Heat-Shock Protein 70 Genes and Human Longevity



a b c SINGH, STEEN KØLVRAA, PETER BROSS, d c e CHRISTENSEN, NIELS GREGERSEN, QIHUA TAN, a,h f BIRK JENSEN, HANS EIBERG, AND g I. S. RATTAN

Department of Human Genetics, University of Aarhus, Aarhus, Denmark

ABSTRACT: We have studied the association of three single nucleotide polymorphisms (SNPs) present in the three HSP70 (heat-shock protein) genes on 6p21 with human longevity. The availability of biological sam- ples from various population cohorts in Denmark has given us the op- portunity to try novel methods of gene association with human longevity. A significant association of one haplotype with male longevity was ob- served. Furthermore, a significant difference in the survival of the car- riers of the different genotypes in females was observed. We also found an age-dependant decline in the ability of peripheral blood mononuclear cells to respond to heat stress in terms of Hsp70 induction.

Human longevity is a multifactorial trait with both genetic and environ- mental factors playing an important role in its manifestation. Studies in twins on the genetic basis of human longevity indicated that approximately 25% of the observed differences in life expectancy are due to genetic variations.1,2 The conventional approach for identifying longevity-determining genes has been by population-based association studies, where a group of long-lived in- dividuals (LLIs) is compared to a group of young individuals for differences in the gene and genotype frequencies of candidate genes.3 This approach, though common, has several limiting factors.3

Heat-shockproteins(Hsps)4 are a part of the cellular safety and rescue mechanisms. At the cellular all organisms respond to stress by synthesizing Hsps at the expense of proteins. This phenomenon is called “heat-shock response” (HSR),5 protects cells from subsequent damage and aids them to counteract the of the stress. The capacity to respond rapidly to stress at the gene level mines the adaptive and, therefore, the survival capacity and longevity of organism.6 One way of indicating the relationship between human and stress response is to demonstrate an association between single polymorphisms (SNPs) in Hsp genes (HSP) and longevity7,8 or parameters

Of all the various heat-shock proteins, Hsp70 is the most prominent and best characterized of the stress protein families. Hsp70 is a highly inducible and most actively synthesized protein in the cell upon heat shock. In humans there are 11 different isoforms of HSP70 encoded by different genes located at dispersed loci. Three of the 11 isoforms of HSP70 are localized within the major histocompatibility complex (MHC) class III region on chromosome 6p21.10 These are intron-less HSP70A1A (HSP70-1), HSP70A1B (HSP70-2), and HSP70A1L (HSP70-Hom)11 genes. They display a very high sequence similarity but differ in their regulation. We have studied the association of three SNPs, one in each MHC-linked HSP70 gene, with human longevity, survival, and parameters of aging (TABLE 1).

With the ever-increasing number of elderly persons in the population and in well-maintained health and population registries, 12,13 the availability of a unique set of biological samples for research from various well-established

SINGH et al.: HSP70 AND LONGEVITY IN DENMARK

1. SNPs in HSP70 genes studied for their association with human longevity

aVariation may affect the substrate specificity and chaperone activity of the Hsp70.

TABLE 2. Different population cohorts in Denmark used for studying the association of HSP70 genes with human longevity

population databases, and from different age-related cohorts, in Denmark, pro- vides a rare opportunity to perform novel population-based genetic association studies by mitigating many of the limiting factors 9,14–17 (TABLE 2). For our research we have used DNA samples from 426 participants from the

(1) Longitudinal Study of Ageing Danish Twins (LSADT), which is the old- est twin registry in the world.18 These twins, sampled in 1999, are between the ages of 70 and 91 years (mean age 75.6 years), and have been catego- rized according to the absence or presence of various age-related diseases and for various age-related parameters including scores of physical and cognitive

time polymerase chain reaction on the LightCycler system (Roche Sciences), which allows monitoring of the amplification of the PCR in real time, using fluorescent labeled oligonucleotide probes (TIB BIOL, Germany) and primers (DNA Technology A/S, Denmark) specific each SNP (sequences of primers and probes can be provided on request).

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computer program PHASE (Version 2.0.2), which implements a Bayesian sta- tistical method for reconstructing haplotypes from population data.22,23 Pair-wise linkage Disequilibrium (LD) among the three markers was calcu- lated using Java LINkage Disequilibrium Plotter (JLIN) (http//www.genepi.

Blood samples were also collected from a group of young (mean age years) and middle-aged individuals (mean age 56.3 years). Mononu- cells (monocytes and lymphocytes) were isolated and then studied ◦ age-related HSR after giving 1 h of heat shock for 42 C followed by h of recovery. The amount of induced protein was quantified by using a cytometer.

RESULTS AND DISCUSSION

The gene and genotype frequency of the three SNPs was found to be in = a Hardy–Weinberg equilibrium. In LSADT “Self-rated health” (P 0.0046) = and “Relative self-rated health” (P 0.018), which represent an individual’s overall sense of physical well-being and which have been shown to be both predictors of survival at older ages and better indicators of future survival than objectively measured health status, were associated with heterozygosity for − 110A> C polymorphism in the promoter region of HSP70-1.9 The molecular haplotype analyses on Danish family samples have revealed