Laura Faas

Bio: Laura Faas is an academic researcher from University of York. The author has contributed to research in topics: Xenopus & Population. The author has an hindex of 10, co-authored 16 publications receiving 293 citations.

Valorisation strategies for cocoa pod husk and its fractions

Abstract: Cocoa pod husk (CPH) is the main by-product (ca. 70–75% weight of whole fruit) of the cocoa harvest, an important and economic crop in developing countries. It is a rich source of minerals (particularly potassium), fibre (including lignin, cellulose, hemicellulose and pectin) and antioxidants (e.g. phenolic acids). An existing practise is the return of CPH to soil with potential benefits (or disadvantages) for cocoa productivity and soil sustainability that have not been fully characterised. Currently, alternative low-value applications of CPH include its use as animal feed, as a starting material for soap making and activated carbon. Other biotechnological valorisation potentials for CPH and its fractions include the production of bio-fuels and their incorporation in food systems. Physical, chemical or biological pre-treatment approaches are needed in order to achieve desirable fractions in a cost-effective and sustainable manner for novel applications in food and non-food sectors.

Overlapping functions of Cdx1, Cdx2, and Cdx4 in the development of the amphibian Xenopus tropicalis

Abstract: Using Xenopus tropicalis, we present the first analysis of the developmental effects that result from knocking down the function of the three Cdx genes present in the typical vertebrate genome. Knockdowns of individual Cdx genes lead to a similar range of posterior defects; compound Cdx knockdowns result in increasingly severe posterior truncations, accompanied by posterior shifts and reduction of 5′ Hox gene expression. We provide evidence that Cdx and Wnt3A genes are components of a positive feedback loop operating in the posterior axis. We show that Cdx function is required during later, but not early stages of development, for correct regional specification of the endoderm and morphogenesis of the gut. Our results support the hypothesis that during amphibian development the overall landscape of Cdx activity in the embryo is more important than the specific function of individual Cdx proteins. Developmental Dynamics 238:835–852, 2009. © 2009 Wiley-Liss, Inc.

Characterisation of the fibroblast growth factor dependent transcriptome in early development.

Abstract: Background FGF signaling has multiple roles in regulating processes in animal development, including the specification and patterning of the mesoderm. In addition, FGF signaling supports self renewal of human embryonic stem cells and is required for differentiation of murine embryonic stem cells into a number of lineages. Methodology/Principal Findings Given the importance of FGF signaling in regulating development and stem cell behaviour, we aimed to identify the transcriptional targets of FGF signalling during early development in the vertebrate model Xenopus laevis. We analysed the effects on gene expression in embryos in which FGF signaling was inhibited by dominant negative FGF receptors. 67 genes positively regulated by FGF signaling and 16 genes negatively regulated by FGF signaling were identified. FGF target genes are expressed in distinct waves during the late blastula to early gastrula phase. Many of these genes are expressed in the early mesoderm and dorsal ectoderm. A widespread requirement for FGF in regulating genes expressed in the Spemann organizer is revealed. The FGF targets MKP1 and DUSP5 are shown to be negative regulators of FGF signaling in early Xenopus tissues. FoxD3 and Lin28, which are involved in regulating pluripotency in ES cells are shown to be down regulated when FGF signaling is blocked. Conclusions We have undertaken a detailed analysis of FGF target genes which has generated a robust, well validated data set. We have found a widespread role for FGF signaling in regulating the expression of genes mediating the function of the Spemann organizer. In addition, we have found that the FGF targets MKP1 and DUSP5 are likely to contribute to the complex feedback loops involved in modulating responses to FGF signaling. We also find a link between FGF signaling and the expression of known regulators of pluripotency.

Lin28 proteins are required for germ layer specification in Xenopus

Abstract: Lin28 family proteins share a unique structure, with both zinc knuckle and cold shock RNA-binding domains, and were originally identified as regulators of developmental timing in Caenorhabditis elegans. They have since been implicated as regulators of pluripotency in mammalian stem cells in culture. Using Xenopus tropicalis, we have undertaken the first analysis of the effects on the early development of a vertebrate embryo resulting from global inhibition of the Lin28 family. The Xenopus genome contains two Lin28-related genes, lin28a and lin28b. lin28a is expressed zygotically, whereas lin28b is expressed both zygotically and maternally. Both lin28a and lin28b are expressed in pluripotent cells of the Xenopus embryo and are enriched in cells that respond to mesoderm-inducing signals. The development of axial and paraxial mesoderm is severely abnormal in lin28 knockdown (morphant) embryos. In culture, the ability of pluripotent cells from the embryo to respond to the FGF and activin/nodal-like mesoderm-inducing pathways is compromised following inhibition of lin28 function. Furthermore, there are complex effects on the temporal regulation of, and the responses to, mesoderm-inducing signals in lin28 morphant embryos. We provide evidence that Xenopus lin28 proteins play a key role in choreographing the responses of pluripotent cells in the early embryo to the signals that regulate germ layer specification, and that this early function is probably independent of the recognised role of Lin28 proteins in negatively regulating let-7 miRNA biogenesis.

Conserved and novel roles for the Gsh2 transcription factor in primary neurogenesis.

Abstract: The Gsx genes encode members of the ParaHox family of homeodomain transcription factors, which are expressed in the developing central nervous system in members of all major groups of bilaterians. The Gsx genes in Xenopus show similar patterns of expression to their mammalian homologues during late development. However, they are also expressed from early neurula stages in an intermediate region of the open neural plate where primary interneurons form. The Gsx homologue in the protostome Drosophila is expressed in a corresponding intermediate region of the embryonic neuroectoderm, and is essential for the correct specification of the neuroblasts that arise from it, suggesting that Gsx genes may have played a role in intermediate neural specification in the last common bilaterian ancestor. Here, we show that manipulation of Gsx function disrupts the differentiation of primary interneurons. We demonstrate that, despite their similar expression patterns, the uni-directional system of interactions between homeodomain transcription factors from the Msx, Nkx and Gsx families in the Drosophila neuroectoderm is not conserved between their homologues in the Xenopus open neural plate. Finally, we report the identification of Dbx1 as a direct target of Gsh2-mediated transcriptional repression, and show that a series of cross-repressive interactions, reminiscent of those that exist in the amniote neural tube, act between Gsx, Dbx and Nkx transcription factors to pattern the medial aspect of the central nervous system at open neural plate stages in Xenopus.

The regulation of TGFβ signal transduction

Abstract: Transforming growth factor beta (TGFbeta) pathways are implicated in metazoan development, adult homeostasis and disease. TGFbeta ligands signal via receptor serine/threonine kinases that phosphorylate, and activate, intracellular Smad effectors as well as other signaling proteins. Oligomeric Smad complexes associate with chromatin and regulate transcription, defining the biological response of a cell to TGFbeta family members. Signaling is modulated by negative-feedback regulation via inhibitory Smads. We review here the mechanisms of TGFbeta signal transduction in metazoans and emphasize events crucial for embryonic development.

FGF signalling: diverse roles during early vertebrate embryogenesis

Abstract: Fibroblast growth factor (FGF) signalling has been implicated during several phases of early embryogenesis, including the patterning of the embryonic axes, the induction and/or maintenance of several cell lineages and the coordination of morphogenetic movements. Here, we summarise our current understanding of the regulation and roles of FGF signalling during early vertebrate development.