Early mesoderm markers are not affected by Smad1 or Smad5 knockdown. Shown are representative embryos following in situ hybridization for no tail (A-C) or pax2.1 (D-F) at the 5-somite stage in control (A,D), smad1 morphants (B,E), and piggytail mutant embryos (C,F). Pgy/pgy embryos were identified by genotyping after hybridization. Neither Smad1 nor Smad5 loss causes a significant change in the expression pattern of these markers. However, in piggytail embryos, the expression of the hematopoietic marker gata1 is expressed in a compacted pattern that forms a loop bisecting the myod-expressing domain (G,H). A total of 50 embryos per sample were analyzed.