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Dan Weeks, PhD
Professor of Biochemistry and PediatricsCarver College of MedicineUniversity of Iowa51 Newton Rd, 4-710 BSBIowa City, IA 52242
Phone: (319) 335-7918Lab Phone: (319) 335-7919Fax: (319) email@example.com
Figure 1. Whole mount confocal analysis showing innervation (green) of a tadpole ear. Images taken by S.J. Kolker.
The selective inactivation of gene expression is one of the most powerful ways to understand the cellular function of a particular gene product. This approach has been most successfully adopted in mutagenic analysis of organisms ranging from viruses and bacteria to yeast, nematodes, fruit flies and more recently mice. However, as the size and the expense of the organism increases, full mutational analysis becomes less feasible. In fact, for most organisms, it would be difficult to justify the expense and effort required to simulate the genetic approach used in organisms like yeast, fruit flies, zebra fish or mice.
One method to selectively inactivate gene expression in "genetically challenging" organisms is the introduction of oligonucleotides into the cell. There are several ways that oligonucleotides might be used for this purpose. The most commonly used method is to design oligonucleotides that hybridize with specific mRNA molecules leading to degradation of mRNA and loss of de novo protein synthesis.
When the transcription factor PitX2c is reduced using cationic
antisense oligonucleotide, the developing heart fails to fully execute
it's normal asymmetry program. (from Dagle et al. 2003)
We are developing and using chemically modified cationic oligonucleotides that enhance the ability of the oligo to act as an antisense agent. We have also shown that these modified oligos can be used to form sequence specific triple helices in vitro under ionic conditions that approximate those found in the nucleus. These promising modifications will be tested for toxicity and efficacy while examining their affect on genes expressed during embryogenesis in the frog Xenopus laevis.
We use the cationic oligos and other techniques to examine genes implicated in congenital heart and ear defects. We investigate spatial and temporal expression of genes involved in the development of these two organ systems as well as the early embryonic effects of having mutations that in humans lead to congenital defects. These studies will provide new approaches for the study of gene expression and function in Xenopus laevis, as well as providing a rapid, vertebrate based method for examining gene function.
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