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- Haecker, Achim, et al.
(författare)
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Drosophila Brakeless interacts with Atrophin and is required for Tailless-mediated transcriptional repression in early embryos
- 2007
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Ingår i: PLoS biology. - : Haecker et al. - 1544-9173 .- 1545-7885. ; 5:6
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Tidskriftsartikel (refereegranskat)abstract
- Complex gene expression patterns in animal development are generated by the interplay of transcriptional activators and repressors at cis-regulatory DNA modules (CRMs). How repressors work is not well understood, but often involves interactions with co-repressors. We isolated mutations in the brakeless gene in a screen for maternal factors affecting segmentation of the Drosophila embryo. Brakeless, also known as Scribbler, or Master of thickveins, is a nuclear protein of unknown function. In brakeless embryos, we noted an expanded expression pattern of the Krüppel (Kr) and knirps (kni) genes. We found that Tailless-mediated repression of kni expression is impaired in brakeless mutants. Tailless and Brakeless bind each other in vitro and interact genetically. Brakeless is recruited to the Kr and kni CRMs, and represses transcription when tethered to DNA. This suggests that Brakeless is a novel co-repressor. Orphan nuclear receptors of the Tailless type also interact with Atrophin co-repressors. We show that both Drosophila and human Brakeless and Atrophin interact in vitro, and propose that they act together as a co-repressor complex in many developmental contexts. We discuss the possibility that human Brakeless homologs may influence the toxicity of polyglutamine-expanded Atrophin-1, which causes the human neurodegenerative disease dentatorubral-pallidoluysian atrophy (DRPLA).
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- Luschnig, Stefan, et al.
(författare)
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Luminal matrices: An inside view on organ morphogenesis
- 2014
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Ingår i: Experimental Cell Research. - : Elsevier BV. - 0014-4827 .- 1090-2422. ; 321:1, s. 64-70
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Tidskriftsartikel (refereegranskat)abstract
- Tubular epithelia come in various shapes and sizes to accommodate the specific needs for transport, excretion and absorption in multicellular organisms. The intestinal tract, glandular organs and conduits for liquids and gases are all lined by a continuous layer of epithelial cells, which form the boundary of the luminal space. Defects in epithelial architecture and lumen dimensions will impair transport and can lead to serious organ malfunctions. Not surprisingly, multiple cellular and molecular mechanisms contribute to the shape of tubular epithelial structures. One intriguing aspect of epithelial organ formation is the highly coordinate behavior of individual cells as they mold the mature lumen. Here, we focus on recent findings, primarily from Drosophila, demonstrating that informative cues can emanate from the developing organ lumen in the form of solid luminal material. The luminal material is produced by the surrounding epithelium and helps to coordinate changes in shape and arrangement of the very same cells, resulting in correct lumen dimensions. © 2013 Elsevier Inc.
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- Mendoza-Garcia, Patricia, 1988-
(författare)
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Harnessing the power of model systems to investigate regulation of Anaplastic Lymphoma Kinase function
- 2019
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The anaplastic lymphoma kinase (ALK), initially identified as a translocation partner in anaplastic large cell lymphoma (ALCL), has been described in a number of tumors such as neuroblastoma. Neuroblastoma is a neural crest derived malignancy of the sympathetic nervous system. Therefore, understanding regulation of ALK transcription and activity in the context of normal neural crest development might highlight abnormal events contributing to neuroblastoma initiation. The use of vertebrate model systems has been very important for studying in detail the pathways activated during neural crest development, their contribution to neuroblastoma and the identification of therapeutic targets.Using a yeast one-hybrid approach, we identified Odd-paired (Opa) as a potential transcription factor modulating Alk expression in the Drosophila visceral mesoderm (VM) (Paper I). Opa promotes Alk expression in the VM in combination with Bagpipe (Bap) and Biniou (Bin) through binding to the here identified AlkEB9 enhancer region.In a subsequent paper, we identified ALKAL1 and ALKAL2 as the activating ligands for the human ALK (Paper II). Using a combination of in vitro and cell culture assays we show that the ALKAL proteins can bind and activate human ALK. Moreover, ALKAL proteins can “super-activate” mutant ALK, highlighting a putative role for the ALKALs/ALK axis in neuroblastoma.The third paper shows in vivo evidence of ALKAL activity during zebrafish neural crest development (Paper III). We identified and characterized three zebrafish Alkal proteins and demonstrated their ability to activate human and zebrafish ALK family RTKs. Zebrafish Alkals activate the ALK-related receptor leukocyte tyrosine kinase (LTK) in the neural crest to promote iridophore development.In the last paper, we employed the DamID approach on the Drosophila VM and identified the transcription factor Kahuli (Kah) as an Alk transcriptional target in this tissue (Paper IV). We also addressed the in vivo iv Kah role during embryogenesis and showed that Kah is required for normal midgut invaginations and formation of the body wall musculature.Together, this thesis highlights the importance of ALK receptor signaling during development in vertebrate and invertebrate models. Further, it shows that ALKAL signaling via the activation of the ALK family receptors are involved in neural crest development.
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- Misra, Tvisha, et al.
(författare)
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A genetically encoded biosensor for visualising hypoxia responses in vivo
- 2017
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Ingår i: Biology Open. - : The Company of Biologists. - 2046-6390. ; 6:2, s. 296-304
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Tidskriftsartikel (refereegranskat)abstract
- Cells experience different oxygen concentrations depending on location, organismal developmental stage, and physiological or pathological conditions. Responses to reduced oxygen levels (hypoxia) rely on the conserved hypoxia-inducible factor 1 (HIF-1). Understanding the developmental and tissue-specific responses to changing oxygen levels has been limited by the lack of adequate tools for monitoring HIF-1 in vivo. To visualise and analyse HIF-1 dynamics in Drosophila, we used a hypoxia biosensor consisting of GFP fused to the oxygen-dependent degradation domain (ODD) of the HIF-1 homologue Sima. GFP-ODD responds to changing oxygen levels and to genetic manipulations of the hypoxia pathway, reflecting oxygen-dependent regulation of HIF-1 at the single-cell level. Ratiometric imaging of GFP-ODD and a red-fluorescent reference protein reveals tissue-specific differences in the cellular hypoxic status at ambient normoxia. Strikingly, cells in the larval brain show distinct hypoxic states that correlate with the distribution and relative densities of respiratory tubes. We present a set of genetic and image analysis tools that enable new approaches to map hypoxic microenvironments, to probe effects of perturbations on hypoxic signalling, and to identify new regulators of the hypoxia response.
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