Digoxigenin (DIG)-labeled khdrbs antisense riboprobes were synthesized with linearized vectors (digested by NcoI restriction enzyme) and Sp6 RNA polymerase through in vitro transcription, while synthesis of sense riboprobes used SalI restriction enzyme and T7 RNA polymerase. WISH experimental procedures followed the protocol described by Thisse and Thisse (2008). After staining, the embryos were fixed with 4% paraformaldehyde, rinsed with 70% ethanol and then mounted in glycerin for imaging. The embryos were also washed with PBS, soaked in 30% sucrose (diluted in PBS) overnight and cryosectioned.