Genomic Structure and Expression of the Soluble Guanylyl Cyclase α₂ Subunit Gene in the Medaka Fish Oryzias latipes

A cDNA clone encoding the soluble guanylyl cyclase α₂ subunit was isolated from medaka fish (Oryzias latipes) and designated as OIGCS-α₂. The OIGCS-α₂ cDNA was 3192 bp in length and the open reading frame (ORF) encodes a protein of 805 amino acids. The deduced amino acid sequence has high similarity to that of the mammalian α₂ subunit gene except for the N-terminal regulatory domain. The C-terminal 5 amino acids, "RETSL", which have been reported to interact with the post synaptic density protein (PSD)-95 were conserved. An RNase protection assay with adult fish organs showed that OIGCS-α ₂ was expressed mainly in the brain and testis. The complete nucleotide sequence (about 41 kbp) of the OIGCS-α₂ genomic DNA clone isolated from a medaka fish BAC library indicated that the OIGCS-α₂ gene consisted of 9 exons and 8 introns. The 5′-flanking region and larger introns, such as introns 1, 4, and 7, contained the several fragments conserved in the nucleotide sequences of Rex6 (non-long terminal repeat retrotransposon), MHC class I genomic region, and OIGC1, the medaka fish homolog of the mammalian guanylyl cyclase B gene. Linkage analysis on the medaka fish chromosome demonstrated that the OIGCS-α₂ gene was mapped to LG13; this mapping position was different from those for the OIGCS-α₂ and OIGCS-β ₁ genes (LG1).