Fringe‐dependent notch activation and tramtrack function are required for specification of the polar cells in Drosophila oogenesis

Abstract

During Drosophila oogenesis, each egg chamber is encapsulated through the coordinated signaling of multiple pathways, resulting in the formation of polar cells at the termini and a row of stalk cells in between each egg chamber. Notch signaling is required for specification of a precursor group containing both stalk and polar cells. Together, the Notch and JAK/STAT pathways specify the stalk cells as well as a group of prepolar cells, from within that group. The mechanism by which the polar cells differentiate from the prepolar group involves apoptosis, but the pathways which control that process are largely unknown. We now demonstrate that Notch signaling, activated by Delta and transduced by the transcription factor Tramtrack, is involved in the process of refining the prepolar cell group to two polar cells. The glycosyltransferase Fringe is expressed and required cell-autonomously in prepolar cells for this process. However, the transcription factor Mirror, which inhibits fringe expression in other tissues and stages of development, as well as Serrate, one of the two known ligands for Notch, are not required for maturation of prepolar cells. This finding suggests that Fringe is necessary for generating positional information in localizing a high-affinity interaction between Notch and its ligand Delta, even if a second ligand is not essential. Developmental Dynamics 232:1013-1020, 2005.

Drosophilafollicle cells are patterned by multiple levels of Notch signaling and antagonism between the Notch and JAK/STAT pathways

“…2D). Since the polar cell population defined by expression of Fng is initially larger, and is reduced to two cells by programmed cell death (Althauser et al, 2005;Besse and Pret, 2003), this most probably resulted from the presence of wild-type Dl-expressing polar cells that provided the signal prior to their apoptosis. No phenotype was observed when the stalk cells themselves were mutant for Dl (Fig.…”

Notch-dependent downregulation of the homeodomain gene cut is required for the mitotic cycle/endocycle switch and cell differentiation inDrosophilafollicle cells

“…Notably, it is implicated in a lateral inhibition process during neurogenesis that restricts sensoryorgan formation and boundary formation in the wing imaginal disc (Beatus and Lendahl, 1998;Bray, 1998). In oogenesis, Notch signaling has been shown to be implicated in the specification of the polar follicle cells and regulation of cellcycle programs in the follicle-cell epithelium (Althauser et al, 2005;Deng et al, 2001;Grammont and Irvine, 2001;LopezSchier and St Johnston, 2001;Ruohola et al, 1991;Torres et al, 2003).…”

sequoia controls the type I>0 daughter proliferation switch in the developing Drosophila nervous system

“…domain of the Drosophila Tramtrack (Ttk) protein, a member of the BTB-ZF family (Brenman et al, 2001). Both seq and ttk have previously been linked to the Notch pathway (Guo et al, 1996;Brenman et al, 2001;Althauser et al, 2005;Jordan et al, 2006;Andrews et al, 2009). Comparing with mammalian proteins, Seq is most homologous to Prdm10, a member of the positive regulatory domain (PRDM) family, many of which are involved in embryonic development and Notch signaling (Hohenauer and Moore, 2012;Zannino and Sagerstrom, 2015).…”

“…In addition to related zinc fingers, Seq, Ttk and the PRDM family also share an involvement in Notch pathway signaling. ttk has been identified as a Notch pathway target gene and effector, both during oogenesis and ESO development (Guo et al, 1996;Althauser et al, 2005;Jordan et al, 2006). The PRDM family plays important roles during development and is also intimately linked to Notch signaling (Hohenauer and Moore, 2012;Zannino and Sagerstrom, 2015).…”