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.

Genetic contributions to variation in general cognitive function: a meta-analysis of genome-wide association studies in the CHARGE consortium (N=53949)

General cognitive function is substantially heritable across the human life course from adolescence to old age. We investigated the genetic contribution to variation in this important, health- and well-being-related trait in middle-aged and older adults. We conducted a meta-analysis of genome-wide association studies of 31 cohorts (N=53,949) in which the participants had undertaken multiple, diverse cognitive tests. A general cognitive function phenotype was tested for, and created in each cohort by principal component analysis. We report 13 genome-wide significant single-nucleotide polymorphism (SNP) associations in three genomic regions, 6q16.1, 14q12 and 19q13.32 (best SNP and closest gene, respectively: rs10457441, P=3.93 × 10(-9), MIR2113; rs17522122, P=2.55 × 10(-8), AKAP6; rs10119, P=5.67 × 10(-9), APOE/TOMM40). We report one gene-based significant association with the HMGN1 gene located on chromosome 21 (P=1 × 10(-6)). These genes have previously been associated with neuropsychiatric phenotypes. Meta-analysis results are consistent with a polygenic model of inheritance. To estimate SNP-based heritability, the genome-wide complex trait analysis procedure was applied to two large cohorts, the Atherosclerosis Risk in Communities Study (N=6617) and the Health and Retirement Study (N=5976). The proportion of phenotypic variation accounted for by all genotyped common SNPs was 29% (s.e.=5%) and 28% (s.e.=7%), respectively. Using polygenic prediction analysis, ~1.2% of the variance in general cognitive function was predicted in the Generation Scotland cohort (N=5487; P=1.5 × 10(-17)). In hypothesis-driven tests, there was significant association between general cognitive function and four genes previously associated with Alzheimer's disease: TOMM40, APOE, ABCG1 and MEF2C.

Role of extracellular ionized calcium in the in vitro assessment of GPIIb/IIIa receptor antagonists

Several preclinical studies have found a poor correlation between the ex vivo platelet inhibitory potency and the in vivo antithrombotic efficacy of GPIIb/IIIa receptor antagonists. The present study was designed to examine the differential in vitro potencies of c7E3, MK-383, DMP-728, and SM-20302 in inhibiting ex vivo platelet aggregation under normocalcemic and hypocalcemic conditions. Human blood was collected in either trisodium citrate (0. 37%) or PPACK (20 microg/mL). Platelet aggregation assays were performed in platelet-rich plasma from citrate-anticoagulated blood (cPRP) and PPACK-anticoagulated blood (pPRP) using ADP (20 microM) and TRAP (10 microM) as agonists in the presence of c7E3, MK-383, DMP-728, or SM-20302. The concentration of ionized calcium in cPRP was 16-19 times lower than that in pPRP. The IC(50) of c7E3 for inhibiting ADP-induced platelet aggregation in cPRP (2.76 +/- 0.11 microg/mL) was 1.6 times lower than that in pPRP (4.46 +/- 0.48 microg/mL; P < 0.05). Similarly, the IC(50) for c7E3 for inhibiting TRAP-induced platelet aggregation in cPRP (4.52 +/- 0.34 microg/mL) was 1.7 times lower than that in pPRP (7.69 +/- 0.43 microg/mL; P < 0.05). MK-383, DMP-728, and SM-20302 also demonstrated 1.96-, 1.15-, and 1.43-fold lower IC(50) values, respectively, in cPRP as compared with pPRP. Chelation of ionized calcium in pPRP led to a progressive increase in platelet inhibition by all the antagonists. These results suggest that the observed in vitro inhibitory potency of a GPIIb/IIIa receptor antagonist is markedly enhanced when trisodium citrate is used as an anticoagulant to collect blood for ex vivo assay. These findings indicate that dosing regimens for GPIIb/IIIa receptor antagonists based on the platelet inhibition profile in citrate may provide misleading information with respect to their true in vivo antithrombotic efficacy.

Correlation between the in vivo efficacy of GPIIb/IIIa receptor antagonists (m7E3, MK-383 and DMP-728) and ex vivo platelet inhibition

In vivo antithrombotic efficacy of GPIIb/IIIa receptor antagonists (m7E3, MK-383 and DMP-728) was studied with respect to their ex vivo platelet inhibition in heparinized platelet-rich plasma (hPRP) and citrated platelet-rich plasma (cPRP) using a canine model of carotid artery thrombosis. For each drug group (n = 6), the right carotid artery was used as control vessel and resulting occlusive thrombus was kept in situ to examine the direct thrombolytic efficacy of the antagonists. Thirty minutes after occlusion of control vessel, a low or high dose of each antagonist was administered and the left carotid artery was used as test vessel. All control vessels occluded within 86-96 min in response to electrolytic injury. The incidence of occlusion with lower doses of m7E3, DMP-728, and MK-383 was 100, 33 and 100%, respectively; corresponding times to occlusion were 174, 220 and 118 min. Lower doses inhibited ADP- or AA-induced platelet aggregation in cPRP (>80%). Incidence of occlusion with high doses of m7E3, DMP-728 and MK-383 was 33, 0 and 0%, respectively; corresponding times to occlusion were 209, >240 and >240 min. Higher doses inhibited aggregation in cPRP (>80%), but only partially in hPRP (45-66%). Dose-dependent prolongation of bleeding time occurred with all antagonists. None of the antagonists lyzed preformed thrombi in control vessels. The results indicate that ex vivo platelet aggregation conducted in hPRP, as opposed to conventional cPRP, provides a better assessment of the in vivo efficacy of GPIIb/IIIa receptor antagonists.