A hormone-dependent post-translationally regulated mutant for investigating type I cadherin function.

Type I cadherins are Ca2+-dependent cell adhesion molecules. Their function in early Xenopus laevis development has been extensively studied in recent years, by injecting synthetic mRNAs encoding dominant negative mutants with deletions of the extracellular domain into embryos. However, studies at post-gastrula stages have been hampered by the inabilityto progress through post-gastrula development in embryos expressing these mutant proteins. This problem has been partly overcome by injecting into a few targeted blastomeres in stage 6 N.F. embryos, but only restricted studies are possible with this technique. Several studies have made use of the hormone-binding domain (HBD), which is activated by hormones. In this study, we used this method to analyze the activity of dominant negative cadherins. We generated a mutant E-cadherin (AE-Cad, consisting of the cytoplasmic domain and transmembrane domain) fused to the hormone-binding domain of estradiol receptor (HBDER) and we validated this technique with functional analyses. The function of the mutant deltaE-HBDER was strictly dependent on hormone induction. This conditional mutant had the same effects and exerted the same dominant negative function as the corresponding constitutive mutant.