Fig. 1. Generation of Vax2 mutant mice. (A) Targeted deletion of exon 2 (EX2) of the Vax2 gene by homologous recombination in ES cells. The PGK-Neo expression cassette introduces two novel HindIII sites and removes two BamHI restriction sites. The probes used for Southern-blot analysis are also shown (hatched boxes). Tk, thymidine kinase; B, BamHI; H, HindIII; RI, EcoRI; X, XbaI. (B) Southern blot analysis of genomic DNA from wild-type (+/+), heterozygous (–/+) and homozygous (–/–) mutant mice, hybridised with the 3' probe indicated in A. (C) RT-PCR analysis of total retina RNA from wild-type and Vax2^–/– mice using primers 32F and 7R located, respectively, in the first and in the third coding exons of the Vax2 gene. The amplified RT-PCR fragment in the Vax2^–/– lane does not contain exon 2 (see the text for more details). Lanes 1 and 2, molecular weight markers.