Zebrafish acetylcholinesterase is encoded by a single gene localized on linkage group 7 - Gene structure and polymorphism; Molecular forms and expression pattern during development

We cloned and sequenced the acetylcholinesterase gene and cDNA of zebrafish , Danio rerio. We found a single gene (ache) located on linkage group LG7. The relative organization of ache, eng2, and shh genes is conserved between zebrafish and mammals and defines a synteny. Restriction fragment length p olymorphism analysis was allowed to identify several allelic variations. We also identified two transposable elements in non-coding regions of the gen e. Compared with other vertebrate acetylcholinesterase genes, ache gene con tains no alternative splicing at 5' or 3' ends where only a T exon is prese nt. The translated sequence is 60-80% identical to acetylcholinesterases of the vertebrates and exhibits an extra loop specific to teleosts. Analysis of molecular forms showed a transition, at the time of hatching, from the g lobular G4 form to asymmetric A12 form that becomes prominent in adults. In situ hybridization and enzymatic activity detection on whole embryos confi rmed early expression of the acetylcholinesterase gene in nervous and muscu lar tissues. We found no butyrylcholinesterase gene or activity in Danio. T hese findings make zebrafish a promising model to study function of acetylc holinesterase during development and regulation of molecular forms assembly in vivo.