| Summary: | The ability to synthetize ascorbic acid has been lost multiple times in animals always due to mutations in the terminal gene (GULO) of the Vitamin C synthesis pathway. This suggests that the other genes of the pathway perform other essential functions besides participating in the synthesis of Vitamin C. The study of Regucalcin (gene involved in the penultimate step of the pathway) in lineages where GULO has been lost long time ago can give insight into the biological role of this gene besides its usual involvement in the Vitamin C pathway. In humans, changes in Regucalcin gene expression have been involved in obesity, diabetes and cancer. In Drosophila melanogaster, besides Regucalcin, there is also a paralog (Dca) that shows signs of positive selection at the protein level, that is greatly overexpressed when flies are cold-acclimated and shows expression levels that are correlated with latitude. In order to understand the multiple roles played by Regucalcin and its paralogs, in this project, a combination of evolutionary and functional analyses was used. The evolutionary analysis, where all annotated animal genomes were used, showed that the Regucalcin gene is not present in all animals, that it is often duplicated in Protostomes (suggesting subfunctionalization), but not in Deuterostomes and that it was lost multiple times independently. An evolutionary correlation between the presence/loss of the Regucalcin/GULO/SVCT genes in the animal kingdom is also observable. In D. melanogaster, using RNAi strains, it was demonstrated that Regucalcin and Dca are essential genes. And lastly, a bioinformatics analysis revealed positively selected amino acid sites at the Regucalcin protein lid, but also at the new putative interaction domain.
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