Expression of Cyclin B1 and Cyclin B2 in Specter Zebrafish Mutant

Abstract

Understanding the cell cycle and the genes involved is crucial for understanding how organisms grow and develop. Zebrafish (Danio rerio) were chosen for this study. Previous research has identified several genetic mutations for early development, including specter. Specter has been shown to be a mutation in the cyclin B1 gene through knockout but not through recuse with the wild-type allele. There are two strains: tu21 (null) and ro1. spr tu21 is a recessive loss of function mutation in cyclin B1 whereas the ro1 allele is a gain of function mutation where the mutant embryos produce an altered form of zygotic cyclin B1 mRNA, which produces a Cyclin B1 protein that prevents cell divisions. Previous studies have hypothesized that cyclin B2 may even compensate for cyclin B1 function when it is not functioning properly; cyclin B2 may potentially form a cyclin B2/Cdk1 complex which would allow mitosis to progress. To further characterize cyclin B1 and cyclin B2 in the specter mutant for both strains of tu21 and ro1, in situ hybridizations were done. We showed that cyclin B1 and cyclin B2 are maternally and zygotically expressed in embryos progressing through mitosis and that it is possible that cyclin B2 may be compensating for a malfunctioning cyclin B1. To test cyclin B1 as a candidate gene for specter, other than by knockout, we aimed to incorporate a functional copy of wild-type cyclin B1 into the specter genome to rescue the specter phenotype to wild type. Although this study was unable to determine if phenotypic rescue of specter was successful, it establishes cyclin B1 is viable for homologous recombination which can elucidate the complexity of the cell cycle mechanisms for early vertebrate development as well as contribute to the area of cancer study.