Fig. 5. Aberrant splicing of the Vegf-lacZ fusion RNA results in loss of exon 8-coding sequences and the complete IRES. (A) Schematic representation of mouse VEGFA isoforms (VEGF 188, VEGF 164 and VEGF 120) (, VEGFR1 binding site; , VEGFR2 binding site) and the predicted Vegf-lacZ fusion RNA followed by the actual RNA generated by aberrant splicing (primers used in RT-PCR analysis are indicated as arrows). (B) Sequence comparison of the VEGFA exon7/8 junction (top) and the exon 7/lacZ splice junction of the Vegf^lo RNA (bottom). The out-of-frame lacZ start codon and the stop codon, which terminates the translation of the fusion protein, are underlined. (C) RT-PCR analysis of the Vegf^lo allele (lo, lane 3). Oligo dT-primed cDNA was amplified using the primers indicated in A, amplification from the Vegf^lacZKI-allele is shown for comparison (KI, lane 2). (D) Quantitative analysis of VEGFA-immunoreactive material in 8.5 dpc mouse embryos of different genotypes. Amounts of VEGFA immunoreactive material are given in pg/ml.