The lin-12 gene of C. elegans and the Notch gene of D. melanogaster encode structurally related transmembrane proteins that mediate intercellular signaling. We show that truncated forms of these proteins consisting of only the intracellular domains cause cell fate transformations associated with constitutive activity in their respective organisms. This activity does not depend on endogenous gene function. Our results indicate that the intracellular domains of Lin-12 and Notch have intrinsic activity and that the principal role of the extracellular domains in the intact proteins is to regulate this activity. Our results also suggest that equivalent truncated forms of lin-12/Notch family members in vertebrates, including known oncogenes, are similarly active.
"The canonical Notch signaling involves ligand-dependent processing, release, and translocation into the nucleus of the Notch intracellular domain (Nintra/NICD) to activate target genes –. Up-regulation of canonical Notch signaling is associated with the development of the anti-neurogenic phenotype –. The heph embryos manifest the anti-neurogenic phenotype due to increased canonical Notch signaling . "
[Show abstract][Hide abstract] ABSTRACT: The Drosophila polypyrimidine tract-binding protein (dmPTB or hephaestus) plays an important role during embryogenesis. A loss of function mutation, heph03429, results in varied defects in embryonic developmental processes, leading to embryonic lethality. However, the suite of molecular functions that are disrupted in the mutant remains unknown. We have used an unbiased high throughput sequencing approach to identify transcripts that are misregulated in this mutant. Misregulated transcripts show evidence of significantly altered patterns of splicing (exon skipping, 5' and 3' splice site switching), alternative 5' ends, and mRNA level changes (up and down regulation). These findings are independently supported by reverse-transcription-polymerase chain reaction (RT-PCR) analysis and in situ hybridization. We show that a group of genes, such as Zerknüllt, z600 and screw are among the most upregulated in the mutant and have been functionally linked to dorso-ventral patterning and/or dorsal closure processes. Thus, loss of dmPTB function results in specific misregulated transcripts, including those that provide the missing link between the loss of dmPTB function and observed developmental defects in embryogenesis. This study provides the first comprehensive repertoire of genes affected in vivo in the heph mutant in Drosophila and offers insight into the role of dmPTB during embryonic development.
PLoS ONE 07/2014; 9(7):e98585. DOI:10.1371/journal.pone.0098585 · 3.23 Impact Factor
"The same procedure was used for flies expressing GAL4/UAS combinations to knockdown genes using RNAi or to express reporter lines. The following Drosophila stocks were used: Gbe-Su(H)-lacZ (NRE-lacZ) (Furriols and Bray, 2001), Gbe-Su(H)-Gal4 (NRE-Gal4) (Zeng et al., 2010), FRT82B dakt 1 (Rintelen et al., 2001), FRT82B inr 31 (Brogiolo et al., 2001), UAS-dinr RNAi RII2 (a gift from R. Ueda, NIG, Mishima, Japan), UAS-N icd (Struhl et al., 1993), UAS hFOXO3a-TM (Jünger et al., 2003), FRT82B dp110 1C1 [obtained from Hugo Stocker (Willecke et al., 2011)], UAS cut 5 (Krupp et al., 2005), foxo Δ94 and FRT82B foxo Δ94 (Slack et al., 2011), FRT82B inr ex15 (Song et al., 2003) and string-lacZ ( p[w+ stgB R6.4]) (a gift from B. Edgar, ZMBH, Heidelberg). Tub-gal80 ts , UAS-rpr, UAS-dinr del , UAS-cut RNAi TRIP29625, UAS-N RNAi TRIP28981, UAS-p60(PI3K DN ), fizzy related-lacZ and FRT82B strains were from the Bloomington Stock Center. "
[Show abstract][Hide abstract] ABSTRACT: When exposed to nutrient challenge, organisms have to adapt their physiology in order to balance reproduction with adult fitness. In mammals, ovarian follicles enter a massive growth phase during which they become highly dependent on gonadotrophic factors and nutrients. Somatic tissues play a crucial role in integrating these signals, controlling ovarian follicle atresia and eventually leading to the selection of a single follicle for ovulation. We used Drosophila follicles as a model to study the effect of starvation on follicle maturation. Upon starvation, Drosophila vitellogenic follicles adopt an 'atresia-like' behavior, in which some slow down their development whereas others enter degeneration. The mitotic-to-endocycle (M/E) transition is a critical step during Drosophila oogenesis, allowing the entry of egg chambers into vitellogenesis. Here, we describe a specific and transient phase during M/E switching that is paused upon starvation. The Insulin pathway induces the pausing of the M/E switch, blocking the entry of egg chambers into vitellogenesis. Pausing of the M/E switch involves a previously unknown crosstalk between FoxO, Cut and Notch that ensures full reversion of the process and rapid resumption of oogenesis upon refeeding. Our work reveals a novel genetic mechanism controlling the extent of the M/E switch upon starvation, thus integrating metabolic cues with development, growth and reproduction.
"The first, NICD, consists of the intracellular domain only, being truncated just C-terminal to the transmembrane domain. The resulting protein is nuclear and its activity is independent of γ-secretase activity [93–95]. The second, NΔECD, retains the transmembrane region and resembles the product of the Kuz/Adam10 activating cleavage [93,96]. "
[Show abstract][Hide abstract] ABSTRACT: Notch signaling involves a highly conserved pathway that mediates communication between neighboring cells. Activation of Notch by its ligands, results in the release of the Notch intracellular domain (NICD), which enters the nucleus and regulates transcription. This pathway has been implicated in many developmental decisions and diseases (including cancers) over the past decades. The simplicity of the Notch pathway in Drosophila melanogaster, in combination with the availability of powerful genetics, make this an attractive model for studying fundamental principles of Notch regulation and function. In this chapter we present some of the established and emerging tools that are available to monitor and manipulate the Notch pathway in Drosophila and discuss their strengths and weaknesses.
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