Simple vertebrate models for chemical genetics and drug discovery screens: Lessons from zebrafish and Xenopus

Abstract

Chemical genetics uses small molecules to modulate protein function and, in principle, has the potential to perturb any biochemical event in a complex cellular context. The application of chemical genetics to dissect biological processes has become an attractive alternative to mutagenesis screens due to its technical simplicity, inexpensive reagents, and low-startup costs. In vertebrates, only fish and amphibians are amenable to chemical genetic screens. Xenopus frogs share a long evolutionary history with mammals and so represent an excellent model to predict human biology. In this review, we discuss the lessons learned from chemical genetic studies carried out in zebrafish and Xenopus. We highlight how Xenopus can be employed as a convenient first-line animal model at various stages of the drug discovery and development process and comment on how they represent much-needed tools to bridge the gap between traditional in vitro and preclinical mammalian assays in biomedical research and drug development. Developmental

Optimizing methods for the study of intravascular lipid metabolism in zebrafish

“…At present, organism-based models are widely used in small-chemical compound discovery and such animal-based screening models make compound-screening feasible prior to the elucidation of detailed mechanisms of the signaling pathways involved (16)(17)(18). For an animal-based model, the animal should be small, low-cost, compatible with simple culture conditions and suitable for high-throughput screening (19).…”

Far from solved: A perspective on what we know about early mechanisms of left–right asymmetry

“…One misconception that sometimes appears in the literature is that the data implicating ion flows, gap junctions, and serotonergic signaling derive solely from drugbased inhibition experiments, and thus are subject to all the usual caveats inherent in pharmacological perturbation. Indeed, chemical genetic strategies (Smukste and Stockwell, 2005;Adams and Levin, 2006a,b;Wheeler and Brandli, 2009) are a rapid and inexpensive method for initially implicating targets for further characterization, as well as allowing dissection of the timing of different mechanisms (which is often impossible with genetic manipulations). However, it is crucial to note that the drug screens that first suggested the involvement of physiological early signals and helped narrow their timing of activity were accompanied by experiments using molecular loss-of-function (and sometimes also gain-of-function) gene-specific reagents Levin and Mercola, 1999;Levin et al, 2002;Bunney et al, 2003;Raya et al, 2004;Fukumoto et al, 2005a,b;Adams et al, 2006;Morokuma et al, 2008) in every major study, rendering concerns about pharmacological specificity irrelevant and firmly implicating several ion transport and neurotransmitter pathways in LR patterning.…”

Xenopus: An ideal system for chemical genetics

“…There are many sources for such libraries as discussed in Wheeler and Brandli, 2009. Of course, the choice of the library depends on the researchers' initial goals and will greatly affect the nature of the positive hits.…”

“…However, until recently, chemical genetic screens had not been carried out in Xenopus embryos, and screens using zebrafish have led the way in vertebrates. In recent years, the use of genetics in Xenopus tropicalis (Goda et al, 2006) and work by the authors and others in chemical genetic phenotypic screens have shown Xenopus to be an excellent model system for such screens Longo et al, 2008;Tomlinson et al, 2005Tomlinson et al, , 2009aWheeler and Brandli, 2009). In fact, Xenopus is the only tetrapod vertebrate to have free-living embryos in which embryonic development is neither in utero nor in ovo and thus is the highest order in which highthroughput screens can be carried out (Wheeler and Brandli, 2009).…”

“…The embryos develop in the petridish in simple salt solutions at room temperature. X. laevis embryos are bigger than zebrafish but can still be screened in 96-well plates (Tomlinson et al, 2005(Tomlinson et al, , 2009aWheeler and Brandli, 2009). Compounds can be added to the media, and the vitelline membrane around the embryo is highly porous and accessibility of compounds to the embryo is usually good.…”