First insights into the expression of VAX2 in humans and its localization in the adult primate retina

• In humans VAX2 displays two isoforms (isoform-1 and -2); isoform-2 is enriched in the retina.
• Isoform-1 localizes to the nucleus whereas isoform-2 is widespread within the cell.
• VAX2 isoform-2 partially co-localizes with actin cytoskeletal filaments.
• In retina VAX2 is present in the nucleus or in the cytoplasm depending on the retinal cell type.
• An enrichment of VAX2 signal is detectable in the cone photoreceptors.

VAX2 is a transcription factor specifically expressed in the ventral region of the prospective neural retina in vertebrates and is required for ventral eye specification. Despite its extensive analysis in vertebrates, the biological role of VAX2 in the human is presently unclear. This study was undertaken to investigate VAX2 in humans aiming to gain new knowledge into its involvement in retinal function. Here, we report VAX2 gene expression and protein localization in cultured cells and adult retina. RT-PCR experiments indicated that VAX2 is enriched in neuronal tissues. Moreover, we identified a novel isoform most abundantly expressed in the retina. We termed the known transcript (NM_012476) isoform-1, and the newly identified transcript as isoform-2. Analysis of protein localization in cultured cells revealed that isoform-1 localizes to the nucleus and isoform-2 is widely expressed within the cell; partial co-localization of isoform-2 and actin filaments was also observed. In nonhuman primate retina VAX2 was seen either in the nuclear or in the cytoplasmic compartment depending on the retinal cell type. In addition, a noteworthy enrichment of the signal was observed in the outer segment of cone photoreceptors.Overall, this study provides the first insights into the expression of VAX2 in humans and its localization in the adult primate retina. Moreover, preliminary characterization of alternative variants suggests an involvement of VAX2 in multiple cellular pathways. Our findings raise the interesting possibility for further investigation of VAX2 in the retina in health and disease.