Cloning, expression, and functional characterization of the rat Pax6 5a orthologous splicing variant

• The rat Pax6 5a contains an additional 42 bp insertion at the paired domain.
• Pax6 5a is expressed in the rat E10 headfolds and not in the trunk of neurula.
• Retroviral Pax6 5a is expressed in the nucleus of mesenchymal stem cells.
• Pax6 5a shortly inhibits the proliferation of mesenchymal stem cells as Pax6.

Pax6 functions as a pleiotropic regulator in eye development and neurogenesis. Its splice variant Pax6 5a has been cloned in many vertebrate species including human and mouse, but never in rat. This study focused on the cloning and characterization of the Pax6 5a orthologous splicing variant in rat. It was cloned from Sprague–Dawley rats 10 days post coitum (E10) by RT-PCR and was sequenced for comparison with Pax6 sequences in the GenBank by BLAST. The rat Pax6 5a was revealed to contain an additional 42 bp insertion at the paired domain. At the nucleotide level, the rat Pax6 5a coding sequence (1311 bp) had a higher degree of homology to the mouse (96% identical) than to the human (93% identical) sequence. At the amino acid (aa) level, rat PAX6 5a shares 99.8% identity with the mouse sequence and 99.5% with the human sequence. The splice variant is preferentially expressed in the rat E10 embryonic headfolds and not in the trunk of neurula. Its effects on the proliferation of rat mesenchymal stem cells (rMSCs) were preliminarily evaluated by the MTT assay. Both pLEGFP-Pax6 5a-transfected cells and pLEGFP-Pax6-transfected cells exhibited a similar growth curve (P > 0.05), suggesting that the Pax6 5a has a similar effect on the proliferation of rMSCs as Pax6.