Fig. 1. slam^waldo mutants have a strong and penetrant germ cell migration phenotype. Anterior is towards the left in all panels. (A,B,D,E) Lateral views. (C,F) Dorsal views. (A-C) Wild-type embryos. (D-F) slam^waldo embryos. All embryos are labeled with -Vasa to mark germ cells in brown. Embryos in A,D are labeled with RACE RNA to mark the midgut in blue. Embryos in B,C,E,F are labeled with the 412 retrotransposon RNA to mark lateral mesoderm and SGPs (arrowheads) in blue. (A,D) By stage 11, germ cells in slam^waldo embryos have properly migrated through the gut epithelium; however, the midgut has not become mesenchymal and flattened out. (B,E) By stage 12, most of the germ cells in wild type (B) are in the mesoderm and in contact with three SGP clusters (arrowheads). Many germ cells in slam^waldo embryos (E) are still on the midgut (arrow), though some are correctly located in the mesoderm next to the two posterior SGP clusters (left two arrowheads in E). (C,F) At stage 14, germ cells and SGPs coalesce to form two round gonads. Though some germ cells in slam^waldo embryos are in the gonads (F), on average 50% are located at ectopic locations, either on the midgut (arrowheads) or in the posterior end of the embryo (arrows).