Expression of Adh8 mRNA is developmentally regulated in Japanese medaka (Oryzias latipes)

We cloned two full-length alcohol dehydrogenase (ADH) cDNAs from the liver tissue of adult Japanese medaka (Oryzias latipes). The coding regions spanned 1134 and 1137 nucleotides (nt) and the deduced amino acid sequences shared 63.6% identity between them. Phylogenetic analysis of the deduced amino acid sequence data identified the 1137nt as an orthologue of mammalian Adh5 (Class III) and the 1134 nt as an ortholog of zebrafish Adh8 genes. Reverse transcriptase polymerase chain reaction (RT-PCR) analysis further showed that adult medaka Adh5 mRNA was expressed in all the organs tested (brain, eye, gill, GI, heart, liver, kidney, muscle, skin, spleen, testis and ovary) while Adh8 mRNA showed tissue-specific expression (eye, GI, liver, kidney, muscle and skin). Comparison of the Adh5 and Adh8 mRNA expression in eye, gill, liver, kidney and skin indicate that Adh8 mRNA copy numbers are higher in all these tissues compared to Adh5 mRNA expression. Both Adh5 and Adh8 mRNAs are expressed during embryonic development with Adh5 mRNA transcripts present with very high copy number throughout the development. However, Adh8 mRNA is expressed in very low copy numbers initially (∼1 h post fertilization; hpf) but begin to increase from 48 hpf to a level of ∼200-fold higher at hatching. Therefore, it appears that in Japanese medaka, the expression of Adh8 mRNA, not Adh5 mRNA, is developmentally regulated.