A Polymorphism of the YTHDF2 Gene Located in an Alu-Rich Genomic Domain Is Associated With Human Longevity

1 1 1 1 Maurizio Cardelli, Francesca Marchegiani, Luca Cavallone, Fabiola Olivieri, 1 1 1 Simona Giovagnetti, Elena Mugianesi, Raffaella Moresi, 1 1,2,3,4 Rosamaria Lisa, and Claudio Franceschi

1Department of Gerontological Research, Italian National Research Center on Aging (INRCA), Ancona, Italy. 2Interdipartimental Centre L. Galvani (CIG), and 3Department of Experimental Pathology, University of Bologna, Italy. 4ER GenTech Laboratory, University of Ferrara, Italy.

The uneven distribution of Alu repetitive elements in the human genome is related to specific functional properties of genomic regions. We report the identification of a locus associated with human longevity in one of the chromosomal regions with the highest density of Alu elements, in 1p35. The locus, corresponding to a (TG)n microsatellite in the YTHDF2 gene, was identified by characterizing an ‘‘anonymous’’ marker detectable through inter- Alu fingerprinting, which previously evidenced an increased homozygosity in centenarians. After genotyping 412 participants of different ages, including 137 centenarians, we confirmed the increased homozygosity in centenarians at this locus, and observed a concomitantly increased frequency of the most frequent allele and the corresponding homozygous genotype. Remarkably, the same genotype was associated with increased YTHDF2 messenger RNA levels in immortalized lymphocytes. Finally, YTHDF2 messenger RNA resulted to be mainly expressed in testis and placenta. The data suggest a possible role of this locus in human longevity.

are much more rich in potential methylation sites compared to non-Alu human genomic DNA, and their methylation status is likely to have an influence on the methylation of surrounding regions (18,23). On the whole, Alu distribution appears to be associated with specific functional properties of genomic regions (21).

longevity is considered a complex trait influenced by many environmental and genetic factors. The genetics of human longevity has been addressed by association studies on well-characterized candidate genes (1–12) as well as by studies aimed to discover new longev- ity genes through the cloning of genes differently expressed in centenarians (13) or through large scale genome scanning (14), as in the case of the European Union Genetics of Healthy Aging (GEHA) project (15). We also explored a different approach, designed to screen multiple loci in peculiar genomic regions particularly rich in Alu sequences (16). These repetitive elements of 300 bp represent, with more than one million copies, the most abundant human SINEs (Short Interspersed Nuclear Elements), i.e., non- autonomous retrotransposons transcribed by RNA poly- merase III. Alu repetitive elements are present on all human chromosomes, but a great variability in their density and genomic distribution has been observed (17). It is interesting to note that Alu-rich genomic regions are considered to be potentially unstable, in germline as well as in somatic cells, due to unequal recombination events (18–20). Moreover, Alu density positively correlates with gene density (21) and, more specifically, these repetitive elements are found to be highly clustered near genes involved in metabolism, trans- port, and signaling processes (22). Genes contained in Alu- rich regions could also be hypothesized to have a peculiar sensitivity to epigenetic regulation, given that Alu elements

In our previous work (16), we set up an Alu-based DNA fingerprinting method which, using Alu-specific primers (inter-Alu polymerase chain reaction [PCR]), allowed us to preferentially scan multiple genomic regions characterized by high Alu density and to detect genetic markers of ‘‘anonymous’’ loci putatively associated with human longevity. The inherent assumption of such a method is that it amplifies DNA fragments located between two closely spaced (usually no more than 1 kb) Alu sequences with opposite orientation, a situation which occurs most frequently in Alu-rich genomic regions.

The aims of the present work were the following: (i) to identify and characterize the genomic locus corresponding to the ‘‘anonymous’’ QM-376-400 inter-Alu marker, pre- viously reported to show an increased homozygosity in centenarians (16); (ii) to assess the existence of a genotype– longevity association at this locus in a new, independent set of very old participants (centenarians) and younger controls; and (iii) to collect preliminary information about the functional role of the genetic variants of this locus eventually associated with longevity.

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