Alternative splicing in the aldo-keto reductase superfamily: implications for protein nomenclature.

The aldo-keto reductase superfamily contains 173 proteins which are present in all phyla. Examination of the human and mouse genomes has identified that in some instances a single AKR gene can give rise to alternatively spliced mRNA variants which in some cases can give rise to more than one protein isoform. This is currently well documented in the AKR6A subfamily which contains the β-subunits of the voltage-gated potassium ion channels. With the emergence of second generation sequencing it is likely that the occurrence of transcript variants and protein isoforms from a single AKR gene may become common place. To deal with this issue we recommend that the Ensembl data-base nomenclature be used to annotate the transcript variants from a single AKR gene. However, since multiple transcript variants could give rise to either the same or multiple protein isoforms from the same AKR gene we also propose to expand the nomenclature of the AKR protein superfamily, so that when a protein isoform is shown to be expressed and is functional it would be assigned the standard AKR name followed by a "period or full-stop" and a number for that unique isoform. Numbers will be assigned chronologically and linked to the respective transcripts annotated in Ensembl e.g. AKR6A5.1 (Kvβ2.1) (AKR6A5-001, -006 and -201), followed by AKR6A5.2 (Kvβ2.2) (AKR6A5-002,-202). This nomenclature is expandable and it enables multiple protein isoforms to be assigned to their respective transcripts when they arise from the same AKR gene or for a single protein isoform to be assigned to multiple transcripts when the transcripts encode the same AKR protein.