A Genetic Variant of ASCT2 Hampers In Vitro RNA Splicing and Correlates with Human Longevity

Given the role of amino acid regulation for physiological and pathological cell proliferation, we investigated whether the variability of solute carrier family 1, member 5 (SLC1A5, namely ASCT2), encoding for ASCT2 protein, a major glutamine transporter, is related to longevity. A total of 607 differently aged unrelated individuals, 351 very old subjects (85 years, range 85-106 years, mean age 93.82 +/- 4.44 years) and 256 younger controls (<85 years, range 64-84 years, mean age 73.60 +/- 5.70 years) were analyzed. Single-nucleotide polymorphisms (SNPs) were selected by a tagging SNP approach prioritizing those most likely to be of functional relevance. Genotyping was carried out using iPLEX Gold Genotyping Assay (Sequenom MassARRAY), and a logistic regression analysis was used to examine the associations between genotypes and the longevity phenotype. Age-associated variants were predicted to be involved in the alteration of an exonic splicing enhancer (ESE) site by Human Splicing Finder (HSF) v.3. Minigene constructs containing the alleles associated with longevity allowed the assessment of the functional effects of the polymorphisms. Two polymorphisms were found associated with human longevity (rs3027958 and rs1644343). Indeed, the major alleles of both SNPs positively influence the probability to become long-lived. In vitro assays suggested that the minor allele of rs3027958 alters an ESE site, thus inducing intron retention. We provide evidence about the functional role of intronic variants of the ASCT2 gene in hampering the splicing process, and the effect of these variants on survival, confirming the crucial role played by this amino acid transporter in modulating longevity.