Contents lists available at ScienceDirect Mechanisms of Ageing and Development journal homepage: www.elsevier.com/locate/mechagedev    

Mechanisms of Ageing and Development

journal homepage: www.elsevier.com/locate/mechagedev

functional EXO1 promoter variant is associated with prolonged life in centenarians

Almut Nebel a,1, Friederike Flachsbart a,1, Andreas Till a,1, Amke Caliebe b, He´le`ne Blanche´ c, Alexander Arlt d, Robert Ha¨sler a, Gunnar Jacobs a, Rabea Kleindorp a, Andre Franke a, Binghui Shen e, Susanna Nikolaus f,g, Michael Krawczak b,g, Philip Rosenstiel a, Stefan Schreiber a,f,*

aInstitute of Clinical Molecular Biology, the Christian-Albrechts-University, Kiel, Germany bInstitute of Medical Informatics and Statistics, the Christian-Albrechts-University, Kiel, Germany cFondation Jean Dausset-Centre d’Etude du Polymorphisme Humain (CEPH), Paris, France dMolecular Gastroenterology, the Christian-Albrechts-University, Kiel, Germany eDepartment of Radiation Biology, City of Hope National Medical Center and Beckman Research Institute, Duarte, CA, fDepartment of General Internal Medicine, the Christian-Albrechts-University, Kiel, Germany gPopgen Biobank, the Christian-Albrechts-University, Kiel, Germany

A B S T R A C T

Human longevity is heritable with a genetic component of 25–32%. Variation in genes regulating the levels of somatic maintenance and DNA repair functions is thought to modulate the aging process and to contribute to survival at advanced age. We tested 92 non-synonymous SNPs in 49 DNA repair genes for a possible association with longevity in a sample of 395 German centenarians and 411 controls. The obtained association signal in exonuclease 1 (EXO1) was further investigated by fine mapping and mutation detection, leading to the identification of the functionally relevant SNP rs1776180. Our detailed analyses revealed that the C allele of this promoter SNP is significantly enriched in female centenarians. This finding replicated in 455 female French centenarians and 109 controls. The C allele leads to the loss of a binding site for the basic helix–loop–helix transcription factor E47, resulting in higher EXO1 expression. Thus, we have detected a hitherto undescribed role for E47 as a negative regulator of EXO1 transcription and a genetic variant in the EXO1 promoter that counteracts the E47- mediated repression of the gene. Given the survival advantage that is associated with the C allele of rs1776180, EXO1 can be considered a candidate for a novel longevity-enabling gene.

resolve DNA damage have evolved as highly conserved longevity assurance mechanisms (Hasty, 2005). Another line of evidence that links DNA repair with aging is that many of the human progeria disorders, such as Werner Syndrome, are caused by mutations in genes involved in DNA maintenance (reviewed by Hasty, 2005). Similarly, studies of mouse models show that genetic defects affecting genomic integrity underlie several of the accelerated aging phenotypes (Hasty, 2005; Lombard et al., 2005).

1. Introduction

There is increasing evidence that somatic mutations progres- sively accumulate with age in various species, including humans (Hasty et al., 2003; Vijg, 2000). A wide range of exogenous agents (e.g. UV-radiation) and by-products of cellular metabolism (e.g. reactive oxygen species) are known to harm genetic material. In addition, mutations can arise from spontaneous replication errors (Hasty, 2005). Since DNA damage may result in dysregulated cellular processes, apoptosis, oncogenic transformation, genomic instability and senescence, maintenance systems are critical for both cellular and organismal homeostasis and survival (Lombard et al., 2005). Therefore, numerous pathways that either prevent or

These findings support the notion that variation in genes regulating the levels of somatic maintenance and DNA repair functions could also modulate the normal aging process and contribute to longevity (Kirkwood, 2005). In humans, it is conceivable that the more efficient these survival mechanisms are, the more likely would an individual be to attain old age in good physical and cognitive condition, leading not only to an increase in their life span but also in their ‘health span’. In fact, it has been postulated that long-lived individuals, who are often characterized by a decelerated aging process and a delayed onset of age-related diseases (Hitt et al., 1999), are enriched for favourable variants in longevity-enabling genes compared to younger controls (Perls

* Corresponding author at: Institute of Clinical Molecular Biology, Christian- Albrechts-University and University Hospital Schleswig-Holstein, Schitten- helmstraße12,24105Kiel,Germany.Tel.:+494315972350;fax:+494315972196. E-mail address: s.schreiber@mucosa.de (S. Schreiber).

0047-6374/$ – see front matter  2009 Elsevier Ireland Ltd. All rights doi:10.1016/j.mad.2009.08.004

et al., 2002). A recent twin study strengthens this hypothesis by showing that the overall genetic contribution (25–32%) to human life expectancy is minimal before the age of 60, but becomes particularly important for survival at a very advanced age (Hjelmborg et al., 2006). So far, variation in only two genes, apolipoprotein E (APOE) (Christensen et al., 2006) and forkhead box O3A (FOXO3A) (Anselmi et al., 2009; Flachsbart et al., 2009; Willcox et al., 2008), has been found to be repeatedly associated with longevity in different populations.