Developmental genetics of Xenopus

Developmental genetics of XenopusbyJessica Burnham LyonsDoctor of Philosophy in Molecular and Cell BiologyUniversity of California, BerkeleyProfessor Richard Harland, ChairThe frog Xenopus laevis has been studied for over 200 years. Its advantages as a robust and easily manipulable model organism have been complemented more recently by genetic and genomic studies in Xenopus tropicalis. My thesis work utilized established and cutting-edge techniques to advance our knowledge of developmental genetics in both Xenopus systems.I used an embryological approach to investigate the roles of the Fgf receptors (Fgfrs) during development. Knockdown and overexpression studies suggested that each Fgfr plays a different role in the specification of mesoderm, and my results are consistent with Fgfr4 playing a role in dampening the Fgf signal. I also showed that X. tropicalis Fgfrs 1-3 are alternatively spliced in D3, the extracellular immunoglobulin domain important for ligand specificity. These isoforms exhibit different temporal and spatial expression patterns, suggesting that control of this alternative splicing plays a role in regulating development.My thesis work has also harnessed the power of the X. tropicalis system to understand development using a forward genetic approach. Tadpoles homozygous for the recessive lethal mutation curly exhibit ventral edema and curled tails. I used classical genetics to map curly to a 1.9 Mb window on X. tropicalis chromosome 4. The pteg gene, which lies in this region, is misspliced in curly embryos. Isabelle Philipp and I used next-generation (nextgen) sequencing technology to identify differences between the curly mutant DNA and that of the reference genome. Focusing on the region around the pteg gene, we are currently evaluating these differences to find the lesion that causes the curly phenotype. The efficient application of genetic techniques requires a high-quality genetic map and reference genome, and those available for X. tr