Molecular cloning and genomic organization of the mouse AE2 anion exchanger gene

The molecular organization of the AE2 (SLC4A2) gene, a member of the multig ene family encoding sodium-independent chloride/bicarbonate anion exchanger s, has previously been described in both humans and rats. In these two spec ies, AE2 shows alternate promoter usages and tissue-specific expression of isoforms in a similar, but not identical, fashion. Here we report the molec ular cloning and organization of the entire mouse AE2 gene. The gene consis ts of 23 exons and 22 introns and spans about 17 kb. Moreover, it drives tr anscription of N-terminal truncated isoforms from alternate promoter sequen ces in a way analogous to that described for rat and/or human orthologs. Th us, sequences within intron 2 function as overlapping alternate promoters f or truncated isoforms AE2b(1) and AE2b(2), and sequences of intron 5 drive transcription of isoforms AE2c(1) and AE2c(2). Each of these variants has a specific alternative first exon, while remaining exons are common to the c omplete form of the message AE2a, the diversity at 5' leading to different N- termini in corresponding encoded proteins. As expected, mouse AE2 promot er sequences and the patterns of tissue expression of AE2 isoforms resemble rat counterparts more closely than human ones. (C) 2000 Academic Press.