Association study of the GAB2 gene with the risk of developing Alzheimer's disease.

The first genome-wide association in Alzheimer's disease (AD) suggested that the GAB2 gene rs2373115 polymorphism may be a strong risk factor in APOE varepsilon4-carriers. We failed to detect an association of rs2373115 with the risk of developing AD in three populations (totalling 1406 controls and 1749 AD cases) whatever the APOE status, even if we observed a slight tendency for an increase of the GG genotype (OR (GG versus GT+TT)=1.3, 95% CI 1.0-1.6, p=0.09) and the G allele frequency (OR=1.3, 95%CI 1.0-1.6, p=0.05) in varepsilon4-carriers. In addition, the rs2373115 did not modulate the extent of tau phosphorylation in the brain of 89 AD cases. The GAB2 gene is at best a minor genetic determinant of AD.

Association study of the Ubiquilin gene with Alzheimer's disease.

Recently, the ubiquilin 1 gene has been proposed as a major candidate gene for AD. Here, we have investigated the potential impact of the UBQ-8i polymorphism (rs12344615) within this gene on the risk of developing AD. No association of this polymorphism with the disease was observed in a large French case-control population. Furthermore, no relationship between this polymorphism and Abeta load or degree of neurofibrillary degeneration in the brains of 114 patients with AD was detected.

Association study and meta-analysis of low-density lipoprotein receptor related protein in Alzheimer's disease.

Genome scans in sporadic Alzheimer's disease (AD) have revealed a possible susceptibility locus on chromosome 12. The low density lipoprotein receptor related protein (LRP1) gene lies within this area of linkage. Eighteen previous AD case-control studies have investigated the C766T polymorphism in LRP1 with conflicting results, including a protective effect on AD of the T allele, an increased susceptibility towards AD with both the C and T alleles, or no association at all. We have now performed a case-control study based on a large UK cohort of 477 AD patients and 466 matched controls, and have included these data, with those drawn from the 18 previous studies, into in a meta-analysis of 4668 AD patients and 4473 controls. We find no evidence for influence on the risk for AD in either our own present cohort or in the combined data set. Furthermore, we investigated whether the C766T polymorphism might modify the clinical and pathological phenotype in our cohort. We found no association with AD when the cohort was stratified into those with early (<65 years) or late (>65 years) onset, or when split into Apolipoprotein E (APOE) epsilon4 bearers and epsilon4 non-bearers. In addition, the C766T polymorphism was shown not to influence the age onset of AD. In a separate autopsy-confirmed cohort of 130 AD cases, no association with genotype or allele was observed for tissue levels of beta-amyloid 40, beta-amyloid 42, total beta-amyloid, pathological tau proteins, microglial cells or extent of astrocytic activity. Therefore, in this present study, we find no evidence for the involvement of this polymorphism either in increasing the susceptibility to AD, or by acting as a phenotypic modifier.

Ephrin-As play a rhombomere-specific role in trigeminal motor axon projections in the chick embryo.

In this study, we investigate the possible role of ephrin-Eph signaling in trigeminal motor axon projections. We find that EphA receptors are expressed at higher levels by rhombomere 2 (r2) trigeminal motor neurons than by r3 trigeminal motor neurons in the chick embryo. Mapping of rhombomere-specific axon projections shows that r2 and r3 trigeminal motor neurons project to different muscle targets, including the mandibular adductor and the intermandibularis muscles respectively. Ephrin-A5 is expressed in these muscles, especially in some regions of the intermandibularis muscle, and can cause growth cone collapse of both r2 and r3 motor axons in vitro. We demonstrate that in vivo overexpression of ephrin-A5 in the intermandibularis muscle, or overexpression of dominant-negative EphA receptors in trigeminal motor neurons leads to a reduction in branching of r3-derived motor axons specifically. Overexpression of full-length EphA receptors impairs the formation of r3 projections to the intermandibularis muscle. These findings indicate that ephrins and their Eph receptors play a role in trigeminal motor axon topographic mapping and in rhombomere 3-derived projections in particular.

Interleukin-6 promoter polymorphism: risk and pathology of Alzheimer's disease.

Inflammatory and immune responses are involved in the pathogenesis of Alzheimer's disease (AD). Interleukin-6 (IL-6), an inflammatory cytokine, is thought to play a role in neurodegeneration of the central nervous system and has been associated with increased amyloid precursor protein expression in vitro and greater cognitive decline. Previously a C-174G polymorphism in the promoter of IL-6, which influences expression in vitro, has been found associated in some studies but not all. We investigated this polymorphism in a large independent UK sample of AD cases (n = 356) and controls (n 434) but found no association. We extended the study to genotype/phenotype correlations but found no correlation with age of onset (n = 338), brain amyloid load (n = 126) or Tau load (n = 101), brain microglial cell load (n = 65) or brain reactive astrocytes (n = 127). Our data do not support a pathogenic role in AD for the C-174G polymorphism in isolation.