J. Odenthal

Mutations affecting pigmentation and shape of the adult zebrafish.

Abstract Mutations causing a visible phenotype in the adult serve as valuable visible genetic markers in multicellular genetic model organisms such as Drosophila melanogaster, Caenorhabditis elegans and Arabidopsis thaliana. In a large scale screen for mutations affecting early development of the zebrafish, we identified a number of mutations that are homozygous viable or semiviable. Here we describe viable mutations which produce visible phenotypes in the adult fish. These predominantly affect the fins and pigmentation, but also the eyes and body length of the adult. A number of dominant mutations caused visible phenotypes in the adult fish. Mutations in three genes, long fin, another long fin and wanda affected fin formation in the adult. Four mutations were found to cause a dominant reduction of the overall body length in the adult. The adult pigment pattern was found to be changed by dominant mutations in wanda, asterix, obelix, leopard, salz and pfeffer. Among the recessive mutations producing visible phenotypes in the homozygous adult, a group of mutations that failed to produce melanin was assayed for tyrosinase activity. Mutations in sandy produced embryos that failed to express tyrosinase activity. These are potentially useful for using tyrosinase as a marker for the generation of transgenic lines of zebrafish.

Developmental mutant screens in the zebrafish.

Publisher Summary This chapter focuses on the chemical mutagenesis procedure and screening strategies for efficient induction and recovery of developmental mutations in the zebrafish. The choice of the zebrafish line to be mutagenized depends on the assay and the breeding scheme to be used for the screen. Tu and AB are the two lines that have mainly been used for mutational screens in the past. For specific screens, genetically marked lines such as TL may be more suitable for an efficient screening strategy. For screens requiring the squeezing of females to obtain unfertilized oocytes such as haploid screens or early pressure screens, the AB line seems more suitable because it more readily gives oocytes that can be fertilized in vitro. Whatever line is used, it should be free of lethal and other mutations. Efficient mutagenesis methods and high mutation rates are prerequisites for performing large-scale mutational screens. Several mutagenic reagents, including gamma rays, UV light, and ethylnitrosourea (ENU) have been used to mutagenize zebrafish sperm. In these procedures, sperms are isolated from males, treated with the mutagen, and then used to fertilize eggs in vitro. Alternatively, males have been mutagenized with ENU and immediately mated to females following the mutagenesis.