Quantitative genetics of circulating Dickkopf-related protein 1 (DKK1) in community-based sample of UK twins

Quantile-Dependent Expressivity of Serum Interleukin-6 Concentrations as a Possible Explanation of Gene-Disease Interactions, Gene-Environment Interactions, and Pharmacogenetic Effects

Interleukin 6 (IL-6) is a moderately heritable pleiotropic cytokine whose elevated concentrations in coronary artery disease, peripheral arterial disease, pulmonary arterial hypertension, Eales' disease, Sjògren's syndrome, osteoarthritis, adenocarcinoma, neuroblastoma, polymyalgia rheumatica, pulmonary tuberculosis, and enterovirus 71 infection, and following coronary artery bypass graft show larger genetic effects than in unaffected low IL-6 controls. We hypothesize that genetic effects may depend upon whether average IL-6 concentrations are high or low, i.e., quantile-dependent expressivity. Quantile-specific offspring-parent (β_OP) and full-sib regression slopes (β_FS) were estimated by applying quantile regression to the age- and sex-adjusted serum IL-6 concentrations in families surveyed in the Framingham Heart Study. Quantile-specific heritabilities were calculated as h² = 2β_OP / (1 + r_spouse) and h² = {(1 + 8r_spouseβ_FS)^0.5 -1} / (2r_spouse)). Heritability (h² ± SE) of IL-6 concentrations increased from 0.01 ± 0.01 at the 10th percentile (NS), 0.02 ± 0.01 at the 25th (P = 0.009), 0.03 ± 0.01 at the 50th (P = 0.007), 0.04 ± 0.02 at the 75th (P = 0.004), and 0.13 ± 0.05 at the 90th percentile (P = 0.03), or 0.0005 ± 0.0002 for each 1% increase in the offspring's phenotype distribution (P_{linear trend} = 0.02) when estimated from β_OP and from 0.02 ± 0.02 at the 10th (NS), 0.02 ± 0.02 at the 25th (NS), 0.06 ± 0.02 at the 50th (P = 0.01), 0.12 ± 0.04 at the 75th (P = 0.001), and 0.30 ± 0.03 at the 90th percentile (P < 10^-16), or 0.0015 ± 0.0007 for each 1% increase in the sibling phenotype distribution (P_{linear trend} = 0.02) when estimated from β_FS. Thus the heritability of serum IL-6 concentrations is quantile dependent, which may contribute in part to the larger genetic effect size reported for diseases and environmental conditions that elevate IL-6 concentrations vis-à-vis unaffected controls.

Association between the group III metabotropic glutamate receptor gene polymorphisms and attention-deficit/hyperactivity disorder and functional exploration of risk loci

Existing evidence suggests that the group III metabotropic glutamate receptor (mGluR) gene variations are involved in attention-deficit/hyperactivity disorder (ADHD), but few studies have fully explored this association. We conducted a case-control study with 617 cases and 636 controls to investigate the association between functional single-nucleotide polymorphisms (SNPs) from the group III mGluR gene polymorphisms (GRM4, GRM7, GRM8) and ADHD in the Chinese Han population and initially explored the function of positive SNPs. The GRM4 rs1906953 T genotype showed a significant association with a decreased risk of ADHD (TT:CC, OR = 0.55, 95% CI = 0.40-0.77; recessive model, OR = 0.58, 95% CI = 0.43-0.78). GRM7 rs9826579 C showed a significant association with an increased risk of ADHD (TC:TT, OR = 1.81, 95% CI = 1.39-2.36; dominant model, OR = 1.74, 95% CI = 1.35-2.24; additive model, OR = 1.56, 95% CI = 1.24-1.97). In addition, compared with subjects with the rs1906953 TT genotype, subjects with of the CC genotype showed more obvious attention deficit behaviours and hyperactivity/impulsive behaviours. Dual-luciferase reporter gene assays showed that a promoter reporter with the rs1906953 TT genotype significantly decreased luciferase activity compared with the CC genotype. According to electrophoretic mobility shift assays, the binding capacity of rs1906953 T probe with nucleoprotein was lower than that of the rs1906953 C probe. Our results revealed the association of GRM4 rs1906953 and GRM7 rs9826579 with ADHD. Moreover, we found that rs1906953 disturbs the transcriptional activity of GRM4.

Dickkopf-1 Expression in Androgenetic Alopecia and Alopecia Areata in Male Patients

BACKGROUND

Androgenetic alopecia (AGA) results from shortening of the anagen phase of the hair cycle and, subsequently, miniaturization of hair follicles. Alopecia areata (AA) is a disease of autoimmunity where T cells attack anagen hair follicles and shows multifactorial etiology. Dickkopf-1 (DKK-1) is a gene that is responsible for transformation of anagen to catagen, which suggests that it is involved in development of both diseases.

OBJECTIVES

To evaluate the tissue levels of dickkopf-1 in male patients with AGA and AA in comparison with controls, in an attempt to know its role in the pathogenesis of both disorders.

METHODS

DKK-1 immunohistochemical expression was evaluated in lesional scalp biopsies taken from 20 male patients with AGA evaluated clinically by the modified Norwood-Hamilton score, 20 male patients with AA evaluated clinically by SALT score, and 20 healthy controls within the same age and sex of the studied patients.

RESULTS

A highly significant difference in DKK-1 expression between patients with AGA and healthy controls was found (P2 < 0.001). There were also significant differences in DKK-1 expression between patients with AA and healthy controls (P3 = 0.013), and between both patient groups (P1 = 0.002).

CONCLUSIONS

Both AGA and AA showed significant increase in DKK-1 immunohistochemical expression. This may enhance the idea of its possible role in the pathogenesis of AGA and AA, and being a new target for treatment of these hair disorders.

Quantitative genetics of circulating Hyaluronic Acid (HA) and its correlation with hand osteoarthritis and obesity-related phenotypes in a community-based sample

BACKGROUND

One of the potential molecular biomarkers of osteoarthritis (OA) is hyaluronic acid (HA). HA levels may be related to the severity and progression of OA. However, little is known about the contribution of major risk factors for osteoarthritis, e.g. obesity-related phenotypes and genetics to HA variation.

AIM

To clarify the quantitative effect of these factors on HA.

SUBJECTS AND METHODS

An ethnically homogeneous sample of 911 apparently healthy European-derived individuals, assessed for radiographic hand osteoarthritis (RHOA), HA, leptin, adiponectin, and several anthropometrical measures of obesity-related phenotypes was studied. Model-based quantitative genetic analysis was used to reveal genetic and shared environmental factors affecting the variation of the study's phenotypes.

RESULTS

The HA levels significantly correlated with the age, RHOA, adiponectin, obesity-related phenotypes, and the waist-to-hip ratio. The putative genetic effects contributed significantly to the variation of HA (66.2 ± 9.3%) and they were also significant factors in the variations of all the other studied phenotypes, with the heritability estimate ranging between 0.122 ± 4.4% (WHR) and 45.7 ± 2.2% (joint space narrowing).

CONCLUSIONS

This is the first study to report heritability estimates of HA variation and its correlation with obesity-related phenotypes, ADP and RHOA. However, the nature of genetic effects on HA and its correlation with other study phenotypes require further clarification.