Figure 3

SGPs are present but fail to attract PGCs in Six4¹³¹homozygous embryos. A, B. Stage 13 wild type (A) and Six4¹³¹homozygous (B) embryos stained for Eya protein. Eya is correctly localised to the nucleus in the mutant SGPs, in contrast to cells lacking Six4 [21, 27]. C. Six4 is required for PGC migration to the SGPs. Six4¹³¹homozygous embryo expressing eGFP-Vasa in PGCs. A small number of PGCs (white arrow) become associated with SGPs in the normal location of the gonad following germ band retraction. The majority remain in ventral and posterior positions at this time. Images are shown at the time points indicated and represent maximum projections of data from 30 deconvolved z sections 1 μm apart. These data are also shown in Additional file 5. D-F. Six4 is required for Hmgcr expression in SGPs. In situ hybridisation using an Hmgcr RNA probe. D. Stage 10 Six4 null embryo. The early, broad expression of Hmgcr in the mesoderm is not dependent on Six4. E. By stage 12 Hmgcr expression is restricted to the SGPs. F. No Hmgcr expression is detected in the SGPs of a Six4¹³¹homozygous embryo.