Schematic drawing (not to scale) of cloned and sequenced CCK2R variants. A) grey boxes correspond to amino acid sequences (exon 4 and 5) of the wt CCK2R [GenBank:NM176875] and B) CCK2i4svR splice variant receptor (exon 4, intron 4, exon 5) [GenBank:AF441129]. C) CCK2R splice variant consisting of exon 4, the first five N-terminal amino acids of intron 4, and one base truncation at the C-terminal end in exon 5 [GenBank:DQ335648]. D) CCK2R splice variant consisting of exon 4, a deviating and truncated intron 4 (black boxes indicate that a frame-shift mutation has occurred generating putative amino acids deviating from the wild-type sequences). [GenBank:DQ335649]. E) [GenBank:DQ335650] and F) [GenBank:DQ335651] CCK2R splice variants with deviating amino acid sequences in intron 4 and exon 5 compared to CCK2R (wt) and CCK2i4svR. Amino acid sequences deviating from previously reported CCK2R and CCK2i4svR sequences are indicated using the single letter amino acid code. The positions of in frame stop codons yielding tentatively truncated CCK2 receptors in D) and F) are indicated by an asterix.