The organization of the human gene NCX1 encoding the sodium-calcium exchanger

The intron-exon organization of the human Na/Ca-exchanger gene NCX1 and of the N-terminal half of the related gene NCX2 has been determined. The NCX1 gene consists of 12 exons spread over 200 kb on chromosome 2 close to STS D2S2328 and encodes a 6.2-kb transcript. Both NCX1 and NCX2 feature an unusual 1.8-kb exon, containing two-thirds of the protein coding sequence and a similar area of the coding sequences split into several small exons, displaying tissue-specific alternative splicing. The similar intron positions in the "cardiac" (NCX1) and "brain" (NCX2) mammalian exchanger genes suggest their origin from the recent duplication and translocation of a common ancestral gene, a putative precursor of which has been identified in the nematode Caenorhabditis elegans.