Expression of exon -1 and extended exon 0 mRNAs in stomach and SW1353 cell line. Exons are represented as boxes, PCR primers are indicated as arrows above exons. A. Amplicons spanning the extended exon 0 to exon 4 of the ghrelin gene. A major 1064 base pair amplicon, corresponding to a full-length transcript, is expressed in the human stomach (HS). The SW1353 chondrosarcoma cell line expresses a complex pattern of alternatively-spliced products, which may result from promiscuous splicing of exon 0. B. Exon -1 to 4 amplicons sequenced from the human stomach. Transcripts have been grouped into three major types (I, II and III). Group I amplicons include all preproghrelin exons (exons 1–4), but differ in the length of sequence upstream of exon 1 (the 5' UTR of preproghrelin). Group II transcripts contain exon -1, exon 4 and various combinations of exons downstream of exon 1 (exon 2 to 4), but lack exon 0 and 1. Group III transcripts contain alternative exon -1 and 4 (exon -1* and 4*, respectively) in addition to two novel exons (exon 2* and 2**) in intron 2 of the ghrelin gene.