Structure and chromosomal mapping of the mouse P2X₃ gene

P2X₃ is one of seven cloned ATP-gated non-selective cation channels. We have isolated a full-length mouse P2X₃ gene from a phage λ-129/Sv genomic library. The gene consists of 12 exons spanning a locus of approximately 40 kb. No significant similarities have been found between the genomic organisation of the mouse P2X₃ gene and genes encoding other ion channels. The encoded mouse P2X₃ protein consists of 397 amino acids and shows 99% identity with rat P2X₃. Using RNase protection and primer extension assays, multiple transcription initiation sites have been mapped in the mouse P2X₃ promoter to a region 162-168 bp upstream of the translation initiation codon. The P2X₃ gene has been mapped to mouse chromosome 2p by fluorescence in situ hybridisation. The RAG locus-associated gene T160 is located 1.8 kb upstream of the transcription start site of mouse P2X₃ gene. The promoter region of the mouse P2X₃ gene lacks a conventional TATA and CCAAT consensus sites, and initiator elements. P2X₃ is the first member of the P2X₃ gene family to be completely characterised.