Cloning of ABCC5 splice variants. (A) Identification of exon 5A, 5Aa and 5B within intron 5 of the ABCC5 gene. Exons of the ABCC5 gene are shown as open boxes, the retinal cDNA fragments as solid boxes. The mRNAGenBank represents a cDNA assembled from three human mRNA sequences deposited in GenBank [BC050744, CR590924 and CR619835]. The locations of primers used to PCR amplify ABCC5 cDNA fragments and the start and stop codon of full length ABCC5 are indicated by solid triangles above. Numbers refer to the respective exon number. The vertical line in exon 5Aa indicates an alternative splice donor site (B) Differential splicing of exons 5A, 5Aa and 5B generates three ABCC5 isoforms in the human retina, termed ABCC5_SV1, ABCC5_SV2 and ABCC5_SV3. RNA from human retina was RT-PCR amplified with primer pair F1/R3.