18 wheeler regulates apical constriction of salivary gland cells via the Rho-GTPase-signaling pathway.

Rho GTPase and its upstream activator, guanine nucleotide exchange factor 2 (RhoGEF2), have emerged as key regulators of actin rearrangements during epithelial folding and invagination (Nikolaidou, K.K., Barrett, K.

Different Wnt signals act through the Frizzled and RYK receptors during Drosophila salivary gland migration.

Guided cell migration is necessary for the proper function and development of many tissues, one of which is the Drosophila embryonic salivary gland. Here we show that two distinct Wnt signaling pathways regulate salivary gland migration. Early in migration, the salivary gland responds to a WNT4-Frizzled signal for proper positioning within the embryo.

Two ligands signal through the Drosophila PDGF/VEGF receptor to ensure proper salivary gland positioning.

The Drosophila embryonic salivary gland is a migrating tissue that undergoes a stereotypic pattern of migration into the embryo. We demonstrate that the migratory path of the salivary gland requires the PDGF/VEGF pathway. The PDGF/VEGF receptor, Pvr, is strongly expressed in the salivary glands, and Pvr mutations cause abnormal ventral curving of the glands, suggesting that Pvr is involved in gland migration.

Tec29 controls actin remodeling and endoreplication during invagination of the Drosophila embryonic salivary glands.

Epithelial invagination is necessary for formation of many tubular organs, one of which is the Drosophila embryonic salivary gland. We show that actin reorganization and control of endocycle entry are crucial for normal invagination of the salivary placodes. Embryos mutant for Tec29, the Drosophila Tec family tyrosine kinase, showed delayed invagination of the salivary placodes.

Src64 is involved in fusome development and karyosome formation during Drosophila oogenesis.

Src family tyrosine kinases respond to a variety of signals by regulating the organization of the actin cytoskeleton. Here, we show that during early oogenesis Src64 mutations lead to uneven accumulation of cortical actin, defects in fusome formation, mislocalization of septins, defective transport of Orb protein into the oocyte, and possible defects in cell division. Similar mutant phenotypes suggest that Src64, the Tec29 tyrosine kinase, and the actin crosslinking protein Kelch act together to regulate actin crosslinking, much as they do later during ring canal growth.

NETRIN and SLIT guide salivary gland migration.

Directed migration is pivotal for the proper placement and function of nearly all organs. The majority of known guidance molecules involved in directed migration have been identified from studies of migrating axons during nervous system development. Here, we show that at least two of these axon guidance molecules, NETRIN and SLIT, act through their canonical receptors, to guide Drosophila embryonic salivary glands.

senseless is necessary for the survival of embryonic salivary glands in Drosophila.

Apoptosis in developing Drosophila embryos is rare and confined to specific groups of cells. We explain how one organ, salivary glands, of Drosophila embryos avoids apoptosis. senseless (sens), a Zn-finger transcription factor, is expressed in the salivary primordium and later in the differentiated salivary glands.

Two Pax genes, eye gone and eyeless, act cooperatively in promoting Drosophila eye development.

We report the identification of a Drosophila Pax gene, eye gone (eyg), which is required for eye development. Loss-of-function eyg mutations cause reduction or absence of the eye. Similar to the Pax6 eyeless (ey) gene, ectopic expression of eyg induces extra eye formation, but at sites different from those induced by ey.

The COP9 signalosome promotes degradation of Cyclin E during early Drosophila oogenesis.

The COP9 signalosome (CSN) is an eight-subunit complex that regulates multiple signaling and cell cycle pathways. Here we link the CSN to the degradation of Cyclin E, which promotes the G1-S transition in the cell cycle and then is rapidly degraded by the ubiquitin-proteasome pathway. Using CSN4 and CSN5/Jab1 mutants, we show that the CSN acts during Drosophila oogenesis to remove Nedd8 from Cullin1, a subunit of the SCF ubiquitin ligase.

CSN5/Jab1 mutations affect axis formation in the Drosophila oocyte by activating a meiotic checkpoint.

The COP9 signalosome (CSN) is linked to signaling pathways and ubiquitin-dependent protein degradation in yeast, plant and mammalian cells, but its roles in Drosophila development are just beginning to be understood. We show that during oogenesis CSN5/JAB1, one subunit of the CSN, is required for meiotic progression and for establishment of both the AP and DV axes of the Drosophila oocyte. The EGFR ligand Gurken is essential for both axes, and our results show that CSN5 mutations block the accumulation of Gurken protein in the oocyte.