Gallus gallus
Embryos at HH7/8 each were prepared for roller-tube culture as described in Dupe and Lumsden (2001). Batches of 5 embryos were transferred into sterile 10 ml glass vials containing 2 ml of culture medium (L15 Leibovitz, 10% chicken serum, 0.05 mg/ml gentamicin), supplemented with DMSO (1:1000). The embryos were cultured in a rotary hybridisation oven at 38 degrees Celsius for 6 hours. Thereafter, embryos that had developed normally were collected, and the whole head region up to the 1st somite was harvested in RNALater. For each replicate, total RNA was prepared from 10-15 embryos using the Absolutely RNA Microprep kit (Agilent).