Figure I for BOX 1. Schematic representation of human ZnT8 transcripts and proteins.

A. Exons comprising the 5′ UTR and initiator methionine of the 5 NCBI RefSeq transcripts are shown. Coding exons are shown in green and the 30bp exon 6 that contains 2 in-frame stop codons in red, or pink in the case of transcript 3 that lacks the start site in exon 5 and could give rise to a truncated product from a downstream in frame ATG in exon 7. Exons 2 and 5 contain multiple splice acceptor sites. All transcripts contain exons 8–13. The ZnT8 isoform potentially encoded by each transcript is shown. It should be noted that most studies of the expression of SLC30A8 mRNA in non-β cell tissues use primer pairs that will not distinguish the various transcripts. B. The domain structure of the two isoforms are shown. The light blue shapes indicate domains implicated in Zn2+ binding, and the bracket the approximate location of the polymorphic residue 325.