Abstract
ABSTRACTDevelopment 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.
Highlights
Receptor tyrosine kinase (RTK) signaling enables transduction of extracellular signals into the cell and is essential in a wide range of developmental processes
We used transgenic Drosophila expressing DNA adenine methyltransferase (Dam) methylase fused to RNA-Pol II (Southall et al, 2013), driven either generally in the mesoderm or in the visceral mesoderm (VM), resulting in methylation at GATC sites in targeted tissue (Fig. 1A; Movies 1-4)
To manipulate Anaplastic Lymphoma Kinase (Alk) signaling we used combinatorial expression of either UAS-Jelly Belly (Jeb), which leads to ectopic activation of Alk, or UASAlk.EC.MYC, encoding a MYC-tagged extracellular domain (ECD) of Alk that inhibits Alk signaling in a dominant-negative manner (Bazigou et al, 2007) (Fig. 1A,C-E)
Summary
Receptor tyrosine kinase (RTK) signaling enables transduction of extracellular signals into the cell and is essential in a wide range of developmental processes. Ligand-dependent RTK activation is conserved among metazoans, leading to engagement of signal transduction adaptor proteins, serine/threonine kinases and transcription factors (TFs) that regulate gene expression and promote a wide range of intracellular responses. Handling Editor: Thomas Lecuit Received January 2021; Accepted October 2021 ligand Jelly Belly (Jeb), are involved in the development of the visceral mesoderm (VM), where they drive a signaling pathway required for specification of muscle founder cells (FCs) (Englund et al, 2003; Lee et al, 2003; Stute et al, 2004). The influence of Alk signaling on later events in visceral myogenesis is unclear; Alk activity is required for visceral decapentaplegic (dpp) expression in the VM (Shirinian et al, 2007)
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