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John Loughlin

Publications and source records attributed to John Loughlin.

At least 19 recordsLinked to original sources
PubMed2007

Extreme context specificity in differential allelic expression.

Variability in cis-regulation of gene expression has been implicated in the phenotypic manifestation of complex traits including common, multifactorial diseases. The differential expression of alleles due to polymorphism in cis-regulatory elements is common in the human genome, but there is a paucity of information about the context specificity of these control elements. In this study, we examined the differential allelic expression (DAE) of BMP5 in human mesenchymal tissues obtained from 16 donors undergoing joint replacement for treatment of osteoarthritis. We observed significant differences in BMP5 allelic output, with allelic ratios greater than 4:1 (P < 10(-20)) in the tissues of some donors. We also discovered a significant variability in allelic expression within the different tissues of donors. For 12 of our donors, we examined the allelic expression of BMP5 in two different regions of cartilage: cartilage adjacent to the site of the osteoarthritic lesion and cartilage distal from the lesion. Five of these 12 donors demonstrated highly significant differences (P < or = 10(-8)) in allelic expression between the different regions of their cartilage. Using DAE as a phenotype, we attempted to map tissue-specific cis-regulatory polymorphisms, and we identified a single nucleotide polymorphism located downstream of BMP5, which was significantly associated with DAE in some but not all of the examined tissues. These findings suggest that allelic expression can be highly context specific and that when interrogating the cis-regulatory control of a particular gene, one cannot necessarily assume that allelic expression is conserved across different tissues or even across different regions of the same tissue.

Alleles↗
PubMed2007

Sex and ethnic differences in the association of ASPN, CALM1, COL2A1, COMP, and FRZB with genetic susceptibility to osteoarthritis of the knee.

OBJECTIVE: To assess whether the association of genetic polymorphisms with osteoarthritis (OA) in other populations could be replicated in a large, multicenter, mixed-sex, case-control study of clinical knee OA. METHODS: Genetic polymorphisms in OA candidate genes were genotyped in 298 men and 305 women, ages 50-86 years, all of whom had a diagnosis of knee OA as assessed clinically and radiographically, and in 300 male and 299 female control subjects matched for age and ethnicity. Allele and haplotype frequencies for 5 genes (ASPN, CALM1, COL2A1, COMP, and FRZB) previously tested for association with hip and/or knee OA in other populations were compared between patients and control subjects, analyzing men and women separately. RESULTS: The same FRZB 2-marker single-nucleotide polymorphism (SNP) haplotype associated with hip OA in other populations of Caucasian women was shown to increase the risk of knee OA among the women (but not the men) in the current study (odds ratio [OR] 2.87, P < 0.04). The CALM1 SNP, which affects the risk of hip OA in Japanese individuals, was not shown to be associated with susceptibility to OA in men or women. COL2A1 haplotypes were demonstrated to be associated with a decreased risk of knee OA in men (OR 0.68, P < 0.005) but not in women. COMP haplotypes that were associated with susceptibility to knee OA were different in men and women (P < 0.014 and P < 0.032, respectively). A meta-analysis of these data and those from previously published reports indicated a strong association between the FRZB G324 allele (P < 0.0003) and suggested that an ASPN allele is protective against the risk of knee OA in Caucasians (P < 0.02). CONCLUSION: Our results indicate that genetic polymorphisms affecting knee OA vary between populations (Japanese versus Caucasian) and sexes and indicate a role for ASPN, COMP, FRZB, and COL2A1 in Caucasians.

Aged↗
PubMed2006

Reproducible genetic associations between candidate genes and clinical knee osteoarthritis in men and women.

OBJECTIVE: Osteoarthritis (OA) is recognized to have a genetic component, and in this study, we aimed to replicate in a case-control study of men and women with clinical knee OA genetic associations in 12 candidate genes previously reported to be associated with OA. METHODS: Twenty-five single-nucleotide polymorphisms were genotyped in 298 men and 305 women ages 50-86 who were diagnosed as having knee OA, as assessed both clinically and radiographically, and in 297 men and 299 women matched for age and ethnicity (controls). Standardized anteroposterior radiographs of the knee in extension were performed on each of the cases, and all cases met the American College of Rheumatology criteria for OA of the knee. Genotype and haplotype frequencies in cases and controls were compared separately in men and women. The 12 genes tested were AACT, ADAM12, BMP2, CD36, CILP, COX2, ESR1, NCOR2, OPG, TNA, TNFAIP6, and VDR. RESULTS: Eight of the candidate genes were associated in women and 5 in men, and only 3 genes (TNFAIP6, NCOR2, and CD36) were not significantly associated in either sex. The strongest associations in terms of odds ratios (ORs) were a haplotype in ADAM12 (OR 7.1 [95% confidence interval (95% CI) 3.3-33.8]) and a haplotype in ESR1 (OR 3.6 [95% CI 1.18-10.98]) in women. The same ADAM12 haplotype (OR 2.54 [95% CI 1.2-5.4]) and a haplotype in the CILP gene (OR 0.38 [95% CI 0.23-0.62]) were the strongest associations in men. CONCLUSION: We found that genes previously identified by their association with subclinical features of knee OA or progression were also associated with clinical knee OA. These genetic associations may identify individuals at a particularly high risk of developing knee OA.

Aged↗
PubMed2005

Crystals in hand.

A genetic association of the ENPP1 gene with primary hand osteoarthritis was recently reported in this journal. ENPP1 encodes an enzyme that regulates soft tissue calcification. The study as it stands is far from complete because the actual causal variant(s) within ENPP1 has not been identified and no functional study on the activity of the enzyme in hand osteoarthritis was presented. Nevertheless, the study stimulates interest and will encourage others in the field to test ENPP1 as a possible osteoarthritis susceptibility gene in their cohorts. The genetic basis of osteoarthritis is slowly being uncovered, and this report constitutes another interesting find.

Adult↗
PubMed2005

The genetic epidemiology of human primary osteoarthritis: current status.

Osteoarthritis (OA) is a common disease characterised by the degeneration of the cartilage of synovial joints such as the hip and knee. In the past ten years a large number of twin-pair, sibling-risk and segregation studies have been conducted on the disease, and these have revealed a major genetic component that is transmitted in a nonmendelian manner. OA therefore fits best into the complex, multifactorial class of common diseases. With a genetic component established, genome-wide linkage scans were performed, and these uncovered several genomic intervals likely to harbour OA susceptibility. In the past few years these intervals have started to yield genes containing OA-associated variants. This is therefore a very exciting period in the molecular genetic analysis of this common disease. The genes that have so far been implicated in susceptibility include the interleukin 1 gene (IL1) cluster at chromosome 2q11.2-q13, the matrilin 3 gene (MATN3) at 2p24.1, the IL-4 receptor alpha-chain gene (IL4R) at 16p12.1, the secreted frizzled-related protein 3 gene (FRZB) at 2q32.1, the metalloproteinase gene ADAM12 at 10q26.2 and, most recently, the asporin gene (ASPN) at 9q22.31. The evidence for involvement of these genes in OA is more compelling for some than others, with the IL1 and ASPN associations being the most convincing to date. It is imperative that the veracity of each of the associations be tested by genotyping additional cohorts and that their global relevance be assessed by genotyping OA cohorts from different ethnic backgrounds. The gene products of IL1, IL4R, FRZB and ASPN regulate cartilage chondrocyte differentiation and survival, and their effects on the chondrocyte are potentially amenable to therapeutic intervention. The latest genetics is therefore providing new insights for the development of novel OA treatments.

Cell Differentiation↗
PubMed2005

Investigating the aspartic acid (D) repeat of asporin as a risk factor for osteoarthritis in a UK Caucasian population.

OBJECTIVE: A compelling genetic association with osteoarthritis (OA) of 2 functional alleles in the aspartic acid (D) repeat of the asporin gene was recently reported in a Japanese population. Allele D13 of the repeat encoded OA protection, whereas allele D14 encoded OA susceptibility. The 2 alleles mediate differences in the capacity of asporin to inhibit the cartilage growth factor transforming growth factor beta, with the D14 allele being a particularly potent inhibitor. Our objective was to assess whether the D repeat is associated with OA in UK Caucasians. METHODS: The repeat was genotyped in 1,247 patients who had undergone elective joint replacement of the hip or the knee due to end-stage primary OA and in 748 age-matched controls. RESULTS: The D13 allele was more common in controls, and the D14 allele was more common in patients. However, this trend was significant only for men who had undergone hip replacement (P = 0.016, odds ratio 1.48, 95% confidence interval 1.09-2.01). CONCLUSION: Our data suggest that the asporin polymorphism is not a major influence on OA etiology in Caucasians. The results of our study do not question the veracity of the Japanese report. Instead, our study highlights the complex, heterogeneous nature of OA genetic susceptibility.

Aged↗
PubMed2005

Recent advances in the genetic investigation of osteoarthritis.

Osteoarthritis (OA) demonstrates considerable clinical heterogeneity, generating heated debate over whether OA is a single disease or a complex mix of disparate diseases and concerning which tissues are principally involved in disease initiation and progression. Epidemiological studies have demonstrated a major genetic component to OA risk. However, these studies have also revealed differences in risk between males and females and for disease at different skeletal sites. This observation has resulted in the concept of genes for specific sites rather than a generalised OA phenotype. Recent breakthroughs have shed considerable light on the nature of OA genetic susceptibility. Many candidate genes have been confirmed, such as the interleukin-1 gene cluster and the oestrogen alpha-receptor gene ESR1. Genome-wide linkage scans have revealed several regions harbouring novel loci, some of which are beginning to yield their genes.

Chromosome Mapping↗
PubMed2005

Genetic background increases the risk of hip osteoarthritis.

Using a cohort of 49 families with at least one affected female sibling pair who had total hip arthroplasty for end-stage primary osteoarthritis, we determined the prevalence and relative risk of symptomatic and radiographic osteoarthritis in 145 children. The relative risk of symptomatic radiographic osteoarthritis in these 145 offspring was 3.5 times greater than in 119 age-matched controls (95% confidence interval; range, 2.0-6.2). Most symptoms and radiographic changes involved the hip. Results of this study showed vertical transmission of primary osteoarthritis and that genetic influences play a major role in osteoarthritis of the hip in the Caucasian population.

Arthroplasty, Replacement, Hip↗
PubMed2005

Polymorphism in signal transduction is a major route through which osteoarthritis susceptibility is acting.

PURPOSE OF REVIEW: In the last year there has been considerable success in the identification of genes harbouring susceptibility for primary osteoarthritis. This report brings the reader up-to-date by focusing on three of the more compelling finds. RECENT FINDINGS: A UK group reported an association of the FRZB gene with hip osteoarthritis in females. FRZB codes for secreted frizzled-related protein 3, an antagonist of Wnt signalling. The Wnt signal transduction pathway is critical for normal development and is also active in adult tissues. Secreted frizzled-related protein 3 helps to maintain articular cartilage and the associated alleles at FRZB reduce the activity of this important protein. A Japanese group has reported an association of the asporin gene ASPN with knee and hip osteoarthritis and an association of the calmodulin 1 gene CALM1 with hip osteoarthritis. Asporin is a cartilage extracellular protein that regulates the activity of transforming growth factor-beta. Calmodulin is an intracellular protein that interacts with a number of proteins involved in signal transduction. The associated alleles at ASPN and CALM1 reduce the ability of chondrocytes to express the genes encoding aggrecan and type II collagen. Since these are essential structural components of articular cartilage, the ASPN and CALM1 associations are predicted to adversely affect the maintenance of cartilage. SUMMARY: The FRZB, ASPN and CALM1 results are compelling and highlight that polymorphism in signal transduction pathways is a major component of osteoarthritis susceptibility. This is an exciting observation since signal transduction pathways are malleable and therefore potentially amenable to intervention and modification.

Calmodulin↗
PubMed2004

Functional variants within the secreted frizzled-related protein 3 gene are associated with hip osteoarthritis in females.

Osteoarthritis (OA) is a leading cause of disability in Western society with multiple risk factors, including a complex genetic pattern. Identifying loci involved in the heredity of OA might lead to insights into the molecular pathogenesis of this common disorder. A previous genome scan mapped a primary hip OA susceptibility locus to chromosome 2q with a maximum multipoint logarithm of odds score of 1.6 in 378 affected sibling pair families. Here, microsatellite targeting of eight candidate genes in this region from 2q23-2q32 demonstrated significant associations with the tumor necrosis factor alpha-induced protein 6 gene in all probands and the integrin alpha 6 and frizzled motif associated with bone development (FRZB) genes in female probands. However, genotyping showed lack of association for a nonsynonymous single-nucleotide polymorphism in tumor necrosis factor alpha-induced protein 6, whereas a single-nucleotide polymorphism in FRZB resulting in an Arg324Gly substitution at the carboxyl terminus was associated with hip OA in the female probands (P = 0.04). This association was confirmed in an independent cohort of female hip cases (n = 338; P = 0.04). In addition, a haplotype coding for substitutions of two highly conserved arginine residues (Arg200Trp and Arg324Gly) in FRZB was a strong risk factor for primary hip OA, with an odds ratio of 4.1 (P = 0.004). FRZB encodes secreted frizzled-related protein 3, which is a soluble antagonist of wingless (wnt) signaling. Variant secreted frizzled-related protein 3 with the Arg324Gly substitution had diminished ability to antagonize wnt signaling in vitro. Hence, functional polymorphisms within FRZB confer susceptibility for hip OA in females and implicate the wnt signaling pathway in the pathogenesis of this disease.

Arginine↗
PubMed2004

Common variants within the interleukin 4 receptor alpha gene (IL4R) are associated with susceptibility to osteoarthritis.

Primary osteoarthritis (OA) is a common late-onset arthritis that demonstrates a complex mode of transmittance with both joint-site and gender-specific heterogeneity. We have previously linkage-mapped an OA susceptibility locus to a 12-cM interval at chromosome 16p12.3-p12.1 in a cohort of 146 affected female sibling-pair families ascertained by total hip replacement (female-THR families), with a maximum multipoint LOD score of 1.7. Despite the low LOD score, we were encouraged to investigate this interval further following the report of a linkage to the same interval in an Icelandic pedigree with an early-onset form of hip OA. Using public databases, we searched the interval for plausible candidates and concluded that the gene encoding the interleukin 4 receptor alpha chain (IL4R) was a particularly strong candidate based on its known role in cartilage homeostasis. We genotyped nine common single nucleotide polymorphisms (SNPs) from within IL4R, including six non-synonymous SNPs, in the 146 probands from our female-THR families (stage 1) and in an independent cohort of 310 female-THR cases (stage 2). We compared allele frequencies with those of 399 age-matched female controls. All individuals were UK Caucasians. The minor alleles of two SNPs demonstrated association in both stages, with the most significant association having a P-value of 0.004 with an odds ratio (OR) of 2.1. These two SNPs defined two associated SNP groups. Inheriting a minor SNP allele from both groups was a particular risk factor (OR=2.4, P=0.0008). Our data suggest that functional variants within the IL4R gene predispose to hip OA in Caucasian females.

Aged↗
PubMed2004

Finer linkage mapping of primary osteoarthritis susceptibility loci on chromosomes 4 and 16 in families with affected women.

OBJECTIVE: To more finely linkage-map primary osteoarthritis (OA) susceptibility loci on chromosomes 4 and 16. METHODS: Two hundred eighteen families, each with 2 or more women concordant for primary OA (ascertained by total hip replacement [THR] or total knee replacement), were genotyped using highly polymorphic microsatellite markers from chromosomes 4 and 16, at an average density of 1 marker every 4 cM. Two-point and multipoint linkage analyses were performed for all 218 families and for the 146 families from the 218 that included women concordant for THR (female-THR families). RESULTS: A single region of linkage was identified on chromosome 4q, with a maximum multipoint logarithm of odds (LOD) score (MLS) of 3.1 in the 146 female-THR families. This locus was centered 79 cM from the 4p telomere and had a 1-LOD support interval of 4 cM. Two regions of linkage were identified on chromosome 16, the first on 16p with an MLS of 1.7 in the female-THR families and the second on 16q with an MLS of 1.9 in all 218 families. The first locus was centered 46 cM and the second 89 cM from the p-telomere. The 1-LOD support intervals were 12 cM and 10 cM, respectively. CONCLUSION: Finer linkage mapping using a high density of microsatellite markers has narrowed female OA susceptibility loci on chromosomes 4 and 16. The regions have been narrowed sufficiently for association analysis.

Chromosome Mapping↗
PubMed2004

Microsatellite association mapping of a primary osteoarthritis susceptibility locus on chromosome 6p12.3-q13.

OBJECTIVE: To test a high density of microsatellite markers from within a primary osteoarthritis (OA) locus on chromosome 6 for association with OA as a means of narrowing and focusing our search for the susceptibility gene. METHODS: One hundred forty-six families, each with 2 or more women concordant for primary OA (ascertained by total hip replacement), were genotyped for 36 microsatellite markers from within a narrow interval at 6p12.3-q13 which we had previously shown to be linked to OA. Each marker was tested for linkage and for association, the latter by means of the transmission disequilibrium test and by a case-control analysis. RESULTS: The highest 2-point logarithm of odds (LOD) score was 4.8, with 11 markers having LOD scores > or =2.0. Several markers demonstrated evidence of association, in particular, a cluster of markers positioned within or near the functional candidate gene BMP5. CONCLUSION: Our linkage data reinforce the evidence of a major susceptibility locus on chromosome 6. We had previously failed to detect an association with BMP5 using gene-based single-nucleotide polymorphisms. The association data reported here prompt us to speculate that the chromosome 6 susceptibility may be coded for by cis-acting polymorphism in the regulatory elements of this gene, rather than by variation in its protein coding sequence.

Arthroplasty, Replacement, Hip↗
PubMed2004

Familial inheritance of osteoarthritis: documented family subsets.

Identifying susceptibility genes for a common complex disease is complicated by heterogeneity at several levels including allelic, locus, clinical, and population. The latter two can be alleviated by focusing on particular subsets of families that have well-defined disease. For osteoarthritis it was commonly thought that a generalized disease approach was the wisest ascertainment because this would target a systemic disease that had to have a major genetic component. However, this intuitive idea has not yet provided the breakthroughs many expected and it has become apparent that a joint-specific and gender-specific approach may be more fruitful. Large collections of osteoarthritis cohorts have been assembled either as part of prospective studies or more directly. Some of these collections have targeted specific joints, others have not. The latter are, however, amenable to stratification. Many collectors included the acquisition of DNA as a core study aim. A variety of osteoarthritis subsets are therefore available for genetic analysis. Open accessibility is another matter. Although many collections were funded partly or wholly by public or charitable organizations, they can be jealously guarded or have arcane access rights. Open access, with necessary safeguards, is something the osteoarthritis research community should strive for if progress toward susceptibility gene identification is to be swift.

Gene Library↗
PubMed2003

Estrogen receptor alpha gene haplotype is associated with radiographic osteoarthritis of the knee in elderly men and women.

OBJECTIVE: Genetic influences have been shown to play an important role in the etiology of osteoarthritis (OA), but the genes involved are ill-defined. We studied the association between polymorphisms in the estrogen receptor alpha (ERalpha) gene and the prevalence of radiographic OA of the knee. METHODS: The study group comprised 1,483 men and women from the Rotterdam Study. Direct molecular haplotyping was used to determine the relationship between 2 polymorphisms in the ERalpha gene (the Pvu II and Xba I restriction fragment-length polymorphisms). Radiographs of the knee were evaluated according to the Kellgren/Lawrence (K/L) score, along with separate scores for osteophytosis and joint space narrowing. RESULTS: Three different haplotype alleles were identified: px (54%), PX (34%), and Px (12%). Allele PX was associated with an increased prevalence of radiographic knee OA (K/L score >/=2). The prevalence of radiographic OA was 22% among subjects without allele PX, 24% among those carrying 1 copy, and 35% among subjects carrying 2 copies. The corresponding odds ratios, after adjustment for confounding factors, were 1.3 (95% confidence interval [95% CI] 0.9-1.7) for heterozygotes and 2.2 (95% CI 1.5-3.4) for homozygotes. Separate analyses for men and women showed similar risk estimates. The association appeared to be driven by osteophytosis and is somewhat consistent with the association observed in previous studies of these polymorphisms in relation to OA. CONCLUSION: This study shows that polymorphisms in the ERalpha gene are associated with radiographic OA of the knee, and in particular with osteophytosis, in both elderly men and elderly women.

Age Distribution↗