FGF signalling through RAS/MAPK and PI3K pathways regulates cell movement and gene expression in the chicken primitive streak without affecting E-cadherin expression

<p>Abstract</p> <p>Background</p> <p>FGF signalling regulates numerous aspects of early embryo development. During gastrulation in amniotes, epiblast cells undergo an epithelial to mesenchymal transition (EMT) in the primitive streak to form the mesoderm and endoderm. In mice lacking FGFR1, epiblast cells in the primitive streak fail to downregulate E-cadherin and undergo EMT, and cell migration is inhibited. This study investigated how FGF signalling regulates cell movement and gene expression in the primitive streak of chicken embryos.</p> <p>Results</p> <p>We find that pharmacological inhibition of FGFR activity blocks migration of cells through the primitive streak of chicken embryos without apparent alterations in the level or intracellular localization of E-cadherin. E-cadherin protein is localized to the periphery of epiblast, primitive streak and some mesodermal cells. FGFR inhibition leads to downregulation of a large number of regulatory genes in the preingression epiblast adjacent to the primitive streak, the primitive streak and the newly formed mesoderm. This includes members of the FGF, NOTCH, EPH, PDGF, and canonical and non-canonical WNT pathways, negative modulators of these pathways, and a large number of transcriptional regulatory genes. <it>SNAI2 </it>expression in the primitive streak and mesoderm is not altered by FGFR inhibition, but is downregulated only in the preingression epiblast region with no significant effect on E-cadherin. Furthermore, over expression of SNAIL has no discernable effect on E-cadherin protein levels or localization in epiblast, primitive streak or mesodermal cells. FGFR activity modulates distinct downstream pathways including RAS/MAPK and PI3K/AKT. Pharmacological inhibition of MEK or AKT indicate that these downstream effectors control discrete and overlapping groups of genes during gastrulation. FGFR activity regulates components of several pathways known to be required for cell migration through the streak or in the mesoderm, including RHOA, the non-canonical WNT pathway, PDGF signalling and the cell adhesion protein N-cadherin.</p> <p>Conclusions</p> <p>In chicken embryos, FGF signalling regulates cell movement through the primitive streak by mechanisms that appear to be independent of changes in E-cadherin expression or protein localization. The positive and negative effects on large groups of genes by pharmacological inhibition of FGF signalling, including major signalling pathways and transcription factor families, indicates that the FGF pathway is a focal point of regulation during gastrulation in chicken.</p

A Genome-Wide Analysis of FRT-Like Sequences in the Human Genome

Efficient and precise genome manipulations can be achieved by the Flp/FRT system of site-specific DNA recombination. Applications of this system are limited, however, to cases when target sites for Flp recombinase, FRT sites, are pre-introduced into a genome locale of interest. To expand use of the Flp/FRT system in genome engineering, variants of Flp recombinase can be evolved to recognize pre-existing genomic sequences that resemble FRT and thus can serve as recombination sites. To understand the distribution and sequence properties of genomic FRT-like sites, we performed a genome-wide analysis of FRT-like sites in the human genome using the experimentally-derived parameters. Out of 642,151 identified FRT-like sequences, 581,157 sequences were unique and 12,452 sequences had at least one exact duplicate. Duplicated FRT-like sequences are located mostly within LINE1, but also within LTRs of endogenous retroviruses, Alu repeats and other repetitive DNA sequences. The unique FRT-like sequences were classified based on the number of matches to FRT within the first four proximal bases pairs of the Flp binding elements of FRT and the nature of mismatched base pairs in the same region. The data obtained will be useful for the emerging field of genome engineering

Flammer syndrome and autoimmune inflammatory conditions of the central nervous system: multifactorial interrelations

Multiple sclerosis (MS) is the most frequent autoimmune inflammatory and neurodegenerative central nervous system disorder that affects mostly young females and manifests with transient or irreversible neurologic dysfunction caused by demyelination and subsequent axonal transection and neuronal demise. Besides genetic susceptibility, environmental risk factors play a causative role. Although the exact immunopathogenesis has not been fully clarified, the condition is – albeit incurable – amenable to treatment with immunomodulatory drugs. Structural and functional changes in the brain and retinal vasculature in MS causing cerebral hypoperfusion may be a potential pathophysiological link with Flammer Syndrome (FS). However, only one study thus far has systematically investigated the co-occurrence of MS and FS and has shown that multiple symptoms and signs considered as characteristic of FS occur more often in MS patients than in unselected controls. While there is some overlap in symptomatology and clinical findings between the 2 conditions, this does not imply causality, but this preliminary observation should trigger more research on pathophysiological commonalities and clinical course of patients who are eventually diagnosed with both disorders. Susac Syndrome (SuS) is a very rare presumably immune mediated central nervous system disease that affects microvessels in the brain, the retina and the inner ear. This may cause secondary vascular dysregulation and thus signs and symptoms of FS, while it was also proposed that FS may predispose to SuS. However, as in MS assumptions on a potential association of SuS with FS are still poorly supported by rigorous data