Project description:The hallmark of canonical Wnt signaling is the transcriptional induction of Wnt target genes by the beta-catenin/TCF complex. Several studies have proposed alternative interaction partners for beta-catenin or TCF, but the relevance of potential bifurcations in the distal Wnt pathway remains unclear. Here we study on a genome-wide scale the requirement for Armadillo (Arm, homolog of beta-catenin) and Pangolin (Pan, Drosophila’s TCF) in the Wnt/Wingless (Wg)-induced transcriptional response of Drosophila Kc cells. Using somatic genetics, we demonstrate that both Arm and Pan are absolutely required for mediating activation and repression of target genes. Furthermore, by means of STARR-sequencing we identified Wnt/Wg-responsive enhancer elements and found that all responsive enhancers depend on Pan. Together, our results confirm the dogma of canonical Wnt/Wg signaling and argue against the existence of distal pathway branches in this system.
Project description:The highly conserved Wnt signaling pathway drives intestinal homeostasis across species. Apc is a negative regulator of Wnt signaling. Loss of function mutations in Apc are found in 80-90% of human colorectal cancers. Importantly, Apc loss is widely known as the key driving event in the disease. We used microarray analysis of adult Drosophila midguts to study the molecular mechanisms regulated upon loss of Apc in the intestine.
Project description:It is of tremendous interests to understand how Wnt signaling is regulated in a precise manner both temporally and spatially. Naked cuticle (Nkd) acts as a negative-feedback inhibitor for Wingless (Wg, a fly Wnt) signaling in Drosophila embryonic development. In the present study, we show that nkd is essential for wing pattern formation, such that both gain and loss of nkd result in the disruption of Wg target expression in larvae stage and abnormal adult wing morphologies. Our results of high-throughput sequencing suggest that nkd have profound effects on Drosophila wing development with several critical signaling pathways involved, we conclude that Nkd inhibits the canonical Wg pathway during Drosophila wing development beyond embryonic stage and may play a mediated role in cross-talk between development-related pathways.
Project description:The patterning of Drosophila retina occurs both very fast and with high precision. This process is driven by the dynamic changes in signalling activity of the conserved Hedgehog (Hh) pathway, which coordinates cell fate determination, cell cycle and tissue morphogenesis. Here we show that during Drosophila retinogenesis, the retinal determination gene dachshund (dac) is not only a target of the Hh signaling pathway, but is also a modulator of its activity. Using developmental genetics techniques, we demonstrate that dac enhances Hh signaling by promoting the accumulation of the Gli transcription factor Cubitus interruptus (Ci) parallel to or downstream of fused. In the absence of dac, all Hh-mediated events associated to the morphogenetic furrow are delayed. One of the consequences is that, posterior to the furrow, dac- cells cannot activate a Roadkill-Cullin3 negative feedback loop that attenuates Hh signaling and which is necessary for retinal cells to continue normal differentiation. Therefore, dac is part of an essential positive feedback loop in the Hh pathway, guaranteeing the speed and the accuracy of Drosophila retinogenesis. ChIP-seq against Dachshund vs input ChIP-seq. Eye-antennal imaginal discs are dissected from Grh-GFP (Bloomington stock 42269) 3rd instar larvae and fixed with formaldehyde. Chromatin is prepared and sonicated until fragments reach an average size of 500 bp. Chromatin is immunoprecipitated with an anti-GFP Ab (ab290, Abcam) and the immunocomplexes are recovered with protein A/G magnetic beads (Millipore).
Project description:Following the discovery of BRD4 as a non-oncogene addiction target in acute myeloid leukemia (AML), BET inhibitors are being explored as promising therapeutic avenue in numerous cancers. While clinical trials have reported single-agent activity in advanced hematologic malignancies, mechanisms determining the response to BET inhibition remain poorly understood. To identify factors involved in primary and acquired BET resistance in leukemia, we performed a chromatin-focused shRNAmir screen in a sensitive MLL/AF9; NrasG12D‑driven AML model, and investigated dynamic transcriptional profiles in sensitive and resistant murine and human leukemias. Our screen reveals that suppression of the PRC2 complex, contrary to effects in other contexts, promotes BET resistance in AML. PRC2 suppression does not directly affect the regulation of Brd4-dependent transcripts, but facilitates the remodeling of regulatory pathways that restore the transcription of key targets such as Myc. Similarly, while BET inhibition triggers acute MYC repression in human leukemias regardless of their sensitivity, resistant leukemias are uniformly characterized by their ability to rapidly restore MYC transcription. This process involves the activation and recruitment of WNT signaling components, which compensate for the loss of BRD4 and drive resistance in various cancer models. Dynamic ChIP- and STARR-seq enhancer profiles reveal that BET-resistant states are characterized by remodeled regulatory landscapes, involving the activation of a focal MYC enhancer that recruits WNT machinery in response to BET inhibition. Together, our results identify and validate WNT signaling as a driver and candidate biomarker of primary and acquired BET resistance in leukemia, and implicate the rewiring of transcriptional programs as an important mechanism promoting resistance to BET inhibitors and, potentially, other chromatin-targeted therapies. RNA-Seq of DMSO- or JQ1-treated cancer cell lines; ChIP-seq for H3K36me3 and H3K27me3 in a leukemia cell line treated either with DMSO or JQ1, ChIP-seq for H3K27ac in resistant and sensitive mouse and human leukemia. Functional enhancer mapping (STARR-seq) in K-562 treated either with DMSO or JQ1.