Abstract. ~catenin was identified as a cytoplasmic cadherin-associated protein required for cadherin adhesive function (Nagafuchi, A., and M. Takeichi. 1989.

Analysis of genomic resources available for cnidarians revealed that several key components of the vertebrate innate immune repertoire are present in representatives of the basal cnidarian class Anthozoa, but are missing in Hydra, a member of the class Hydrozoa, indicating ancient origins for many components of the innate immune system.

Abstract. To examine the functions of ERM family members (ezrin, radixin, and moesin), mouse epithelial cells (MTD-1A cells) and thymoma cells (L5178Y), which coexpress all of them, were cultured in the presence of antisense phosphorothioate oligonucleotides (PONs) complementary to ERM sequences. Immunoblotting revealed that the antisense PONs selectively suppressed the expression of each member. Immunofluorescence microscopy of these ezrin, radixin, or moesin "single-suppressed" MTD-1A cells revealed that the ERM family members are colocalized at cell-cell adhesion sites, microvilli, and cleavage furrows, where actin filaments are densely associated with plasma membranes. The ezrin/radixin/moesin antisense PONs mixture induced the destruction of both cell-cell and cell-substrate adhesion, as well as the disappearance of microvilli. Ezrin or radixin antisense PONs individually affected the initial step of the formation of both cell-cell and cell-substrate adhesion, but did not affect the microvilli structures. In sharp contrast, moesin antisense PONs did not singly affect cell-cell and cell-substrate adhesion, whereas it partly affected the microvilli structures. These data indicate that ezrin and radixin can be functionally substituted, that moesin has some synergetic functional interaction with ezrin and radixin, and that these ERM family members are involved in cell-cell and cell-substrate adhesion, as well as microvilli formation.

Abstract. 13-Catenin, a cytoplasmic protein known for its association with cadherin cell adhesion molecules, is also part of a signaling cascade involved in embryonic patterning processes such as the determination of the dorsoventral axis in Xenopus and determination of segment polarity in Drosophila. Previous studies suggest that increased cytoplasmic levels of 13-catenin correlate with signaling, raising questions about the need for interaction with cadherins in this process. We have tested the role of the 13-catenin-cadherin interaction in axis formation. Using [3-catenin deletion mutants, we demonstrate that significant binding to cadherins can be eliminated without affecting the signaling activity. Also, depletion of the soluble, cytosolic pool of 13-catenin by binding to overexpressed C-cadherin completely inhibited [3-catenin-inducing activity. We conclude that binding to cadherins is not required for [3-catenin signaling, and therefore the signaling function of [3-catenin is independent of its role in cell adhesion. Moreover, because 13-catenin signaling is antagonized by binding to cadherins, we suggest that cadherins can act as regulators of the intracellular [3-catenin signaling pathway.

Stem cells are pivotal for development and tissue homeostasis of multicellular animals, and the quest for a gene toolkit associated with the emergence of stem cells in a common ancestor of all metazoans remains a major challenge for evolutionary biology. We reconstructed the conserved gene repertoire of animal stem cells by transcriptomic profiling of totipotent archeocytes in the demosponge Ephydatia fluviatilis and by tracing shared molecular signatures with flatworm and Hydra stem cells. Phylostratigraphy analyses indicated that most of these stem-cell genes predate animal origin, with only few metazoan innovations, notably including several partners of the Piwi machinery known to promote genome stability. The ancestral stem-cell transcriptome is strikingly poor in transcription factors. Instead, it is rich in RNA regulatory actors, including components of the "germ-line multipotency program" and many RNA-binding proteins known as critical regulators of mammalian embryonic stem cells.Porifera | stem cells | evolution | uPriSCs | RNA binding