Molecular and functional studies of tilapia (Oreochromis mossambicus) NMDA receptor NR1 subunits.

NMDA (N-methyl-d-aspartate) receptor, a subclass of the ionotropic glutamate receptors, participates in synaptic transmission and plays important roles in various higher brain functions in the vertebrate central nervous system. Here, we report the cloning of two NR1 subunits of tilapia (Oreochromis mossambicus). Phylogenetic analysis strongly supports that the two tilapia NR1 genes are paralogous, resulting from a gene duplication event in the teleost lineage.

The mutually exclusive flip and flop exons of AMPA receptor genes were derived from an intragenic duplication in the vertebrate lineage.

The incomplete correlation between the organismal complexities and the number of genes among eukaryotic organisms can be partially explained by multiple protein products of a gene created by alternative splicing. One type of alternative splicing involves alternative selection of mutually exclusive exons and creates protein products with substitution of one segment of the amino acid sequence for another. To elucidate the evolution of the mutually exclusive 115-bp exons, designated flip and flop, of vertebrate AMPA receptor genes, the gene structures of chordate (tunicate, cephalochordate, and vertebrate) and protostome (Drosophila and Caenorhabditis elegans) AMPA receptor subunits were compared.