A novel Acetyl-CoA synthetase short-chain subfamily member 1 (Acss1) gene indicates a dynamic history of paralogue retention and loss in vertebrates

Acetyl-CoA short chain synthetases (ACSSs) are key enzymes in the activation of fatty acids through the formation of thioesters with CoA. Three subfamily members are currently recognized in the human genome, ACSS1. ACSS2 and ACSS3, all single copy genes. The mitochondrial isoform. Acss1, plays a key role in the metabolism of acetate for energy production. While the single copy condition has been accurately established in humans, the evolutionary history of the Acss1 subfamily in vertebrates has yet to be elucidated, in particular, the isoform diversity, origin and function. Through genome database mining we analyzed the diversity of Acss1 isoforms in vertebrate classes. We detected the presence of a novel Acss1 isoform, which we name Acss1B. This new gene, Acss1B, has a curious phylogenetic distribution being found in teleosts (except zebrafish), sauropsids (birds and reptiles) and probably chondrichthyes. In contrast Acss1A is found in all the investigated species, except the teleost medaka. By means of comparative genomics and phylogenetics we show that Acss1A and Acss1B were generated in the quadruplication of the vertebrate genome. In effect, we find that amphioxus, a pre-genome duplication chordate, has a single Acss1 gene in a genomic region equally related to a quadrupled vertebrate genomic set. Consequently, Acss1B has been lost in some teleosts, amphibians and mammals, while Acss1A is probably absent in medaka. The reported findings illustrate an especially dynamic pattern of paralogue retention and independent loss in vertebrate species involving the Acss1 subfamily, whose functional consequences in energy metabolism are as yet unknown. (C) 2012 Elsevier B.V. All rights reserved.