Increased familial risk and genomewide significant linkage for Alzheimer's disease with psychosis

Psychotic symptoms are common in Alzheimer's disease (AD) and are associated with increased cognitive impairment and earlier institutionalization. One study has suggested that they are genetically modified and two genome screens have been performed to search for susceptibility loci for AD with psychosis (AD + P). The aim of this study was to further investigate the familial aggregation of AD + P and perform a genome screen for AD, conditioning on the presence or absence of psychotic symptoms. Samples from the UK and US were combined, providing data from 374 families in which at least two members met criteria for AD and had complete data regarding psychotic symptoms. Generalized estimating equations (GEE) were used to assess the relationship of psychotic symptoms between siblings. A total of 321 affected relative pairs (ARPs) were genotyped for linkage. There was a significant association between proband psychosis status and the occurrence of AD + P in siblings in the UK (OR = 4.17, P = 0.002) and US (OR = 3.2, P < 0.001) samples. Chromosomewide and genomewide significant linkage peaks were observed on chromosomes 7 (LOD = 2.84) and 15 (LOD = 3.16), respectively, with the strongest evidence coming from pairs concordant for AD without psychosis. A LOD score of 2.98 was observed close to a previously reported AD + P linkage region on chromosome 6, however the increase in LOD attributable to psychosis was not significant. These findings support the hypothesis that psychotic symptoms in AD are genetically modified and that a gene/s implicated in their aetiology may be located on chromosome 7 and 15.

Delay in access to appropriate care for children presenting with musculoskeletal symptoms and ultimately diagnosed with juvenile idiopathic arthritis

OBJECTIVE

To document pathways of care, management, and interval from onset of symptoms to first pediatric rheumatology multidisciplinary team (PRhMDT) assessment for children with incident juvenile idiopathic arthritis (JIA).

METHODS

We conducted a retrospective observational study of children with incident JIA over a 3-year period.

RESULTS

The study included 152 patients with JIA (87 females). The median interval from symptom onset to first PRhMDT assessment was 20 weeks (range 0-416), with significant variation between JIA subtypes (P = 0.0097); children with extended oligoarticular JIA had the longest interval (median 60 weeks, range 12-320). Prior to pediatric rheumatology assessment, many children had referrals to multiple secondary care specialties and had been subjected to multiple and often invasive procedures including arthroscopy/synovial biopsy (18 [11.8%] of 152), but none were referred for ophthalmologic screening, physical therapy, or nursing input and a diagnosis of JIA was rarely made (98%). At first PRhMDT assessment, most patients had untreated active disease with active joint count >or=1 (135 [89%] of 152), restricted joint count >or=1 (135 [89%] of 152), and functional disability by Child Health Assessment Questionnaire score >0 (53 [68%] of 118); 1 child had undetected uveitis. Following PRhMDT assessment, interventions were invariably indicated, including joint injections (69 [45%] of 152), methotrexate (49 [32%] of 152), and physical therapy programs (all patients).

CONCLUSION

Delay in access to pediatric rheumatology assessment is common with complex pathways of referral. Many children were subjected to inappropriate invasive investigations and many had prolonged untreated active disease at the initial PRhMDT assessment. This delay is likely to affect long-term outcome and warrants further exploration.

Genome-wide linkage analysis of 723 affected relative pairs with late-onset Alzheimer's disease

Previous attempts to identify genetic loci conferring risk for late-onset Alzheimer's disease (LOAD) through linkage analysis have observed some regions of linkage in common. However, due to the sometimes-considerable overlap between the samples, some of these reports cannot be considered to be independent replications. In order to assess the strength of the evidence for linkage and to obtain the best indication of the location of susceptibility genes, we have amalgamated three large samples to give a total of 723 affected relative pairs (ARPs). Multipoint, model-free ARP linkage analysis was performed. Genome-wide significant evidence for linkage was observed on 10q21.2 (LOD=3.3) and genome-wide suggestive evidence was observed on 9q22.33 (LOD=2.5) and 19q13.32 (LOD=2.0). One further region on 9p21.3 was identified with an LOD score>1. We observe no evidence to suggest that more than one locus is responsible for the linkage to 10q21.2, although this linked region may harbour more than one susceptibility gene. Evidence of allele-sharing heterogeneity between the original collection sites was observed on chromosome 9 but not on chromosome 10 or 19. Evidence for an interaction was observed between loci on chromosomes 10 and 19. Where samples overlapped, the genotyping consistency was high, estimated to average at 97.3%. Our large-scale linkage analysis consolidates clear evidence for a susceptibility locus for LOAD on 10q21.2.

The frequency and impact of restless legs syndrome in primary care

This study examined the prevalence and impact of moderate to severe RLS (MS-RLS) in primary care patients in Ireland. Patients completed a screening questionnaire and those with symptoms suggestive of MS-RLS underwent a diagnostic interview. Patients diagnosed with MS-RLS completed quality of life and sleep assessment questionnaires, and their medical records were examined. Of 2628 patients screened for RLS, 74 (2.8%, 95% confidence interval 2.2%-3.5%) were ultimately diagnosed at interview as having MS-RLS. These patients reported significant impact on sleep and quality of life; 24 (32.4%) had consulted a health care professional about their RLS symptoms but only 4 (16.7%) were diagnosed with RLS. Ten (13.5%) MS-RLS patients were taking inappropriate medicines to try to relieve their symptoms. Clinically significant RLS is common in Irish general practice and has a significant effect on sleep and quality of life. Nevertheless, the condition often goes undiagnosed.

Common genetic variation within the low-density lipoprotein receptor-related protein 6 and late-onset Alzheimer's disease

Genome-wide linkage studies have defined a broad susceptibility region for late-onset Alzheimer's disease on chromosome 12, which contains the Low-Density Lipoprotein Receptor-Related Protein 6 (LRP6) gene, a coreceptor for Wnt signaling. Here, we report the association between common LRP6 variants and late-onset Alzheimer's disease in a multicenter case-control series as well as in a large family-based series ascertained by the National Institute of Mental Health-National Institute on Aging Genetics Initiative. As shown in the genome-wide linkage studies, our association depends mainly on apolipoprotein E-epsilon4 (APOE-epsilon4) carrier status. Haplotype tagging single-nucleotide polymorphisms (SNPs) with a set of seven allelic variants of LRP6 identified a putative risk haplotype, which includes a highly conserved coding sequence SNP: Ile-1062 --> Val. Functional analyses revealed that the associated allele Val-1062, an allele previously linked to low bone mass, has decreased beta-catenin signaling in HEK293T cells. Our study unveils a genetic relationship between LRP6 and APOE and supports the hypothesis that altered Wnt/beta-catenin signaling may be involved in this neurodegenerative disease.

Insulin-degrading enzyme haplotypes affect insulin levels but not dementia risk

BACKGROUND

Insulin-degrading enzyme (IDE) polymorphism is hypothesized to regulate insulin levels as well as processes involved in neuronal compromise found in dementia.

METHODS

We examined the association of IDE haplotypes with dementia and insulin levels in a single well-characterized cohort of Japanese-American men born between 1900 and 1919 and followed since 1965. In 1991, a fasting insulin was obtained; dementia cases were ascertained in 1991 and 1994 in a multi-stage procedure, diagnoses were made according to international guidelines. Five single-nucleotide polymorphisms were genotyped and used for haplotype analysis in a sample of 179 Alzheimer's disease cases, 104 vascular dementia cases and 516 controls nested in the total cohort.

RESULTS

The global test for the haplotype effect on insulin levels was significant (p < 0.0001), adjusting for age, education, apolipoprotein epsilon4 status and fasting glucose.

CONCLUSION

There was no association of IDE haplotypes with the risk of dementia. This study suggests IDE may be indirectly related to dementia via its regulation of insulin levels, but it is not a major gene for Alzheimer's.

Musculoskeletal screening examination (pGALS) for school-age children based on the adult GALS screen

OBJECTIVE

To develop and validate a musculoskeletal screening examination applicable to school-age children based on the adult Gait, Arms, Legs, Spine (GALS) screen.

METHODS

Adult GALS was tested in consecutive school-age children attending pediatric rheumatology clinics and was compared with an examination conducted, on the same day, by a pediatric rheumatologist who classified children as having abnormal or normal joints. Adult GALS was tested for validity compared with the pediatric rheumatologist's assessment and deficiencies in adult GALS were identified. Experts proposed amendments to adult GALS, achieving consensus by modified Delphi techniques. The resultant pediatric screening tool (pGALS) was tested (methodology identical to the testing of adult GALS) in an additional group of children.

RESULTS

Adult GALS was tested in 50 children (median age 11 years, range 4-16), of whom 37 (74%) had juvenile idiopathic arthritis. Adult GALS missed important abnormalities in 18% of children, mostly at the ankle, foot, and temporomandibular joints. The pGALS was tested in 65 children (median age 13 years, range 5-17 years) and demonstrated excellent sensitivity (97-100%) and specificity (98-100%) at all joints, with high acceptability scored by child and parent/guardian. The median time to perform pGALS was 2 minutes (range 1.5-3 minutes).

CONCLUSION

The pGALS musculoskeletal screening tool has excellent validity, is quick to perform, and is acceptable to school-age children and parents/guardians. We propose that pGALS be incorporated into undergraduate and postgraduate medical training to improve pediatric musculoskeletal clinical skills and facilitate diagnosis and referral to specialists.

Interleukin-6 signalling in juvenile idiopathic arthritis is limited by proteolytically cleaved soluble interleukin-6 receptor

OBJECTIVES

Interleukin-6 (IL-6) exerts multiple effects on chondrocytes and fibroblasts within the joint and is associated with disease activity in juvenile idiopathic arthritis (JIA). Although these cells express the ubiquitous signalling receptor for all IL-6-related cytokines, gp130, they do not express a cognate IL-6 receptor. Consequently, IL-6 responses within these cells occur via IL-6 trans-signalling relying on the presence of a soluble receptor (sIL-6R). Levels of sIL-6R in vivo are governed by either proteolytic cleavage (PC) of cognate receptor or by differential sIL-6R mRNA splicing (DS). The aim of this study was to evaluate the contribution of both isoforms to clinical parameters associated with IL-6 signalling in JIA.

METHODS

IL-6, sIL-6R and DS-sIL-6R were measured by ELISA in serum and synovial fluid (SF) samples from 86 JIA patients. These data were related to indicators of inflammation-erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) and compared between patients stratified by subtype, age and disease duration.

RESULTS

SF IL-6 significantly correlated with general indicators of activity (ESR and CRP) and SF PC-sIL-6R to a lesser degree with CRP. When the IL-6:sIL-6R ratio was calculated as an indicator of the potential for IL-6 signalling within the joint, 33% of SF samples showed a ratio >1 indicating saturation of sIL-6R by IL-6. Mean DS-sIL-6R levels were 0.71 ng/ml, whereas PC-sIL-6R levels constituted the majority of sIL-6R at 20.89 ng/ml.

CONCLUSIONS

IL-6 trans-signalling within the joints of JIA patients is predominantly governed by the presence of PC-sIL-6R, and the data provided suggest that synovial levels of IL-6 and sIL-6R would be sufficient to drive IL-6 responses in chondrocytes and synovial fibroblasts.

Alteration and acquisition of Siglecs during in vitro maturation of CD34+ progenitors into human mast cells

Using human mast cells (MC) derived by culture of CD34+ peripheral blood precursors, a comprehensive study was performed of expression of 11 known Siglecs. Analysis was initially performed at the mRNA level using gene arrays. Positive results were then validated at the protein level using indirect immunofluorescence and flow cytometry, and for some Siglecs, Western blot analysis was also used. Culture-derived MC expressed mRNA for CD22 (Siglec-2), CD33 (Siglec-3), Siglec-5, Siglec-6, Siglec-8 and Siglec-10. Flow cytometry confirmed surface expression of all these molecules except for CD22 and Siglec-10, where levels were low or undetectable. However, Western blotting was able to detect MC expression of CD22 and Siglec-10, suggesting that these proteins were mostly cytoplasmic. CD34+ precursor cells from peripheral blood constitutively expressed surface CD33, Siglec-5 and Siglec-10. As they matured into MC, their constitutive levels of CD33 changed little, Siglec-5 and Siglec-10 declined, and Siglec-6 and Siglec-8 appeared de novo, all in parallel with accumulation of histamine and other MC markers, such as surface expression of FcepsilonRIalpha, and CD51. Phenotypic analysis of LAD-2 MC yielded a similar pattern of Siglec expression except that CD22 expression was particularly prominent. Finally, immunohistochemistry confirmed expression of these same Siglecs by mature tryptase-positive MC in human lung tissues. These data demonstrate an extensive and previously unappreciated pattern of Siglec expression on human MC. Whether engagement and signaling through these inhibitory Siglecs can impact MC biology will require further investigation.

A scan of chromosome 10 identifies a novel locus showing strong association with late-onset Alzheimer disease

Strong evidence of linkage to late-onset Alzheimer disease (LOAD) has been observed on chromosome 10, which implicates a wide region and at least one disease-susceptibility locus. Although significant associations with several biological candidate genes on chromosome 10 have been reported, these findings have not been consistently replicated, and they remain controversial. We performed a chromosome 10-specific association study with 1,412 gene-based single-nucleotide polymorphisms (SNPs), to identify susceptibility genes for developing LOAD. The scan included SNPs in 677 of 1,270 known or predicted genes; each gene contained one or more markers, about half (48%) of which represented putative functional mutations. In general, the initial testing was performed in a white case-control sample from the St. Louis area, with 419 LOAD cases and 377 age-matched controls. Markers that showed significant association in the exploratory analysis were followed up in several other white case-control sample sets to confirm the initial association. Of the 1,397 markers tested in the exploratory sample, 69 reached significance (P < .05). Five of these markers replicated at P < .05 in the validation sample sets. One marker, rs498055, located in a gene homologous to RPS3A (LOC439999), was significantly associated with Alzheimer disease in four of six case-control series, with an allelic P value of .0001 for a meta-analysis of all six samples. One of the case-control samples with significant association to rs498055 was derived from the linkage sample (P = .0165). These results indicate that variants in the RPS3A homologue are associated with LOAD and implicate this gene, adjacent genes, or other functional variants (e.g., noncoding RNAs) in the pathogenesis of this disorder.

Tangle Diseases and the Tau Haplotypes

Neurofibrillary tangles are found in many neurologic diseases. Here we review the unusual characteristics of the MAPT locus, which shows genetic association with many of these diseases and in Caucasian populations, is the largest stretch of linkage disequilibrium in the genome. We discuss the reason for this disequilibrium, its evolutionary history, and the role of genetic variability at MAPT in the etiology of tauopathies.

Evidence suggesting that Homo neanderthalensis contributed the H2 MAPT haplotype to Homo sapiens

The tau (MAPT) locus exists as two distinct clades, H1 and H2. The H1 clade has a normal linkage disequilibrium structure and is the only haplotype found in all populations except those derived from Caucasians. The H2 haplotype is the minor haplotype in Caucasian populations and is not found in other populations. It shows no recombination over a region of 2 Mb with the more common H1 haplotype. The distribution of the haplotype and analysis of the slippage of dinucleotide repeat markers within the haplotype suggest that it entered Homo sapiens populations between approx. 10000 and 30000 years ago. However, sequence comparison of the H2 haplotype with the H1 haplotype and with the chimp sequence suggests that the common founder of the H1 and H2 haplotypes was far earlier than this. We suggest that the H2 haplotype is derived from Homo neanderthalensis and entered H. sapiens populations during the co-existence of these species in Europe from approx. 45000 to 18000 years ago and that the H2 haplotype has been under selection pressure since that time, possibly because of the role of this H1 haplotype in neurodegenerative disease.

Levels of matrix metalloproteinase (MMP)-1 in paired sera and synovial fluids of juvenile idiopathic arthritis patients: relationship to inflammatory activity, MMP-3 and tissue inhibitor of metalloproteinases-1 in a longitudinal study

OBJECTIVES

To measure levels of the collagenases matrix metalloproteinase (MMP)-1 and -13 in the synovial fluid (SF) and serum of patients with juvenile idiopathic arthritis (JIA), and to correlate these measurements with inflammatory activity, levels of the collagenase activator MMP-3 and the tissue inhibitor of metalloproteinases-1 (TIMP-1).

METHODS

Levels of MMP-1, -3, -13 and TIMP-1 were measured in paired SF and serum from 82 JIA patients using enzyme-linked immunsorbent assay and compared between subtypes and patients of different ages and disease durations. These levels were also correlated to the active joint count (AJC) and standard measures of inflammatory activity and therapeutic response, including erythrocyte sedimentation rate (ESR) and platelet count (PLT).

RESULTS

MMP-1 was detected in JIA SF and correlated with PLT. MMP-3 levels were high in SF and detectable in serum where they correlated with PLT, ESR and AJC. MMP-13, however, was not detected in SF or serum. No differences were observed between patients grouped by subtype, age or disease duration. MMP-3 contributed the majority of total MMP in SF samples resulting in excess MMP levels over TIMP-1.

CONCLUSIONS

MMP-1 is up-regulated in SF concordant with inflammatory activity in JIA. This was true for patients in all JIA subtypes and age groups, suggesting that the capability for degradation of type II collagen is present in early disease, and throughout the disease course. MMP-3 may be important in the activation of collagenases and the saturation of exogenous inhibitors. Serum MMP-3 may therefore be a useful, measurable and specific marker of active disease in JIA.

Vector projection of biomagnetic fields

Biomagnetic measurements are increasingly popular as functional imaging techniques for the non-invasive assessment of electrically active tissue. Although most currently available magnetometers utilise only one component of the vector magnetic field, some studies have suggested the possibility of obtaining additional information from recordings of the full magnetic field vector. Three projection techniques were applied to different biomagnetic signals for analysis of the three orthogonal components of the vector magnetic field. Vector magnetic fields obtained from fetal cardiac activity were projected into evenly spaced directions around a unit sphere. The vector magnetic field recorded from multiple intestinal current sources with independent temporal frequencies was then projected. Finally, an external reference signal from an invasive electrode was used to project the recorded vector magnetic fields due to gastric electrical activity. In each case, it was found that the information obtained by examination of the projected magnetic field vectors gave superior clinical insight to that obtained by analysis of any single magnetic field component.

Association studies between risk for late-onset Alzheimer's disease and variants in insulin degrading enzyme

Linkage studies have suggested there is a susceptibility gene for late onset Alzheimer's disease (LOAD) in a broad region of chromosome 10. A strong positional and biological candidate is the gene encoding the insulin-degrading enzyme (IDE), a protease involved in the catabolism of Abeta. However, previous association studies have produced inconsistent results. To systematically evaluate the role of variation in IDE in the risk for LOAD, we genotyped 18 SNPs spanning a 276 kb region in and around IDE, including three "tagging" SNPs identified in an earlier study. We used four case-control series with a total of 1,217 cases and 1,257 controls. One SNP (IDE_7) showed association in two samples (P-value = 0.0066, and P = 0.026, respectively), but this result was not replicated in the other two series. None of the other SNPs showed association with LOAD in any of the tested samples. Haplotypes, constructed from the three tagging SNPs, showed no globally significant association. In the UK2 series, the CTA haplotype was over-represented in cases (P = 0.046), and in the combined data set, the CCG haplotype was more frequent in controls (P = 0.015). However, these weak associations observed in our series were in the opposite direction to the results in previous studies. Although our results are not universally negative, we were unable to replicate the results of previous studies and conclude that common variants or haplotypes of these variants in IDE are not major risk factors for LOAD.

Genome screen for loci influencing age at onset and rate of decline in late onset Alzheimer's disease

We performed an affected sib-pair (ASP) linkage analysis to test for the effects of age at onset (AAO), rate of decline (ROD), and Apolipoprotein E (APOE) genotype on linkage to late-onset Alzheimer's disease (AD) in a sample comprising 428 sib-pairs. We observed linkage of mean AAO to chromosome 21 in the whole sample (max LOD = 2.57). This came entirely from the NIMH sample (max LOD = 3.62), and was strongest in pairs with high mean AAO (>80). A similar effect was observed on chromosome 2q in the NIMH sample (max LOD = 2.73); this region was not typed in the IADC/UK sample. Suggestive evidence was observed in the combined sample of linkage of AAO difference to chromosome 19q (max LOD = 2.33) in the vicinity of APOE and 12p (max LOD = 2.22), with linkage strongest in sib-pairs with similar AAO. Mean ROD showed suggestive evidence of linkage to chromosome 9q in the whole sample (max LOD = 2.29), with the effect strongest in the NIMH sample (max LOD = 3.58), and in pairs with high mean ROD. Additional suggestive evidence was also observed in the NIMH sample with AAO difference on chromosome 6p (max LOD = 2.44) and 15p (max LOD = 1.87), with linkage strongest in pairs with similar AAO, and in the UK sample with mean ROD on chromosome 1p (max LOD = 2.73, linkage strongest in pairs with high mean ROD). We also observed suggestive evidence of increased identical by descent (IBD) in APOE epsilon4 homozygotes on chromosome 1 (max LOD = 3.08) and chromosome 9 (max LOD = 3.34). The previously reported genome-wide linkage of AD to chromosome 10 was not influenced by any of the covariates studied.

Recurrence risk for psoriasis and psoriatic arthritis within sibships

OBJECTIVE

To quantify the frequency of siblings of patients with psoriatic arthritis (PsA) having psoriasis and/or inflammatory arthritis. To describe the similarity or otherwise of patterns of arthritis in siblings.

METHODS

Available and consenting index cases with PsA and one or more siblings living locally were assessed. Mean sibling concordance rates and Weinberg's segregation analysis were calculated. Heritability was also estimated. To assess whether the same type of arthritis occurred within the same sibship, the dually affected sibships were then classified for type of arthritis according to methods suggested by Moll, Helliwell, Veale and McGonagle.

RESULTS

Eighty index cases and 112 siblings were assessed. The median age of index cases was 49 yr (range 24-80 yr) and for siblings 46 yr (range 18-79 yr). The concordance rate for all types of PsA was 14% (9% if enthesitis is excluded) and for psoriasis 21%. There was no difference in the two methods used to calculate concordance rates. Sixteen dually affected sib pairs were found. Four of the 16 sibships (25%) had the same pattern of joint involvement (Moll and Wright classification). The most frequent pattern seen was joint involvement identical to rheumatoid arthritis (3/5). The most common symptom in affected siblings was enthesitis (approximately 5%). When the dually affected sibships were analysed using the other classifications, the simpler the classification the greater the concordance for joint pattern.

CONCLUSION

The concordance for psoriasis is greater than for PsA, but the concordance rate for PsA was similar to that in HLA identical siblings with rheumatoid arthritis. There was discordance in pattern of arthritis for most sib pairs. There is no support for the use of more complex classifications of PsA.