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| 2. |
- Gustafsson, Renata, et al.
(author)
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Gene expression profiling of differentiating embryonic stem cells expressing dominant negative fibroblast growth factor receptor 2.
- 2007
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In: Matrix Biology. - : Elsevier BV. - 1569-1802 .- 0945-053X. ; 26, s. 197-205
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Journal article (peer-reviewed)abstract
- Embryonic stein (ES) cells are derived from the inner cell mass of the blastocyst and can be cultured as three-dimensional embryoid bodies (EBs) in which embryonic pregastrulation stages are faithfully mimicked. Fibroblast growth factor receptors (mainly FGFR2) are involved in the first differentiation events during early mammalian embryogenesis. It has been demonstrated that the presence of FGFR2 is a prerequisite for laminin-111 and collagen type IV synthesis and subsequently basement membrane formation in EBs. To identify genes that are influenced by FGFR signalling, we performed global gene expression profiling of differentiating EBs expressing dominant negative FGFR2 (dnFGFR2), acquiring an extensive catalogue of down- and up-regulated genes. We show a strong down-regulation of endodermal and basement membrane related genes, which strengthen the view that the FGFR signalling pathway is a main stimulator of basement membrane synthesis in EBs. We further present down-regulation of genes previously not linked to FGFR signalling, and in addition an active transcription of some mesodermal related genes in differentiating dnFGFR2 EBs.
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| 3. |
- Häger, Mattias, et al.
(author)
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Cib2 binds integrin a7Bb1D and is reduced in laminin a2 chain deficient muscular dystrophy
- 2008
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In: Journal of Biological Chemistry. - 1083-351X. ; 283:36, s. 24760-24769
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Journal article (peer-reviewed)abstract
- Mutations in the gene encoding laminin alpha 2 chain cause congenital muscular dystrophy type 1A. In skeletal muscle, laminin alpha 2 chain binds at least two receptor complexes: the dystrophin-glycoprotein complex and integrin alpha 7 beta 1. To gain insight into the molecular mechanisms underlying this disorder, we performed gene expression profiling of laminin alpha 2 chain-deficient mouse limb muscle. One of the down-regulated genes encodes a protein called Cib2 (calcium-and integrin-binding protein 2) whose expression and function is unknown. However, the closely related Cib1 has been reported to bind integrin alpha IIb and may be involved in outside-in-signaling in platelets. Since Cib2 might be a novel integrin alpha 7 beta 1-binding protein in muscle, we have studied Cib2 expression in the developing and adult mouse. Cib2 mRNA is mainly expressed in the developing central nervous system and in developing and adult skeletal muscle. In skeletal muscle, Cib2 colocalizes with the integrin alpha 7B subunit at the sarcolemma and at the neuromuscular and myotendinous junctions. Finally, we demonstrate that Cib2 is a calcium-binding protein that interacts with integrin alpha 7B beta 1D. Thus, our data suggest a role for Cib2 as a cytoplasmic effector of integrin alpha 7B beta 1D signaling in skeletal muscle.
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| 4. |
- Venugopalan, Shankar R., et al.
(author)
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Novel expression and transcriptional regulation of FoxJ1 during oro-facial morphogenesis
- 2008
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In: Human Molecular Genetics. - : Oxford University Press (OUP). - 0964-6906 .- 1460-2083. ; 17:23, s. 3643-3654
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Journal article (peer-reviewed)abstract
- Axenfeld-Rieger syndrome (ARS) patients with PITX2 point mutations exhibit a wide range of clinical features including mild craniofacial dysmorphism and dental anomalies. Identifying new PITX2 targets and transcriptional mechanisms are important to understand the molecular basis of these anomalies. Chromatin immunoprecipitation assays demonstrate PITX2 binding to the FoxJ1 promoter and PITX2C transgenic mouse fibroblasts and PITX2-transfected cells have increased endogenous FoxJ1 expression. FoxJ1 is expressed at embryonic day 14.5 (E14.5) in early tooth germs, then down-regulated from E15.5-E17.5 and re-expressed in the inner enamel epithelium, oral epithelium, tongue epithelium, sub-mandibular salivary gland and hair follicles during E18.5 and neonate day 1. FoxJ1 and Pitx2 exhibit overlapping expression patterns in the dental and oral epithelium. PITX2 activates the FoxJ1 promoter and, Lef-1 and beta-catenin interact with PITX2 to synergistically regulate the FoxJ1 promoter. FoxJ1 physically interacts with the PITX2 homeodomain to synergistically regulate FoxJ1, providing a positive feedback mechanism for FoxJ1 expression. Furthermore, FoxJ1, PITX2, Lef-1 and beta-catenin act in concert to activate the FoxJ1 promoter. The PITX2 T68P ARS mutant protein physically interacts with FoxJ1; however, it cannot activate the FoxJ1 promoter. These data indicate a mechanism for the activity of the ARS mutant proteins in specific cell types and provides a basis for craniofacial/ tooth anomalies observed in these patients. These data reveal novel transcriptional mechanisms of FoxJ1 and demonstrate a new role of FoxJ1 in oro-facial morphogenesis.
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| 5. |
- Åkerlund, Mikael
(author)
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Gene expression studies of pregastrulation development: the basement membrane is essential for cell differentiation
- 2009
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Doctoral thesis (other academic/artistic)abstract
- Basement membranes (BMs) are sheet-like structures of extracellular matrix. They act as a supporting structure but can also significantly influence cellular behavior in development, tissue homeostasis and disease. Laminins, a major BM component, are multidomain proteins, consisting of three polypeptide chains (α, β and γ). During pregastrulation development, stem cells convert and epithelial tissues are formed. This process is faithfully mimicked in vitro by embryoid body (EB) cultures. Fibroblast growth factor (FGF) signaling is crucial when the step-like process of EB development is initiated with the formation of an endoderm. A subendodermal BM is formed, in which the globular domains LG4-5 of the laminin α1 chain (α1LG4-5) are responsible for the induction of the epiblast EBs derived form embryonic stem (ES) cells, modified to repress FGF receptor signaling, have been described before. However, a full-scale analysis of the transcriptome was missing. We therefore analysed these EBs at four time points during differentiation by the use of microarray technique. An extensive catalogue of affected genes was reported. A majority of the genes directed by FGF signalling were encoding BM and endodermal proteins. In addition, we also analysed the expression profile of wild type EBs. In both these studies, we found interesting genes not previously described in early development or identified as FGF targets. Hopefully, our gene catalogue will be a valuable source for the scientific community interested in FGF signaling, developmental biology and stem cell research. Furthermore, a gene expression study was set up to get a better insight of epiblast inducement by α1LG4-5. EBs derived form ES cells with a targeted deletion of the α1LG4-5 domains were analysed. To our surprise, we found several indications of an incomplete differentiation of the visceral endoderm. We therefore hypothesize a novel autocrine mechanism for α1LG4-5 in regulating the developing endoderm. We also suggest novel roles for laminin LG4-5 in the neuromuscular system. Using laminin α2 chain deficient mice overexpressing laminin α1 chain lacking the LG4-5 domains, we show that these domains, and consequently binding to the receptor dystroglycan are not crucial in diaphragm and heart, but essential in the peripheral nervous system.
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| 6. |
- Åkerlund, Mikael, et al.
(author)
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Laminin alpha1 domains LG4-5 are essential for the complete differentiation of visceral endoderm.
- 2009
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In: Cell and Tissue Research. - : Springer Science and Business Media LLC. - 1432-0878 .- 0302-766X. ; 338:1, s. 129-137
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Journal article (peer-reviewed)abstract
- The heterotrimeric basement membrane protein laminin-111 is essential for early mouse embryogenesis. Its beta1 and gamma1 chains are crucial for endoderm differentiation and for the formation of basement membranes, whereas alpha1 chain null mice only lack the extraembryonic Reichert's membrane. Nevertheless, mice deficient in the cell-binding alpha1 globular domains 4-5 (LG4-5) have a more severe phenotype than animals devoid of the whole alpha1 chain, as these domains are required for the formation of a polarized ectoderm. However, the influence of the alpha1LG4-5 domains on endoderm differentiation is unclear. We have used microarray analysis to compare the expression profiles of normal and alpha1LG4-5-deficient embryoid bodies and show that genes encoding secreted plasma proteins and proteins involved in endocytosis are reduced in alpha1LG4-5-deficient embryoid bodies, indicating incomplete differentiation of the visceral endoderm. Moreover, mice lacking alpha1LG4-5 display endoderm disorganization and a defective expression of the endoderm marker Dab2. We hypothesize that alpha1LG4-5 domains provide an autocrine signal necessary for the complete differentiation of a functional visceral endoderm and vital signals for the polarization of the epiblast.
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