<> "The repository administrator has not yet configured an RDF license."^^ . <> . . "Regulatory architecture of the Fgf8 locus and tissue specific control of gene expression"^^ . "During vertebrate development, precise spatio-temporal expression of genes is necessary for growth and tissue differentiation in the embryo. These genes are usually controlled by multiple elements scattered hundreds of kilobases up- and downstream of a target gene, sometimes embedded in introns of functionally non-related genes. This intricate distribution along the chromosome raises the question on the importance of the regulatory architecture for correct gene expression. This is additionally emphasized by several genetic disorders where no mutations in coding regions were found. Instead, it seems they are associated with the disruption of the normal structure of chromosomal domains. Furthermore, distribution of genes and their regulatory elements is mostly conserved across distant species, suggesting they are organized following a specific architecture. To address the role of structural organization of genes and their regulatory elements in achieving proper gene expression, we studied TLX1-FGF8 interval mapped to human chromosome 10q24. This 600kb gene-rich region harbors seven functionally and phylogenetically unrelated genes, representing a “normal” genomic situation. Gene order of the whole region is extremely conserved in tetrapods and to some extent in teleosts and beyond. In addition, human condition split hand-foot malformation type 3 (SHFM3), characterized by the loss of central digits on hand and feet, is caused by 0.5Mb tandem duplication within this locus. FGF8 is coding for a signaling molecule involved in developmental processes, including limb development. Although FGF8 is not within the duplicated interval, the early termination of its expression in the apical ectodermal ridge (AER) contributes to the phenotype. Despite the earlier mapping attempts conducted in mice and fish, full scope of Fgf8 regulatory elements is not determined. Combining mouse transgenesis and chromosomal engineering, I narrowed down the region critical for Fgf8 expression spanning 200kb downstream of the gene. Within it, I characterized individual regulatory elements. Many of them guided the expression of LacZ reporter gene in overlapping domains, suggesting functional redundancy. Also, when tested individually, they express much more regulatory potential than is eventually utilized by Fgf8. Additional experiments using artificial chromosomes (BACs) with inserted LacZ revealed filtering of this potential when elements are in their natural genomic environment. Fine-tuning of regulatory potential can be achieved either by negative elements or the structure of the locus itself. Close proximity of Fgf8 enhancers and promoters of other genes in the region raised the question on how do regulatory elements discriminate between their target and promoters of genes nearby. A series of chromosomal rearrangements reallocating different promoters into Fgf8 regulatory region showed that Fgf8 enhancers are intrinsically capable to activate heterologous promoters and that enhancer-promoter specificity is not exclusively guided by the sequence of the promoter. Rather, the relative position of the two plays a significant role in achieving proper target gene activation. Based on the results of our study, we propose a novel concept of gene regulation: a holo-enhancer. Within a holo-enhancer, vast regulatory potential of multiple enhancers is filtered by their relative position towards the target gene and the activity of potential negative regulators. Also, individual enhancers are able to activate heterologous promoters. However, this intrinsic promiscuity is refined by their position-dependent activity. In a complex genomic environment like the one of Fgf8, gene regulation is not composed of simple binary promoter-enhancer interactions, but is embedded in the structure of the region itself. Once a holo-enhancer is divided into individual elements, their full potential is revealed and perturbations of the region show the potential of enhancers to act on other promoters. This novel concept emphasizes the holistic nature of the interactions of genes and their regulatory elements in achieving gene and tissue specificity, with the overall organization of the locus being a key aspect in this process. These observations led us to suggest the mechanism leading to SHFM3. Duplication breakpoints disrupt the holo-enhancer, reallocating part of the enhancers and releasing them from potential negative elements needed to refine their activities. In addition, a new position brings them to the appropriate distance to heterologous promoters. Their intrinsic promiscuity and broad regulatory potential allows activation of other genes in the region, potentially leading to their up-regulation. Moreover, complex interactions within this region could also explain ancient linkage between functionally unrelated genes (like Fgf8 and Fbxw4), which is most probably due to structural constraints of the regulatory scaffold upon which genes are transcribed."^^ . "2012" . . . . . . . . "Mirna"^^ . "Marinic"^^ . "Mirna Marinic"^^ . . . . . . "Regulatory architecture of the Fgf8 locus and tissue specific control of gene expression (PDF)"^^ . . . "MarinicPhDThesis.pdf"^^ . . . "Regulatory architecture of the Fgf8 locus and tissue specific control of gene expression (Other)"^^ . . . . . . "indexcodes.txt"^^ . . . "Regulatory architecture of the Fgf8 locus and tissue specific control of gene expression (Other)"^^ . . . . . . "lightbox.jpg"^^ . . . "Regulatory architecture of the Fgf8 locus and tissue specific control of gene expression (Other)"^^ . . . . . . "preview.jpg"^^ . . . "Regulatory architecture of the Fgf8 locus and tissue specific control of gene expression (Other)"^^ . . . . . . "medium.jpg"^^ . . . "Regulatory architecture of the Fgf8 locus and tissue specific control of gene expression (Other)"^^ . . . . . . "small.jpg"^^ . . "HTML Summary of #13167 \n\nRegulatory architecture of the Fgf8 locus and tissue specific control of gene expression\n\n" . "text/html" . . . "570 Biowissenschaften, Biologie"@de . "570 Life sciences"@en . .