Building and specializing epithelial tubular organs: the Drosophila salivary gland as a model system for revealing how epithelial organs are specified, form and specialize

Self Cite

Transcription factors affect spatiotemporal patterns of gene expression often regulating multiple aspects of tissue morphogenesis, including cell-type specification, cell proliferation, cell death, cell polarity, cell shape, cell arrangement and cell migration. In this work, we describe a distinct role for Ribbon (Rib) in controlling cell shape/volume increases during elongation of the Drosophila salivary gland (SG). Notably, the morphogenetic changes in rib mutants occurred without effects on general SG cell attributes such as specification, proliferation and apoptosis. Moreover, the changes in cell shape/volume in rib mutants occurred without compromising epithelial-specific morphological attributes such as apicobasal polarity and junctional integrity. To identify the genes regulated by Rib, we performed ChIP-seq analysis in embryos driving expression of GFP-tagged Rib specifically in the SGs. To learn if the Rib binding sites identified in the ChIP-seq analysis were linked to changes in gene expression, we performed microarray analysis comparing RNA samples from age-matched wild-type and rib null embryos. From the superposed ChIP-seq and microarray gene expression data, we identified 60 genomic sites bound by Rib likely to regulate SG-specific gene expression. We confirmed several of the identified Rib targets by qRT-pCR and/or in situ hybridization. Our results indicate that Rib regulates cell growth and tissue shape in the Drosophila salivary gland via a diverse array of targets through both transcriptional activation and repression. Furthermore, our results suggest that autoregulation of rib expression may be a key component of the SG morphogenetic gene network.

Section: Introductionmentioning

confidence: 99%

“…In addition, cell polarity is maintained throughout the duration of tube formation, elongation and migration. For these reasons, the Drosophila salivary gland is an attractive system to study organogenesis and, in particular, to track morphogenesis (Chung et al, 2014; Girdler and Roper, 2014). …”

Section: Introductionmentioning

confidence: 99%

Ribbon regulates morphogenesis of the Drosophila embryonic salivary gland through transcriptional activation and repression

Loganathan

Lee

Wells

et al. 2016

Self Cite

“…Correct final positioning of the embryonic SG requires input from multiple surrounding tissues (Chung et al, 2014). Integrin signaling is essential for posterior migration of the SG along the VM (Bradley et al, 2003).…”

Section: Discussionmentioning

confidence: 99%

“…Tissue-specific transcription factors trigger signaling cascades and downstream effectors that induce cell differentiation and organ specialization (Chung et al, 2014; Cleveland et al, 2012; Loganathan et al, 2016; Rankin and Zorn, 2014; Zaret, 2016). A critical part of this process is ensuring that organ-specific products are synthesized at the right levels at the right time and that organs acquire their final correct size, shape and position in the developing animal.…”

Section: Introductionmentioning

confidence: 99%

Drosophila FoxL1 non-autonomously coordinates organ placement during embryonic development

Hanlon

Andrew

2016

Self Cite

Determining how organs attain precise positioning within an organism is a crucial facet of developmental biology. The Fox family winged-helix transcription factors are known to play key roles in development of multiple organs. Drosophila FoxL1 (aka Fd64A) is dynamically expressed in embryos but its function is completely uncharacterized. FoxL1 is expressed in a single group of body wall - muscles in the 2nd and 3rd thoracic segments, in homologous abdominal muscles at earlier stages, and in the hindgut mesoderm from early through late embryogenesis. We show that FoxL1 expression in T2 and T3 is in VIS5, which is not a single muscle spanning the entire thorax, as previously published, but is, instead, three individual muscles, each spanning a single thoracic segment. We generate mutations in foxL1 and show that, surprisingly, none of the tissues that express FoxL1 are affected by its loss. Instead, loss of foxL1 results in defects in salivary gland positioning and morphology, as well as defects in the migration of hemocytes, germ cells and Malpighian tubules. We also show that FoxL1-dependent expression of secreted Sema2a in T3 VIS5 is required for normal salivary gland positioning. Altogether, these findings suggest that Drosophila FoxL1 functions like its mammalian counterpart in non-autonomously orchestrating the behaviors of surrounding tissues.

“…In particular, the Drosophila embryonic salivary gland is an excellent system for studying how cells migrate collectively as an intact tubular structure. The salivary glands consist of a pair of elongated secretory tubes that are connected to the larval mouth by the duct tubes (Chung et al, 2014; Maruyama and Andrew, 2012; Pirraglia and Myat, 2010). After salivary gland cells invaginate from the ventral surface of the embryo, the tube is initially oriented dorsally.…”

Section: Introductionmentioning

confidence: 99%

Drosophila KASH-domain protein Klarsicht regulates microtubule stability and integrin receptor localization during collective cell migration

Myat

Rashmi

Manna

et al. 2015

During collective migration of the Drosophila embryonic salivary gland, cells rearrange to form a tube of a distinct shape and size. Here, we report a novel role for the Drosophila KASH (Klarsicht-Anc-Syne Homology) domain protein Klarsicht (Klar) in the regulation of microtubule (MT) stability and integrin receptor localization during salivary gland migration. In wild-type salivary glands, MTs became progressively stabilized as gland migration progressed. In embryos specifically lacking the KASH domain containing isoforms of Klar, salivary gland cells failed to rearrange and migrate, and these defects were accompanied by decreased MT stability and altered integrin receptor localization. In muscles and photoreceptors, KASH isoforms of Klar work together with Klaroid (Koi), a SUN domain protein, to position nuclei; however, loss of Koi had no effect on salivary gland migration, suggesting that Klar controls gland migration through novel interactors. The disrupted cell rearrangement and integrin localization observed in klar mutants could be mimicked by overexpressing Spastin (Spas), a MT severing protein, in otherwise wild-type salivary glands. In turn, promoting MT stability by reducing spas gene dosage in klar mutant embryos rescued the integrin localization, cell rearrangement and gland migration defects. Klar genetically interacts with the Rho1 small GTPase in salivary gland migration and is required for the subcellular localization of Rho1. We also show that Klar binds tubulin directly in vitro. Our studies provide the first evidence that a KASH-domain protein regulates the MT cytoskeleton and integrin localization during collective cell migration.