Figure 5. Identification of novel mouse Slc4a7 transcripts encoding MIPL-NBCn1 and MDEL-NBCn1.

(A) Structure of mouse Slc4a7 gene. Slc4a7 contains two alternative promoters as demonstrated previously⁹. In addition, the gene contains 29 exons, of which exon 3 was newly identified in the present study. # indicates cassette exons (exon 3,8,9, 11,16,28). (B) Nucleotide sequence of exon 3 (upper case) and the flanking intron (lower case) of mouse Slc4a7. The underlined (blue) indicate the cryptic splicing donor and acceptor. The “ATG” in red indicates the alternative start codon for the “MIPL” motif. (C) Diagram to show the exon structure of Slc4a7 transcripts encoding the three different types of Nt ends of NBCn1. The grayed boxes represent the coding regions, whereas the open boxes represent the non-coding regions. The originally-described transcripts, predicted to encode MEAD-NBCn1, are derived from promoter P1. The originally-described MERF- as well as the newly identified MIPL- and MDEL-NBCn1 are derived from promoter P2. In the present study, exon 3 was identified only in the transcripts derived from promoter P2 of Slc4a7.