DamID transcriptional profiling identifies the Snail/Scratch transcription factor Kahuli as an Alk target in the Drosophila visceral mesoderm
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ABSTRACT: We used targeted DamID (TaDa) to identify Alk targets in embryos overexpressing Jeb versus embryos with abrogated Alk activity, revealing differentially expressed genes, including the Snail/Scratch family transcription factor Kahuli (Kah)
Project description:DamID transcriptional profiling identifies the Snail/Scratch transcription factor Kahuli as an Alk target in the Drosophila visceral mesoderm
Project description:Numerous roles for the Alk receptor tyrosine kinase have been described in Drosophila, including functions in the CNS, however the molecular details are poorly understood. To gain mechanistic insight, we employed Targeted DamID (TaDa) transcriptional profiling to identify targets of Alk signaling in the larval CNS. TaDa was employed in larval CNS tissues, while genetically manipulating Alk signaling output. The resulting TaDa data were analysed together with larval CNS scRNA-seq datasets performed under similar conditions, identifying a role for Alk in the transcriptional regulation of neuroendocrine gene expression. Further integration with bulk/scRNA-seq and protein datasets from larval brains in which Alk signaling was manipulated, identified a previously uncharacterized Drosophila neuropeptide precursor encoded by CG4577 as an Alk signaling transcriptional target. CG4577, which we named Sparkly (Spar), is expressed in a subset of Alk-positive neuroendocrine cells in the developing larval CNS, including circadian clock neurons. In agreement with our TaDa analysis, overexpression of the Drosophila Alk ligand Jeb resulted in increased levels of Spar protein in the larval CNS. We show that Spar protein is expressed in circadian (Clock) neurons, and Spar mutants exhibit defects in sleep and circadian rhythm control. In summary, we report a novel activity regulating neuropeptide precursor gene that is regulated by Alk signaling in the Drosophila CNS.
Project description:Development of the Drosophila visceral muscle depends on Anaplastic Lymphoma Kinase (Alk) receptor tyrosine kinase (RTK) signaling, which specifies founder cells (FCs) in the circular visceral mesoderm (VM). Although Alk activation by its ligand Jelly Belly (Jeb) is well characterized, few target molecules have been identified. Here, we used targeted DamID (TaDa) to identify Alk targets in embryos overexpressing Jeb versus embryos with abrogated Alk activity, revealing differentially expressed genes, including the Snail/Scratch family transcription factor Kahuli (Kah). We confirmed Kah mRNA and protein expression in the VM, and identified midgut constriction defects in Kah mutants similar to those of pointed (pnt). ChIP and RNA-Seq data analysis defined a Kah target-binding site similar to that of Snail, and identified a set of common target genes putatively regulated by Kah and Pnt during midgut constriction. Taken together, we report a rich dataset of Alk-responsive loci in the embryonic VM and functionally characterize the role of Kah in the regulation of embryonic midgut morphogenesis.
Project description:Histone modifications play a key role in regulating gene expression and cell fate during development and disease. Current methods for cell-type specific genome-wide profiling of histone modifications require dissociation and isolation of cells and are not compatible with all tissue types. Here we adapt Targeted DamID to recognise specific histone marks, by fusing chromatin binding proteins or single-chain antibodies to Dam, an E. coli DNA adenine methylase. When combined with Targeted DamID (TaDa), this enables cell-type specific chromatin profiling in intact tissues or organisms. We first profiled H3K4me3, H3K9ac, H3K27me3 and H4K20me1 in vivo in neural stem cells of the developing Drosophila brain. Next, we mapped cell-type specific H3K4me3, H3K9ac and H4K20me1 distributions in the developing mouse brain. Finally, we injected RNA encoding DamID constructs into 1-cell stage Xenopus embryos to profile H3K4me3 distribution during gastrulation and neurulation. These results illustrate the versatility of Targeted DamID to profile cell-type specific histone marks throughout the genome in diverse model systems.
Project description:This project’s aim was to compare the transcriptional profiles of olfactory sensory neurons in Drosophila melanogaster in order to identify novel genes that specify neuron-specific functions/phenotypes or may otherwise be involved in the development of the olfactory system. The isolation of sufficient numbers of intact olfactory sensory neurons (OSN) from the antenna of Drosophila melanogaster has so far limited single-cell transcriptomic approaches being applied to the adult fly antenna. Targeted DamID (TaDa) provides an alternative approach for profiling transcriptional activity in a cell-specific manor that bypasses the need for isolating OSN. Using the Gal4/UAS system, we applied TaDa to seven OSN populations and compared differences in Pol II occupancy for genes across these datasets.
Project description:kdm5 is an essential gene in Drosophila that has critical developmental roles in the prothoracic gland cells of the larval ring gland. To profile KDM5 binding within these cells and this developmental stage, we performed Targeted DamID (TaDa). By profiling the nearest genes to significant TaDa peaks (FDR < 0.01), we identified 5815 candidate KDM5 target genes. Interestingly, 42% of these candidate KDM5 target genes appear to be conserved across multiple cellular contexts in Drosophila and span many cellular processes for future investigation.
Project description:In this study we adapt targeted DamID (TaDa) for use in C.elegans and employ it to identify targets within the epidermis for the transcription factors LIN-22 and NHR-25 that are key epidermal development regulators.
Project description:Sequencing studies of autism spectrum disorder (ASD) cases have revealed a causal role for mutations to chromatin remodeling genes. Chromodomain helicase DNA binding protein 8 (CHD8) encodes a chromatin remodeler with one of the highest de novo mutation rates in sporadic ASD. However, the relationship between CHD8 genomic function and autism-relevant biology remains poorly elucidated. CHD8 binding studies have relied on Chromatin Immunoprecipitation followed by sequencing (ChIP-seq), but these datasets exhibit significant variation. ChIP-seq has technical limitations in the context of weak or indirect protein-DNA interactions or when high-performance antibodies are unavailable. Thus, complementary approaches are needed to establish CHD8 genomic targets. Here we used Targeted DamID in utero to characterize CHD8 binding activity in the developing embryonic mouse cortex. CHD8 Targeted DamID followed by sequencing (CHD8 TaDa-seq) revealed binding at previously identified genomic targets as well as at genes sensitive to Chd8 haploinsufficiency. CHD8 TaDa-seq showed greater sensitivity for CHD8 binding near a subset of genes specific to brain development and neuron function. These studies establish TaDa-seq as a useful alternative for mapping protein-DNA interactions in vivo and provide insights into the relationship between chromatin remodeling by CHD8 and autism-relevant pathophysiology associated with CHD8 mutations.
Project description:The precise control of gene expression by transcription factor networks is critical to organismal development. The predominant approach for mapping transcription factor-chromatin interactions has been chromatin immunoprecipitation (ChIP). However, ChIP requires a large number of homogeneous cells and antisera with high specificity. A second approach, DamID, has the drawback that high levels of Dam methylase are toxic. Here we modify our Targeted DamID approach (TaDa) to enable cell type-specific expression in mammalian systems, generating an inducible system (mammalian TaDa or MaTaDa) to identify protein/DNA interactions in 100 to 1000 times fewer cells than ChIP. We mapped the binding sites of key pluripotency factors, OCT4 and PRDM14, in mouse embryonic stem cells, epiblast-like cells and primordial germ cell-like cells (PGCLCs). PGCLCs are an important system to elucidate primordial germ cell development in mice. We monitored PRDM14 binding during the specification of PGCLCs, identifying direct targets of PRDM14 that are key to understanding its critical role in PGCLC development. We show that MaTaDa is a sensitive and accurate method to assess cell type specific transcription factor binding in limited numbers of cells.
Project description:Transcriptional profiling of mouse 4T1 breast cancer cells stably tranduced with pLEX-MCS based lentivirus. Three groups were compared, Vector cells, SNAIL expressing cells; and SNAIL+FBXO11 expressing cells. SNAIL expression induced strong EMT phenotype while SNAIL/FBXO11 reversed cells back to epithelial cells.