The characterization of novel fibroblast growth factor response genes in Xenopus laevis

Winsor, Wendy (1999) The characterization of novel fibroblast growth factor response genes in Xenopus laevis. Masters thesis, Memorial University of Newfoundland.

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Abstract

In a search for fibroblast growth factor (FGF)-regulated early response genes, four cDNA fragments were isolated via a polymerase chain reaction-based differential display procedure. The cDNA fragments represent portions of genes that were either activated or repressed in Stage 8 Xenopus laevis explants after a 30 minute treatment with lOOng/ml XFGF-2. One 498bp cDNA fragment, named Band V, represents a gene that is downregulated by FGF treatment. This gene is expressed at Stages 8, 9 and 15 in the developing Xenopus embryo. A Genbank homology search program revealed similarity of Band V to distinct regions in an alternatively spliced myocyte enhancer factor, the v-j- c region of a T-cell receptor gamma chain, a Meprin A beta-subunit precursor and a myosin I heavy chain-like protein. The three other cDNA bands isolated from the differential display were chosen due to apparent upregulation by FGF. The 449bp Band VIA/B cDNA fragment possesses regions of similarity to the reactive centre of murine serine proteinase inhibitor 2.4 and a contrapsin-related MC-7 precursor. Upregulation of Band VIA/B was not confirmed because gene expression could not be detected via PCR in Xenopus explants or throughout development. The third Band 11/12, is a 636bp cDNA fragment whose gene is only expressed at Stage 8 of the developing embryo and was upregulated by FGF-2, in a PCR reaction. A database homology search showed that Band 11/12 was similar to a hypothetical protein. A second, 190bp DNA fragment isolated from Band 12 was a portion of the c-mos protooncogene. The fourth and final cDNA Band 22 is 517bp in size and represents a previously cloned Xenopus 146kDa nuclear splicing factor (Schmidt-Zachmann et aL, 1998). This factor is expressed throughout Xenopus development, and control of Band 22 gene expression by FGF-2 could not be confirmed.

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