Screening Of Mutants With Developmental Defects In Zebrafish Generated By ENU Mutagenesis

Functional genomics studies aim to collect information of functions of all genesin the genome. Such information includes not only the structural and biochemicalproperties of the gene products and their roles in specific tissues, but also theloss-of-function phenotypes. Thus, generation of different mutant lines throughmutagenesis is an important approach for studying gene functions.As a good model for studying early development of vertebrates, zebrafish (Daniorerio) gradually attracts general attention. Because of high reproductivity andtransparent embryos, zebrafish becomes the best vertebrate for mutagenesis. In thisstudy, 320 F2 families were established following ENU mutagenesis. Mutants withdefects in epiboly, axis, somite, head, and cardiac and blood systems were identifiedby observing morphological changes in F3 embryos. Additionally, in situhybridization was adopted to identify mutant lines with altered expression patterns ofdpr2, frb35 and insulin.The morphological observation has identified 37 mutant lines, the majority ofwhich showed anomalies in axis and somite formation. Ten of them are kept forfurther study. Screening by in situ hybridization identified a mutant, tipsy, thatshows an abnormal express pattern of dpr2. In some of tipsy mutant embryos, thedorsal midline starts to tilt randomly toward the left or the right during earlygastrulation;subsequently, the body axis skews and the heart is mislocated. Thesephenotypes indicate that the left-right symmetry is interrupted in these tipsy mutantsat early stages of development. It is speculated that the tipsy strain involves two lociand they could be separated by a number of crosses. The mutant lines generated inthis study provide a basis for identification of relevant mutant genes and study ofdevelopmental mechanisms involving these genes.