Abstract
Three cDNAs (OlGC3, OlGC4, and OlGC5) encoding membrane guanylyl cyclases were isolated from a medaka (Oryzias latipes) eye cDNA library. An open reading frame for OlGC3 predicted a protein of 1057 amino acids, and those for OlGC4 and OlGC5, 1134 and 1151, respectively. These proteins consist of an apparent signal peptide (21 residues for OlGC3, 50 residues for OlGC4, and 48 residues for OlGC5) and a single transmembrane domain that divides the protein into an amino-terminal extracellular domain and a carboxyl-terminal intracellular domain that further divides into a kinase-like domain and a cyclase catalytic domain. Phylogenetic analysis with amino acid sequences of OlGC3, OlGC4, and OlGC5, as well as those of other membrane guanylyl cyclases, indicated that OlGC3, OlGC4, and OlGC5 are members of the sensory organ-specific guanylyl cyclase family. Reverse transcription-polymerase chain reaction and Northern blot analyses demonstrated that OlGC3, OlGC4, and OlGC5 transcripts are present in the eye, which contains more cGMP than the other organs. In addition to being expressed in the eye, OlGC3 transcripts are also present in the brain, heart, liver, pancreas, and ovary, while OlGC4 is present in the liver and OlGC5 in the heart. Reverse transcription-polymerase chain reaction analysis with RNA from unfertilized eggs and embryos showed that OlGC3 and OlGC5 are expressed both maternally and zygotically, while OlGC4 is expressed only zygotically, and that the zygotic expression of these three genes is differentially activated. These results suggest a structural and functional diversity of sensory organ-specific guanylyl cyclases in vertebrates.
Highlights
The nucleotide sequence(s) reported in this paper has been submitted to the GenBankTM/EBI Data Bank with accession number(s) AB000899 (OlGC3), AB000900 (OlGC4), and AB000901 (OlGC5)
Analysis of cDNA clones for soluble Guanylyl cyclases (GCs) subunits have shown that each subunit contains a cyclase catalytic domain which is conserved in the membrane GCs [5,6,7,8]
We report that transcripts of two of the three medaka membrane GCs are present as maternal messages, and that each of these membrane GCs shows distinct expression patterns during embryogenesis and adulthood
Summary
The nucleotide sequence(s) reported in this paper has been submitted to the GenBankTM/EBI Data Bank with accession number(s) AB000899 (OlGC3), AB000900 (OlGC4), and AB000901 (OlGC5). Analysis of cDNA clones for soluble GC subunits have shown that each subunit contains a cyclase catalytic domain which is conserved in the membrane GCs [5,6,7,8]. To confirm further that the 5Ј-RACE product of OlGC3 corresponds to the authentic transcript, cDNA containing the overlapping region was amplified by RT-PCR with a pair of primers corresponding to nucleotide positions 1024 –1043 and 1380 –1400, cloned into pBluescript II KS(Ϫ) and sequenced.
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