Characterization of the Speed Bump Phenotype in Zebrafish

Abstract

In order for cells to grow and survive they must undergo the cell cycle A large-scale zebrafish mutagenesis produced the speed bump mutant; widely thought to be the result of a mutation in the wee1 gene The kinase Wee1 regulates entry into mitosis by inhibiting the mitosis promoting factor, or MPF If Wee1 can no longer function, the cell can move into mitosis in an earlier phase This study aimed to characterize the speed bump phenotype and to clone wee1 into a heat shock vector, via in vivo homologous recombination, to determine if its expression could rescue the speed bump phenotype back to wild-type The only way to determine if an embryo has been rescued is to characterize and understand the differences between the mutant and wild-type phenotypes Through in situ hybridization, anti-caspase staining, and DAPI staining we were able to determine that wee1 is maternally expressed, and that the zygotic wee1 transcripts, allele ti279, undergo nonsense mediated decay We also found that the earliest cellular defect is at 80% epiboly Surprisingly, we did not find any apoptosis in response to the cellular defects, despite clear embryo deterioration Although we characterized the speed bump mutant, we were unable to confirm that wee1 induces the speed bump phenotype, as we had difficulties cloning the vector Nevertheless, the information we have obtained on wee1 provides key insight into the cell cycle and its processes.