects in the anterior neural tiss
ues to which they mainly contribute. In addition, truncated EP-cadheri
n mRNA produced a duplication of the dorso-posterior axis in a signifi
cant number of cases. The expression of truncated E- and EP-cadherins
in blastomeres involved in gastrulation and neural induction (B1B2 and
C1), led to the duplication of the dorso-posterior axis as well as to
defects in anterior structures. Morphogenetic defects obtained with t
runcated EP-cadherin were more severe than those induced with truncate
d E-cadherin. Cells derived from blastomeres injected with truncated E
P-cadherin mRNA, dispersed more readily at the blastula and gastrula s
tages than the cells derived from the blastomeres expressing truncated
E-cadherin. Presumptive mesodermal cells expressing truncated cadheri
ns did not engage in coherent directional migration. The alteration of
cadherin-mediated cell adhesion led directly to the perturbation of t
he convergent-extension movements during gastrulation as shown in the
animal cap assays and indirectly to perturbation of neural induction.
Although the cytoplasmic domains of type I cadherins share a high degr
ee of Sequence identity, the over-expression of their cytoplasmic doma
ins induces a distinct pattern of perturbations, strongly suggesting t
hat in vivo, each cadherin may transduce a specific adhesive signal. T
hese graded perturbations may in part result from the relative ability
of each cadherin cytoplasmic domain to titer the beta-catenin.