Fig. 1. Generation of the Eph mutant. (A) The P114 P element lies 3 kb upstream of the Eph transcription start site and 300 bp upstream of the onecut transcription start site. Below are shown the extents of three deletions generated using P114. Eph^x652 removes the first three exons of Eph, including the transcription and translation start sites; it also removes 5' sequences from the onecut transcription unit, but does not remove the onecut translation initiation site. Also shown are two deletions extending solely in the direction of the onecut transcription unit, onecut^lx122 and onecut^lx49. Both break within the onecut-coding region. (B) In situ hybridization of Eph antisense RNA to a stage 15 wild-type embryo. Eph expression is restricted to the embryonic CNS and is detected in most, if not all, neurons. (C) Eph expression is eliminated in similarly staged homozygous Eph^x652 embryos. (D) The Ephrin^KG09118 P element insertion is inserted just downstream of the Ephrin transcription start site (Bellen et al., 2004). (E) In situ hybridization of Ephrin antisense RNA to a stage 15 wild-type embryo. Ephrin expression is detected in most if not all neurons within the CNS. (F) Ephrin expression is severely reduced in homozygous Ephrin^KG09118 embryos, suggesting that Ephrin^KG09118 is a hypomorphic loss-of-function mutation. Anterior is leftwards, dorsal is upwards.