text: In situ hybridization.
  Antisense probes were designed to murine epsilony globin nucleotides 509-584; betamaj globin nucleotides 458-549; and mouse Sox6 nucleotides 1353-1927. Embryos were fixed overnight by immersion in 4% paraformaldehyde, embedded in paraffin, sectioned at 5 mum, and adhered to charge modified slides (VWR, West Chester, Pennsylvania, United States). Slides were processed for in situ hybridization as described [52] using in vitro transcribed RNA probes labeled with 33P. Darkfield and brightfield images were obtained with a Nikon Optiphot microscope (Nikon, Melville, New York, United States) and SPOT RT-Slider digital camera (Diagnostic Instruments, Sterling Heights, Michigan, United States). Objectives used were 1x (NA = 0.04) and 10x (NA = 0.5). Images were processed, pseudocolored, and combined using Photoshop (Adobe, San Jose, California, United States) software with Fovea Pro (Reindeer Graphics, Asheville, North Carolina, United States) plugins. Original images are available. 
  