Expression of NvStbm in Nematostella eggs and embryos.(A-E) Whole mount RNA in situ hybridization for NvStbm. (A) Unfertilized egg. (B) Zygote. (C) 8-cell stage. (D) Blastula stage. (E) Gastrula stage. (F-J) NvStbm immunofluorescence in eggs and embryos (red). (F) Unfertilized egg. The female pronucleus at the animal pole (arrow) is labeled with anti-histone antibodies (green). (G) Zygote. (H) 8-cell. (I) Blastula. (J) Gastrula. The blastula and gastrula stages are also stained with phalloidin (green). At the gastrula stage the NvStbm is highly localized to the apical end of cells at the blastopore. The basal ends of these cells are deep inside the blastocoel at this time. (K) Western blot analysis of NvStvbm during early embryogenesis. The anti-NvStbm antiserum recognizes a single band at the expected size of 80 kD. The NvStbm protein is maternally expressed and is expressed at all the examined stages. Anti ß-tubulin was used as a loading control. (L) Preadsoption test of the specificity of the affinity purified anti NvStbm antibodies. Preadsorption of the affinity-purified anti-NvStbm polyclonal antibodies with ten fold molar excess of the NvStbm peptide used as the antigen results in elimination of staining of the 80 kD protein band observed in the control lane incubated with the anti-NvStbm antibodies. Anti ß-tubulin was used as a loading control.