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Genome-wide identification of Grainy head target genes and their functions in Drosophila embryos
Stockholm University, Faculty of Science, Department of Molecular Biosciences, The Wenner-Gren Institute. (Christos Samakovlis)
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The transcription factor Grainy head (Grh) is conserved from Drosophila to humans. Drosophila Grh plays important roles in epithelial differentiation and regeneration. To investigate the mechanisms of Grh function, we performed ChIP-sequencing and microarray gene expression analysis and identified Grh target genes in Drosophila embryos at a genome-wide scale. We found Grh ChIP peaks in the proximity of 3754 genes and showed that Grh acts both as an activator and as a repressor. 

Grh regulates distinct genes in different contexts. During wound healing, Grh transcriptionally activates stitcher (stit), a gene encoding a receptor tyrosine kinase. We show that Stit activates two distinct pathways, including Src kinases and extracellular signal-regulated kinase (ERK), after injury. The tyrosine residue Y762 mediates Stit binding to the SH2 domains of Src42A, Src64B, or Drk. Src family kinases and Drk act as downstream effectors of Stit in the activation of wound response enhancers. Src family kinases control re-epithelialization, but fail to induce the dpERK accumulation after injury. In contrast, Drk is dispensable in re-epithelialization, but can induce the activation of ERK, which can therefore link RTKs to ERK-mediated Grh-dependent activation of wound response genes. In airways, Grh regulates 1152 target genes encoding various enzymes, signaling proteins, and transcription factors. Grh represses the POU-domain transcription factor Vvl (Ventral veinless). Vvl interacts with Grh and can regulate a set of Grh target genes. Grh and Vvl antagonize each other during airway maturation and tracheal tube elongation. The analysis of Grh-responsive enhancers during embryonic development and in wound healing indicates that Grh cooperates with other transcription factors, such as Vvl, to regulate target gene expression.

In addition, we identify a novel grh PO isoform expressed predominantly in the central nervous system, epidermis, and trachea. Unlike the canonical grh (grh PI) that can regulate endogenous grh PI and grh PO, Grh PO fails to regulate the grh gene transcriptionally. Further functional analysis in the trachea suggests that Grh PO may act as a partial dominant-negative regulator of Grh.

Place, publisher, year, edition, pages
Stockholm: Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University , 2016. , 64 p.
Keyword [en]
Grainy head, Stitcher, Vvl, wound healing, Tracheal development, Drosophila
National Category
Developmental Biology
Research subject
Developmental Biology
Identifiers
URN: urn:nbn:se:su:diva-129571OAI: oai:DiVA.org:su-129571DiVA: diva2:923236
Public defence
2016-06-14, De Geersalen, Geovetenskapens hus, Svante Arrhenius väg 14, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: Manuscript. Paper 3: Manuscript.

Available from: 2016-05-20 Created: 2016-04-26 Last updated: 2016-05-12Bibliographically approved
List of papers
1. Src kinases and ERK activate distinct responses to Stitcher receptor tyrosine kinase signaling during wound healing in Drosophila
Open this publication in new window or tab >>Src kinases and ERK activate distinct responses to Stitcher receptor tyrosine kinase signaling during wound healing in Drosophila
2014 (English)In: Journal of Cell Science, ISSN 0021-9533, E-ISSN 1477-9137, Vol. 127, no 8, 1829-1839 p.Article in journal (Refereed) Published
Abstract [en]

Metazoans have evolved efficient mechanisms for epidermal repair and survival following injury. Several cellular responses and key signaling molecules that are involved in wound healing have been identified in Drosophila, but the coordination of cytoskeletal rearrangements and the activation of gene expression during barrier repair are poorly understood. The Ret-like receptor tyrosine kinase (RTK) Stitcher (Stit, also known as Cad96Ca) regulates both re-epithelialization and transcriptional activation by Grainy head (Grh) to induce restoration of the extracellular barrier. Here, we describe the immediate downstream effectors of Stit signaling in vivo. Drk (Downstream of receptor kinase) and Src family tyrosine kinases bind to the same docking site in the Stit intracellular domain. Drk is required for the full activation of transcriptional responses but is dispensable for re-epithelialization. By contrast, Src family kinases (SFKs) control both the assembly of a contractile actin ring at the wound periphery and Grh-dependent activation of barrier-repair genes. Our analysis identifies distinct pathways mediating injury responses and reveals an RTK-dependent activation mode for Src kinases and their central functions during epidermal wound healing in vivo.

Keyword
Drk, Drosophila, ERK, Src-family kinases, Stitcher, RTK signaling, Wound healing
National Category
Cell Biology
Research subject
Developmental Biology
Identifiers
urn:nbn:se:su:diva-104154 (URN)10.1242/jcs.143016 (DOI)000334595500018 ()
Note

AuthorCount:3;

Available from: 2014-06-09 Created: 2014-06-03 Last updated: 2016-05-11Bibliographically approved
2. Genome-wide identification of Grainy head target genes in Drosophila reveals complex regulatory interactions between Grh and the POU-domain transcription factor, Vvl
Open this publication in new window or tab >>Genome-wide identification of Grainy head target genes in Drosophila reveals complex regulatory interactions between Grh and the POU-domain transcription factor, Vvl
Show others...
(English)Manuscript (preprint) (Other academic)
National Category
Developmental Biology
Research subject
Developmental Biology
Identifiers
urn:nbn:se:su:diva-129397 (URN)
Available from: 2016-04-21 Created: 2016-04-21 Last updated: 2016-05-11Bibliographically approved
3. A new grh isoform in Drosophila and functional analysis of Grh domains in Drosophila
Open this publication in new window or tab >>A new grh isoform in Drosophila and functional analysis of Grh domains in Drosophila
(English)Manuscript (preprint) (Other academic)
National Category
Developmental Biology
Research subject
Developmental Biology
Identifiers
urn:nbn:se:su:diva-129398 (URN)
Available from: 2016-04-21 Created: 2016-04-21 Last updated: 2016-05-11Bibliographically approved

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Yao, Liqun
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