Genetic Screens for Maternal-Effect Mutations

Publisher Summary This chapter describes approaches and methodologies to carry out genetic screens for maternal-effect mutations. Two approaches have been used to identify de novo recessive maternal-effect mutations in zebrafish: (1) an F4 screen based solely on natural crosses and (2) an F3 screen based on gynogenesis, specifically the technique of Early Pressure. These alternatives differ in various important ways, which are summarized in and described throughout this chapter. Once females are identified as exhibiting a maternal-effect phenotype, the mutation needs to be recovered. The observed maternal-effect phenotypes are expected to be caused by maternal homozygosity for recessive mutations, because dominant mutations are unlikely to be propagated through the generations that occur prior to screening. Because homozygosity for recessive maternal-effect mutations in females leads to the inviability of their progeny, a genetic scheme has to allow the recovery of the mutations through genetically related individuals. Fine mapping a maternal-effect mutation can be performed much more efficiently than the initial mapping. Narrowing down the location of a mutation through fine mapping is necessary to identify the molecular nature of the mutated gene through either candidate gene or positional cloning approaches.