Characterization of E-cadherin endocytosis in isolated MCF-7 and Chinese hamster ovary cells - The initial fate of unbound E-cadherin

The endocytosis of E-cadherin has recently emerged as an important determinant of cadherin function with the potential to participate in remodeling adhesive contacts. In this study we focused on the initial fate of E-cadherin when it predominantly exists free on the cell surface prior to adhesive binding or incorporation into junctions. Surface-labeling techniques were used to define the endocytic itinerary of E-cadherin in MCF-7 cells and in Chinese hamster ovary cells stably expressing human E-cadherin. We found that in this experimental system E-cadherin entered a transferrin-negative compartment before transport to the early endosomal compartment, where it merged with classical clathrin-mediated uptake pathways. E-cadherin endocytosis was inhibited by mutant dynamin, but not by an Eps15 mutant that effectively blocked transferrin internalization. Furthermore, sustained signaling by the ARF6 GTPase appeared to trap endocytosed E-cadherin in large peripheral structures. We conclude that in isolated cells unbound E-cadherin on the cell surface is predominantly endocytosed by a clathrin-independent pathway resembling macropinocytotic internalization, which then fuses with the early endosomal system. Taken with earlier reports, this suggests the possibility that multiple pathways exist for E-cadherin entry into cells that are likely to reflect cell context and regulation.

Nervous and muscle system development in Phascolion strombus (Sipuncula)

Recent interpretations of developmental gene expression patterns propose that the last common metazoan ancestor was segmented, although most animal phyla show no obvious signs of segmentation. Developmental studies of non-model system trochozoan taxa may shed light on this hypothesis by assessing possible cryptic segmentation patterns. In this paper, we present the first immunocytochemical data on the ontogeny of the nervous system and the musculature in the sipunculan Phascolion strombus. Myogenesis of the first anlagen of the body wall ring muscles occurs synchronously and not subsequently from anterior to posterior as in segmented spiralian taxa (i.e. annelids). The number of ring muscles remains constant during the initial stages of body axis elongation. In the anterior-posteriorly elongated larva, newly formed ring muscles originate along the entire body axis between existing myocytes, indicating that repeated muscle bands do not form from a posterior growth zone. During neurogenesis, the Phascolion larva expresses a non-metameric, paired, ventral nerve cord that fuses in the mid-body region in the late-stage elongated larva. Contrary to other trochozoans, Phascolion lacks any larval serotonergic structures. However, two to three FMRFamide-positive cells are found in the apical organ. In addition, late larvae show commissure-like neurones interconnecting the two ventral nerve cords, while early juveniles exhibit a third, medially placed FMRFamidergic ventral nerve. Although we did not find any indications for cryptic segmentation, certain neuro-developmental traits in Phascolion resemble the conditions found in polychaetes (including echiurans) and myzostomids and support a close relationship of Sipuncula and Annelida.

The Populist Message of Australian Country Music

Australian country music is influenced by American country music and Australian bush ballads. This music idealises genuine true blue inhabitants of an idealised rural heartland and fuses nationalism with agrarian mythology. The lyrics of a number of country songs contain a populist political message, which is frequently nationalistic but is a form of nationalism.