Drosophila Kette coordinates myoblast junction dissolution and the ratio of Scar-to-WASp during myoblast fusion.

The fusion of founder cells and fusion-competent myoblasts (FCMs) is crucial for muscle formation in Drosophila Characteristic events of myoblast fusion include the recognition and adhesion of myoblasts, and the formation of branched F-actin by the Arp2/3 complex at the site of cell-cell contact. At the ultrastructural level, these events are reflected by the appearance of finger-like protrusions and electron-dense plaques that appear prior to fusion. Severe defects in myoblast fusion are caused by the loss of Kette (a homolog of Nap1 and Hem-2, also known as NCKAP1 and NCKAP1L, respectively), a member of the regulatory complex formed by Scar or WAVE proteins (represented by the single protein, Scar, in flies).

Dock mediates Scar- and WASp-dependent actin polymerization through interaction with cell adhesion molecules in founder cells and fusion-competent myoblasts.

The formation of the larval body wall musculature of Drosophila depends on the asymmetric fusion of two myoblast types, founder cells (FCs) and fusion-competent myoblasts (FCMs). Recent studies have established an essential function of Arp2/3-based actin polymerization during myoblast fusion, formation of a dense actin focus at the site of fusion in FCMs, and a thin sheath of actin in FCs and/or growing muscles. The formation of these actin structures depends on recognition and adhesion of myoblasts that is mediated by cell surface receptors of the immunoglobulin superfamily.

The Arf-GEF Schizo/Loner regulates N-cadherin to induce fusion competence of Drosophila myoblasts.

Myoblast fusion is a key process in multinucleated muscle formation. Prior to fusion, myoblasts recognize and adhere to each other with the aid of cell-adhesion proteins integrated into the membrane. Their intracellular domains participate in signal transduction by binding to cytoplasmic proteins.

Three consecutive generations of nephridia occur during development of Platynereis dumerilii (Annelida, Polychaeta).

Molecular data for nephridial development in polychaetes are not available yet. The scope of our work was to establish a reference system for future investigations using two markers for nephridial development: beta-tubulin as marker for cilia and alkaline phosphatase (AP) activity for secretory epithelia. The markers identified, unexpectedly, three consecutively forming generations of nephridia: (1) a transitory unciliated, but AP-positive head kidney, (2) a transitory larval nephridium, which undergoes a morphological transition from a protonephridium to a funnelled nephridium concomitant with the development of the coelomic cavity and finally, (3) the serially arranged metanephridia.

WASP and SCAR have distinct roles in activating the Arp2/3 complex during myoblast fusion.

Myoblast fusion takes place in two steps in mammals and in Drosophila. First, founder cells (FCs) and fusion-competent myoblasts (FCMs) fuse to form a trinucleated precursor, which then recruits further FCMs. This process depends on the formation of the fusion-restricted myogenic-adhesive structure (FuRMAS), which contains filamentous actin (F-actin) plugs at the sites of cell contact.

Blown fuse regulates stretching and outgrowth but not myoblast fusion of the circular visceral muscles in Drosophila.

Circular visceral muscles of Drosophila are binuclear syncytia arising from fusion of two different kinds of myoblasts: a circular visceral founder cell and one visceral fusion-competent myoblast. In contrast to fusion leading to the somatic body-wall musculature, myoblast fusion for the circular visceral muscles does not result in massive syncytia but instead in syncytia interconnected with multiple cytoplasmic bridges, which differentiate into large web-shaped muscles. Here, we show that these syncytial circular visceral muscles build a gut-enclosing network with the interwoven longitudinal visceral muscles.

kette and blown fuse interact genetically during the second fusion step of myogenesis in Drosophila.

Drosophila myoblast fusion proceeds in two steps. The first one gives rise to small syncytia, the muscle precursor cells, which then recruit further fusion competent myoblasts to reach the final muscle size. We have identified Kette as an essential component for myoblast fusion.

Embryonic development of the oligochaete Enchytraeus coronatus: an SEM and histological study of embryogenesis from one-cell stage to hatching.

We describe the embryonic development of the soil-living oligochaete Enchytraeus coronatus (Enchytraeidae, Oligochaeta, Annelida). Enchytraeus coronatus is a direct developer. It follows the typical spiral cleavage mode of development that is highly conserved among annelids and a large number of other lophotrochozoan taxa that are collectively named "Spiralia.