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Zebrafish as a vertebrate model to study retinoic acid signalling in head mesoderm and pectoral fin development and to investigate non-ion channel epilepsies

Zebrafish as a vertebrate model to study retinoic acid signalling in head mesoderm and pectoral fin development and to investigate non-ion channel epilepsies

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GIBERT, Yann, 2004. Zebrafish as a vertebrate model to study retinoic acid signalling in head mesoderm and pectoral fin development and to investigate non-ion channel epilepsies [Dissertation]. Konstanz: University of Konstanz

@phdthesis{Gibert2004Zebra-7813, title={Zebrafish as a vertebrate model to study retinoic acid signalling in head mesoderm and pectoral fin development and to investigate non-ion channel epilepsies}, year={2004}, author={Gibert, Yann}, address={Konstanz}, school={Universität Konstanz} }

deposit-license application/pdf Zebrafisch als Wirbeltiermodellsystem zur Untersuchung des Retinsäuresignalwegs in der Entwicklung des Kopfmesoderms und der Brustflossen, so wie von Nicht-Ionenkanalepilepsien Gibert, Yann 2011-03-24T17:37:44Z Gibert, Yann eng Retinoic acid (RA) is a key signal involved in the posteriorization of vertebrate neural ectoderm. The major enzyme involved in biosynthesis of RA during embryonic development is retinaldehyde dehydrogenase 2 (Raldh2). A zebrafish mutant in raldh2 (neckless; nls), which is devoid of RA signalling during embryonic development, exhibits anterior-posterior (AP) patterning defects in the neural ectoderm. Using the nls mutant I found that loss of RA also affects AP patterning of the cranial mesoderm. I depleted RA signalling in embryos and found that markers of the posterior cranial mesoderm are shortened along the AP axis, correlating with the severity of RA depletion. I determined the timing for requirement of RA to establish the AP-level of the posterior border of head mesoderm. Together with the pattern of raldh2 expression, I conclude that during gastrulation, RA biosynthesis in prospective mesoderm is a key signal for the specification of the AP extent of the posterior cranial mesoderm. RA-antagonist experiments further reveal that AP-patterning processes are coordinated between the neural tube and the paraxial mesoderm, aligning the hindbrain-spinal cord and head-trunk mesoderm boundaries.<br />Vertebrate forelimbs arise as bilateral appendages from the lateral plate mesoderm (LPM). nls mutants have been used to show that initiation of limb development and patterning of the limb bud are crucially dependent on RA signaling. However, the timing and cellular origin of RA signaling in these processes have remained poorly resolved. We have used genetics and chemical modulators of RA signaling to solve these issues in the zebrafish. By rescuing pectoral fin induction in the aldh1a2/neckless mutant with exogenous RA and by blocking RA signaling in wild type embryos, we find that RA acts as a permissive signal that is required during the 6-8 somite stages for pectoral fin induction. Cell-transplantation experiments show that RA production is not only critically required from flanking somites, but is sufficient for fin bud initiation when the trunk mesoderm is genetically ablated. Under the latter condition, intermediate mesoderm alone cannot induce the pectoral fin field in the LPM. We further show that induction of the fin field is directly followed by a continued requirement for somite-derived RA signaling to establish a prepattern of antero-posterior fates in the condensing fin mesenchyme. This process is mediated by the maintained expression of the transcription factor hand2, through which the fin field is continuously posteriorized. Thus RA signaling from flanking somites plays a dual early role in the condensing limb bud mesenchyme.<br />Mutations in leucine-rich glioma-inactivated 1 (LGI1) have been shown to cause an idiopathic epilepsy syndrome, ADLTE. Using expression data of lgi genes in zebrafish and molecular evolutionary analysis among a complete set of nucleotide sequences of the vertebrate LGI sub-groups, I showed that all vertebrate LGI1 and LGI4 genes appear to be under strong purifying selection, the other groups show a pattern of more relaxed selection. Thus, statistical evolutionary tests using the PAML software, in conjunction with expression analyses, can be utilized to determine evolutionary constraints within gene families and help to explain the etiology of ADLTE.<br />LGI genes share a conserved domain with the Very Large G-protein coupled Receptor-1 (VLGR1/Mass1/USH2C) gene, which is mutated in a murine model of epilepsy. Mutations in VLGR1 are associated with audiogenic epilepsy in mice and Usher syndrome (sensorineural deafness and retinitis pigmentosa) in humans. I characterized the zebrafish VLGR1 gene (vlgr1). It is 51% identical to human VLGR1 in amino acid sequence, but is 64% identical in the 7-transmembrane and cytoplasmic domains. It is 6199 amino acids in size and is encoded by a 19.2 kb mRNA. All introns correspond in location and phase to those of the human and mouse genes. In situ hybridization studies of zebrafish embryos demonstrate high level vlgr1 expression in the developing CNS, particularly in the diencephalon, surrounding the third, tectal and fourth ventricles, and associated with the optic nerve. Further studies using zebrafish may help ascertain the role of Vlgr1 in neural development. 2004 2011-03-24T17:37:44Z Zebrafish as a vertebrate model to study retinoic acid signalling in head mesoderm and pectoral fin development and to investigate non-ion channel epilepsies

Dateiabrufe seit 01.10.2014 (Informationen über die Zugriffsstatistik)

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