Overexpression of Camello, a Member of a Novel Protein Family, Reduces Blastomere Adhesion and Inhibits Gastrulation in Xenopus laevis

Abstract

Vertebrate gastrulation involves complex coordinated movements of cells and cell layers to establish the axial structures and the general body plan. Adhesion molecules and the components of extracellular matrix were shown to be involved in this process. However, other participating molecules and detailed mechanisms of the control of gastrulation movements remain largely unknown. Here, we describe a novel Xenopus gene camello (Xcml) which is expressed in the suprablastoporal zone of gastrulating embryos. Injection of Xcml RNA into dorsovegetal blastomeres retards or inhibits gastrulation movements. Database searches revealed a family of mammalian mRNAs encoding polypeptides highly similar to Xcml protein. Characteristic features of the camello family include the presence of the central hydrophobic domain and the N-acetyltransferase consensus motifs in the C-terminal part, as well as functional similarity to Xcml revealed by overexpression studies in Xenopus embryos. Xcml expression results in the decrease of cell adhesion as demonstrated by the microscopic analysis and the blastomere aggregation assay. Cell fractionation and confocal microscopy data suggest that Xcml protein is localized in the secretory pathway. We propose that Xcml may fine tune the gastrulation movements by modifying the cell surface and possibly extracellular matrix proteins passing through the secretory pathway.