Somatic, positive and negative domains of the Center for Epidemiological Studies Depression (CES-D) scale: a meta-analysis of genome-wide association studies.

BACKGROUND: Major depressive disorder (MDD) is moderately heritable, however genome-wide association studies (GWAS) for MDD, as well as for related continuous outcomes, have not shown consistent results. Attempts to elucidate the genetic basis of MDD may be hindered by heterogeneity in diagnosis. The Center for Epidemiological Studies Depression (CES-D) scale provides a widely used tool for measuring depressive symptoms clustered in four different domains which can be combined together into a total score but also can be analysed as separate symptom domains. METHOD: We performed a meta-analysis of GWAS of the CES-D symptom clusters. We recruited 12 cohorts with the 20- or 10-item CES-D scale (32 528 persons). RESULTS: One single nucleotide polymorphism (SNP), rs713224, located near the brain-expressed melatonin receptor (MTNR1A) gene, was associated with the somatic complaints domain of depression symptoms, with borderline genome-wide significance (p discovery = 3.82 × 10-8). The SNP was analysed in an additional five cohorts comprising the replication sample (6813 persons). However, the association was not consistent among the replication sample (p discovery+replication = 1.10 × 10-6) with evidence of heterogeneity. CONCLUSIONS: Despite the effort to harmonize the phenotypes across cohorts and participants, our study is still underpowered to detect consistent association for depression, even by means of symptom classification. On the contrary, the SNP-based heritability and co-heritability estimation results suggest that a very minor part of the variation could be captured by GWAS, explaining the reason of sparse findings.

Gene transcripts associated with muscle strength: a CHARGE meta-analysis of 7,781 persons.

Lower muscle strength in midlife predicts disability and mortality in later life. Blood-borne factors, including growth differentiation factor 11 (GDF11), have been linked to muscle regeneration in animal models. We aimed to identify gene transcripts associated with muscle strength in adults. Meta-analysis of whole blood gene expression (overall 17,534 unique genes measured by microarray) and hand-grip strength in four independent cohorts (n = 7,781, ages: 20-104 yr, weighted mean = 56), adjusted for age, sex, height, weight, and leukocyte subtypes. Separate analyses were performed in subsets (older/younger than 60, men/women). Expression levels of 221 genes were associated with strength after adjustment for cofactors and for multiple statistical testing, including ALAS2 (rate-limiting enzyme in heme synthesis), PRF1 (perforin, a cytotoxic protein associated with inflammation), IGF1R, and IGF2BP2 (both insulin like growth factor related). We identified statistical enrichment for hemoglobin biosynthesis, innate immune activation, and the stress response. Ten genes were associated only in younger individuals, four in men only and one in women only. For example, PIK3R2 (a negative regulator of PI3K/AKT growth pathway) was negatively associated with muscle strength in younger (<60 yr) individuals but not older (≥ 60 yr). We also show that 115 genes (52%) have not previously been linked to muscle in NCBI PubMed abstracts. This first large-scale transcriptome study of muscle strength in human adults confirmed associations with known pathways and provides new evidence for over half of the genes identified. There may be age- and sex-specific gene expression signatures in blood for muscle strength.

Genomics and successful aging: grounds for renewed optimism?

BACKGROUND: Successful aging depends in part on delaying age-related disease onsets until later in life. Conditions including coronary artery disease, Alzheimer's disease, prostate cancer, and type 2 diabetes are moderately heritable. Genome-wide association studies have identified many risk associated single-nucleotide polymorphisms for these conditions, but much heritability remains unaccounted for. Nevertheless, a great deal is being learned. METHODS: Here, we review age-related disease associated single-nucleotide polymorphisms and identify key underlying pathways including lipid handling, specific immune processes, early tissue development, and cell cycle control. RESULTS: Most age-related disease associated single-nucleotide polymorphisms do not affect coding regions of genes or protein makeup but instead influence regulation of gene expression. Recent evidence indicates that evolution of gene regulatory sites is fundamental to interspecies differences. Animal models relevant to human aging may therefore need to focus more on gene regulation rather than testing major disruptions to fundamental pathway genes. Recent larger scale human studies of in vivo genome-wide expression (notably from the InCHIANTI aging study) have identified changes in splicing, the "fine tuning" of protein sequences, as a potentially important factor in decline of cellular function with age. Studies of expression with muscle strength and cognition have shown striking concordance with certain mice models of muscle repair and beta-amyloid phagocytosis respectively. CONCLUSIONS: The emerging clearer picture of the genetic architecture of age-related diseases in humans is providing new insights into the underlying pathophysiological pathways involved. Translation of genomics into new approaches to prevention, tests and treatments to extend successful aging is therefore likely in the coming decades.