The Fibroblast Growth Factor Family in the Early Development of Xenopus laevis.

The focus of this thesis has been to investigate the requirement for the function of members of the fibroblast growth factor (FGF) family in early Xenopus development both during mesoderm formation in the blastula and later patterning events in the gastrula and neurula. In particular, much attention is focused on the activities and expression of Xenopus embryonic FGF (eFGF) and how this might relate to the perturbations in development which result from the inhibition of the FGF signal transduction pathway following overexpression of a dominant negative FGF receptor (XFD). A detailed description of the XFD phenotype is presented and shows that inhibition of FGF function leads to a reduction in mesoderm formation and a disruption of its normal pattern. Analysis of gene expression in embryos injected with XFD mRNA demonstrates that FGF activity is required for the correct regulation of a subset of genes within the mesoderm at the start of gastrulation. Prominent amongst these is the Xenopus homologue of the Brachyury gene (Xbra). A detailed in situ hybridisation analysis shows that eFGF is coexpressed with Xbra in the mesoderm of the periblastopore region and notochord during neurula and gastrula stages. Later in development they are both expressed in the developing tailbud. FGF-3 is also expressed in the nascent mesoderm and tailbud but also has complex expression domains in the anterior of the embryo.Experiments in this thesis show that not only is FGF function required for the initial expression of mesodermal genes such as Xbra and XmyoD, but is also required to maintain their expression after the period of mesoderm induction. Furthermore, experiments suggest that eFGF and Xbra are components of an autocatalytic regulatory loop that is important for the development of the mesoderm in vertebrates. These data demonstrate a role for FGF activity both during the induction of mesoderm in the blastula and its maintenance and patterning during gastrula and neurula stages

Two Hundred Years of Sydney Newspapers: A Short History

This booklet was produced to mark the bicentenary of publication of the first Australian newspaper, the Sydney Gazette and New South Wales Advertiser, on 5 March 1803 and to provide a souvenir for those attending the Australian Newspaper Press Bicentenary Symposium at the State Library of New South Wales, Sydney, on 1 March 2003. The Australian Newspaper History Group convened the symposium

Australian newspaper history: a bibliography - additional entries

The bibliography covers national, capital city and provincial newspapers as well as information about media history in Australia since its founding. It also covers ethnic and indigenous press and industrial papers

N1-Src kinase is required for primary neurogenesis in Xenopus tropicalis

The presence of the neuronal-specific N1-Src splice variant of the C-Src tyrosine kinase is conserved through vertebrate evolution, suggesting an important role in complex nervous systems. Alternative splicing involving a N1-Src specific microexon leads to a five or six amino acid insertion into the SH3 domain of Src. A prevailing model suggests that N1-Src regulates neuronal differentiation via cytoskeletal dynamics in the growth cone. Here we have investigated the role of n1-src in the early development of the amphibian Xenopus tropicalis, and find that n1-src expression is regulated in embryogenesis, with highest levels detected during the phases of primary and secondary neurogenesis. In situ hybridisation analysis, using locked nucleic acid (LNA) oligo probes complementary to the n1-src microexon indicate that n1-src expression is highly enriched in the open neural plate during neurula stages and in the neural tissue of adult frogs. Given the n1-src expression pattern, we investigated a possible role for n1-src in neurogenesis. Using splice site-specific antisense morpholino oligos, we are able to inhibit n1-src splicing, whilst preserving c-src expression. Differentiation of neurons in the primary nervous system is reduced in n1-src knockdown embryos, accompanied by a severely impaired touch response in later development. These data reveal an essential role for n1-src in amphibian neural development and suggest that alternative splicing of C-Src in the developing vertebrate nervous system evolved to regulate neurogenesis

N1-Src kinase is required for primary neurogenesis in Xenopus tropicalis

The presence of the neuronal-specific N1-Src splice variant of the C-Src tyrosine kinase is conserved through vertebrate evolution, suggesting an important role in complex nervous systems. Alternative splicing involving a N1-Src specific microexon leads to a five or six amino acid insertion into the SH3 domain of Src. A prevailing model suggests that N1-Src regulates neuronal differentiation via cytoskeletal dynamics in the growth cone. Here we have investigated the role of n1-src in the early development of the amphibian Xenopus tropicalis, and find that n1-src expression is regulated in embryogenesis, with highest levels detected during the phases of primary and secondary neurogenesis. In situ hybridisation analysis, using locked nucleic acid (LNA) oligo probes complementary to the n1-src microexon indicate that n1-src expression is highly enriched in the open neural plate during neurula stages and in the neural tissue of adult frogs. Given the n1-src expression pattern, we investigated a possible role for n1-src in neurogenesis. Using splice site-specific antisense morpholino oligos, we are able to inhibit n1-src splicing, whilst preserving c-src expression. Differentiation of neurons in the primary nervous system is reduced in n1-src knockdown embryos, accompanied by a severely impaired touch response in later development. These data reveal an essential role for n1-src in amphibian neural development and suggest that alternative splicing of C-Src in the developing vertebrate nervous system evolved to regulate neurogenesis

Book Reviews

What does a judge do when he decides a case? It would be interesting to collect the answers ranging from those furnished by primitive systems of law in which the judge was supposed to consult the gods to the ultra-modern, rather profane system described to me recently by a retrospective judge: I make up my mind which way the case ought to be decided, and then I see if I can\u27t get some legal ground to make it stick. Perhaps the widespread impression is the curiously erroneous one lampooned by Gnaeus Flavius (Kantorowitz). The judge is supposed to sit at a green baize tablethe German equivalent in suggestion for our red tape-with nothing before him but a copy of the Biirgerliches Gesetzbucl. Personally, he has no equipment but a perfect thinking machine. The facts are presented to him and a mechanically perfect conclusion is automatically reached. Disregarding entirely the unattainability of this ideal degree of the elimination of the personal equation, one may well ask whether the ideal itself is worth striving to approximate

Attenuation of RNA polymerase II pausing mitigates BRCA1-associated R-loop accumulation and tumorigenesis.

Most BRCA1-associated breast tumours are basal-like yet originate from luminal progenitors. BRCA1 is best known for its functions in double-strand break repair and resolution of DNA replication stress. However, it is unclear whether loss of these ubiquitously important functions fully explains the cell lineage-specific tumorigenesis. In vitro studies implicate BRCA1 in elimination of R-loops, DNA-RNA hybrid structures involved in transcription and genetic instability. Here we show that R-loops accumulate preferentially in breast luminal epithelial cells, not in basal epithelial or stromal cells, of BRCA1 mutation carriers. Furthermore, R-loops are enriched at the 5' end of those genes with promoter-proximal RNA polymerase II (Pol II) pausing. Genetic ablation of Cobra1, which encodes a Pol II-pausing and BRCA1-binding protein, ameliorates R-loop accumulation and reduces tumorigenesis in Brca1-knockout mouse mammary epithelium. Our studies show that Pol II pausing is an important contributor to BRCA1-associated R-loop accumulation and breast cancer development

Regulation of gene expression downstream of a novel Fgf/Erk pathway during Xenopus development

Activation of Map kinase/Erk signalling downstream of fibroblast growth factor (Fgf) tyrosine kinase receptors regulates gene expression required for mesoderm induction and patterning of the anteroposterior axis during Xenopus development. We have proposed that a subset of Fgf target genes are activated in the embyo in response to inhibition of a transcriptional repressor. Here we investigate the hypothesis that Cic (Capicua), which was originally identified as a transcriptional repressor negatively regulated by receptor tyrosine kinase/Erk signalling in Drosophila, is involved in regulating Fgf target gene expression in Xenopus. We characterise Xenopus Cic and show that it is widely expressed in the embryo. Fgf overexpression or ectodermal wounding, both of which potently activate Erk, reduce Cic protein levels in embryonic cells. In keeping with our hypothesis, we show that Cic knockdown and Fgf overexpression have overlapping effects on embryo development and gene expression. Transcriptomic analysis identifies a cohort of genes that are up-regulated by Fgf overexpression and Cic knockdown. We investigate two of these genes as putative targets of the proposed Fgf/Erk/Cic axis: fos and rasl11b, which encode a leucine zipper transcription factor and a ras family GTPase, respectively. We identify Cic consensus binding sites in a highly conserved region of intron 1 in the fos gene and Cic sites in the upstream regions of several other Fgf/Cic co-regulated genes, including rasl11b. We show that expression of fos and rasl11b is blocked in the early mesoderm when Fgf and Erk signalling is inhibited. In addition, we show that fos and rasl11b expression is associated with the Fgf independent activation of Erk at the site of ectodermal wounding. Our data support a role for a Fgf/Erk/Cic axis in regulating a subset of Fgf target genes during gastrulation and is suggestive that Erk signalling is involved in regulating Cic target genes at the site of ectodermal wounding