title: Seawater acclimation and inositol monophosphatase isoform expression in the European eel (Anguilla anguilla) and Nile tilapia (Orechromis niloticus).
abstract: Inositol monophosphatase (IMPA) is responsible for the synthesis of inositol, a polyol that can function as an intracellular osmolyte helping re-establish cell volume when exposed to hypertonic environments. Some epithelial tissues in euryhaline teleosts such as the eel and tilapia encounter considerable hyperosmotic challenge when fish move from freshwater (FW) to seawater (SW) environments; however, the roles played by organic osmolytes, such as inositol, have yet to be determined. Syntenic analysis has indicated that, as a result of whole genome- and tandem-duplication events, up to six IMPA isoforms can exist within teleost genomes. Four isoforms are homologs of the mammalian IMPA1 gene, and two isoforms are homologs of the mammalian IMPA2 gene. Although the tissue-dependent isoform expression profiles of the teleost isoforms appear to be species-specific, it was primarily mRNA for the IMPA1.1 isoform that was upregulated in epithelial tissues after fish were transferred to SW (up to 16-fold in eel and 90-fold in tilapia). Although up-regulation of IMPA1.1 expression was evident in many tissues in the eel, more substantial increases in IMPA1.1 expression were found in tilapia tissues, where SW acclimation resulted in up to 2,000-fold increases in protein expression, 16-fold increases in enzyme activity and 15-fold increases in tissue inositol contents. Immunohistochemical studies indicated that the tissue and cellular distribution of IMPA1.1 protein differed slightly between eels and tilapia; however, in both species the basal epithelial cell layers within the skin and fin, and the branchial epithelium and interstitial cells within the kidney, exhibited high levels of IMPA1.1 protein expression.
authors.affiliation: School of Medicine, University of St. Andrews, St. Andrews, United Kingdom;
authors.forename: Svetlana
authors.initials: S
authors.lastname: Kalujnaia
authors.forename: Steven A
authors.initials: SA
authors.lastname: Gellatly
authors.forename: Neil
authors.initials: N
authors.lastname: Hazon
authors.forename: Alfredo
authors.initials: A
authors.lastname: Villasenor
authors.forename: Paul H
authors.initials: PH
authors.lastname: Yancey
authors.forename: Gordon
authors.initials: G
authors.lastname: Cramb
mesh_terms: D000064:Acclimatization; D000818:Animals; D023681:Cichlids / Q000235:genetics / Q000378:metabolism*; D004524:Eels / Q000235:genetics / Q000378:metabolism*; D004790:Enzyme Induction; D004847:Epithelial Cells / Q000201:enzymology*; D029941:Fish Proteins / Q000235:genetics / Q000378:metabolism*; D020869:Gene Expression Profiling; D007150:Immunohistochemistry; D007294:Inositol / Q000096:biosynthesis; D007527:Isoenzymes; D010744:Phosphoric Monoester Hydrolases / Q000096:biosynthesis* / Q000235:genetics; D010802:Phylogeny; D012333:RNA, Messenger / Q000096:biosynthesis; D012623:Seawater; D013045:Species Specificity; D015854:Up-Regulation; D014882:Water-Electrolyte Balance
chemical_list: D029941:Fish Proteins; D007527:Isoenzymes; D012333:RNA, Messenger; D007294:Inositol; D010744:Phosphoric Monoester Hydrolases; C021822:myo-inositol-1 (or 4)-monophosphatase
keywords: Anguilla anguilla; Oreochromis niloticus; gene synteny; inositol monophosphatase; osmolyte; osmoregulation; teleost