Generation of the Otx2OG allele. a. The structure of targeting vector (first line), Otx2 wild type locus (second line), targeted OGN allele after homologous recombination (third line) and OG allele after removal of the Neo cassette by FLP recombinase (fourth line) is presented. Gray boxes are Otx2 coding regions, whites boxes are Otx2 5' and 3' UTR regions, yellow box is PGK-Neo selection cassette, green box is muGFP cDNA. Red triangles are FRT sites. Bent arrows symbolize the three main transcription starts sites known for Otx2 gene [19, 32]. Dotted lines show BamH I fragments detected by southern blot analysis using probe represented by a thick line. PCR primers used are indicated by arrows. Product obtained with A and B primers is shown. Scale bar and sizes of fragments are indicated. b. PCR analysis of NeoR ES clones using primers A and B showing two non-homologous (N) and one homologous (H) recombinants. c. Southern blot analysis using BamH I digested genomic DNA and probe indicated in a of wild type and homologous recombinant clones. Genotypes are indicated. d. PCR genotyping of mice produced from Otx2+/OGES cells. Analyse was done using C, D and E primers. Sizes, schematic representations of amplified fragments (see part a for legend) and deduced genotypes are indicated.