No association between tumour necrosis factor receptor type 2 gene polymorphism and rheumatoid arthritis severity: a comparison of the extremes of phenotypes
A. H. M. van der Helm-van Mil,
P. Dieudé1,
J. J. M. Schonkeren,
F. Cornélis1 and
T. W. J. Huizinga
Department of Rheumatology, Leiden University Medical Center, Leiden, The Netherlands and 1 GenHotel, ECRAF, Université Evry-Paris-7, Evry Genopole, France
Correspondence to: A. H. M. van der Helm-van Mil, Department of Rheumatology, C4-R, Leiden University Medical Center, P.O. Box 9600, 2300 RC Leiden, The Netherlands. E-mail: AvdHelm{at}lumc.nl
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Abstract
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Objectives. To assess the association between the tumour necrosis factor receptor 2 (TNFR2) 196 M/R single-nucleotide polymorphism and rheumatoid arthritis (RA) severity by taking advantage of the extremes of phenotype that exist in arthritis.
Methods. From the Leiden Early Arthritis Cohort (1700 patients), we selected patients who initially had the diagnosis of definite or probable RA according to the ACR criteria and developed complete remission (71 patients) or had the worst progression, to destructive disease (72 patients). A group of 135 healthy controls was included. The TNFR2 genotype was determined in these groups.
Results. The extremes of phenotypes did not differ significantly in genotype distribution. No difference in genotype distribution between rheumatoid arthritis patients and healthy controls was observed.
Conclusion. Our study demonstrates that even by comparing the extremes of phenotypes no association between the TNFR2 genotype and disease severity can be detected in Caucasian patients with sporadic RA.
KEY WORDS: Rheumatoid arthritis, Tumour necrosis factor receptor 2, Single-nucleotide polymorphism, Extremes of phenotype, Severity
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Introduction
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Recent reports have suggested an association between the tumour necrosis factor receptor 2 (TNFR2) 196 M/R single-nucleotide polymorphism (SNP) and susceptibility to rheumatoid arthritis (RA), restricted to familial RA [1, 2]. Two recent studies have reported conflicting results concerning the involvement of the TNFR2 196 M/R SNP as a genetic factor in RA severity [3, 4]. Whereas Glossop et al. report no association with this SNP and radiological and functional RA severity [3], Constantin et al. recently found a worse Health Assessment Questionnaire score in patients carrying the TNFR2 196 R allele [4]. However, in both studies the distribution of severity of RA in the relatively small number of patients was limited. An association between TNFR2 196 M/R and severity would emerge best by comparing patients with the best and the worst course, e.g. comparing the extreme phenotypes. Therefore, out of a cohort of 1700 patients we selected RA patients who developed complete remission and those patients in this cohort who had the worst progression (to destructive disease). In these two unique groups of patients the TNFR2 genotype was determined.
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Patients and methods
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The Leiden Early Arthritis Cohort consists of all patients who were referred to the Department of Rheumatology of the Leiden University Medical Center with recent-onset arthritis. From 1993 to 2003, more than 1700 patients have been included and followed. Follow-up included the Health Assessment Questionnaire, Disease Activity Score and radiographs of the hands and feet at 0, 6 and 12 months and yearly thereafter [5]. To detect the patients with the best course, we selected those patients who, at entry to the cohort, had (i) symmetrical arthritis of the small joints, (ii) morning stiffness of at least 1 h and (iii) a diagnosis of definite or probable RA according to the ACR criteria, and who (iv) achieved long-term and complete remission (no signs of arthritis in the absence of disease-modifying drugs) and were therefore discharged. Patients were not discharged when less than 1 yr in remission without the use of disease-modifying drugs. In total, 78 patients fulfilled the criteria; DNA from 71 patients was available for TNFR2 genotyping. To select the patients with the most progressive disease we selected the RA patients with the highest rate of joint destruction, as measured by the Sharp/van der Heijde method, on radiographs of hands and feet after 1 yr of follow-up. Seventy-nine patients had a total score >15, and DNA from 72 patients was available. All patients included reported having Caucasian grandparents. A group of 135 healthy controls was included; all were Caucasian and had no family history of RA.
Informed patient consent was obtained and the study was approved by the local medical ethics committee under code P23794.
Genotyping of the TNFR2 196 M/R polymorphism was performed blind, by polymerase chain reactionrestriction fragment polymorphism (N1a III), as described previously [6].
Two samples of 71 and 72 patients provides a power of 82% to detect differences with 95% confidence and an odds ratio of 3 based on a 196R allele frequency of 22%.
The
2 test was used to compare the genotype distribution between the two groups of RA patients. All allele and genotype frequencies were in HardyWeinberg equilibrium.
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Results
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The frequencies of the 196M and 196R alleles among the 143 RA patients were 78 and 22% respectively. Table 1 depicts the patients characteristics and the genotype distributions of both groups of RA patients and of the healthy controls. In the remission group, 49 patients (69%) had fulfilled the ACR criteria for definite RA and 22 patients (31%) the ACR criteria for probable RA. The extremes of phenotype did not differ significantly in genotype distribution, whether determined in the total group of patients or when the assessment was first done in one half of the patients and then replicated in the second half. In addition, there was no significant difference in Health Assessment Questionnaire and Disease Activity Score when the 196R and 196M alleles were compared (data not shown). No difference in genotype distribution between RA patients and healthy controls was observed (Table 1). Patients in the severe progression group were more frequently positive for the shared epitope than patients in the remission group (odds ratio 5.2, 95% confidence interval 2.311.7) (Table 1).
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TABLE 1. Characteristics of TNFR2 196 M/R gene polymorphism in RA patients with complete remission and severe progression
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Discussion
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In this study, no association was observed between the TNFR2 196 M/R gene polymorphism and severity in Caucasian patients with sporadic RA. By comparing the genotypes of the patients with the worst and the best course in a cohort of more than 1700 patients, an association between TNFR2 and severity, if present, would very likely have been detected. With the sample sizes used, we have a power of 82% to detect differences with an odds ratio of 3. In general, the numbers used in a power calculation are based on the difference between a normal population of RA patients that contains many phenotypes and a healthy control population that contains some phenocopies. In this circumstance a power of 80% to detect differences with an odds ratio of 2 is usually accepted. In the present study the power was enhanced by selection of extremes of phenotype. This method is supposed to increase the difference and can make a study more powerful. Therefore, in this study we accepted the magnitude of the odds ratio to be at least 3. The odds ratio for the association between HLA-class II alleles and RA severity is about 3 in inception cohorts [7]. In our design, we observed an odds ratio for shared epitope positivity and RA severity of 5, indicating the power of the present approach.
The allele and genotype distributions in this Dutch study are similar to those in French [2, 4], British [3], Italian [8] and Swedish [9] studies, in which allele frequencies of 7579% are reported for the 196M allele and 2025% for the 196R allele. The fact that in the present study the gene distributions of patients and healthy controls were comparable confirms previous findings of the lack of association between TNFR2 and susceptibility to sporadic RA [1, 2].
The TNFR2 gene is located on chromosome 1p36 and consists of 10 exons and nine introns. An SNP at codon 196 in exon 6 (ATG
AGG) results in a non-conservative amino acid substitution: methionine (M)
arginine (R). Little is known about the functionality of this amino acid substitution. In Japanese patients with systemic lupus erythematosus (SLE), it has been demonstrated that the 196 TNFR2 SNP has no influence on receptor binding of TNF-
or on receptor shedding, but that the 196R allele more effectively transduces signals for interleukin 6 production than does the 196 M allele [10]. However, in these Japanese SLE patients the 196R allele was not associated with disease severity [10].
In summary, our study demonstrates that, even by comparing the extremes of phenotypes, no association between the TNFR2 genotype and disease severity can be detected in Caucasian patients with sporadic RA.
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Acknowledgments
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The authors are indebted to the Association Francaise des Polyarthritiques and the Association Rhumatisme et Travail for funding the genotyping.
The authors have declared no conflicts of interest.
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References
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- Barton A, John S, Ollier WER, Silman A, Worthington J. Association between rheumatoid arthritis and polymorphism of tumor necrosis factor receptor II, but not tumor necrosis factor receptor I, in caucasians. Arthritis Rheum 2001;44:615.[CrossRef][ISI][Medline]
- Dieudé P, Petit E, Cailleau-Moindrault S et al. Association between tumor necrosis factor receptor II and familial but not sporadic rheumatoid arthritis, Evidence for genetic heterogeneity. Arthritis Rheum 2002;46:203944.[CrossRef][ISI][Medline]
- Glossop JR, Nixon NB, Dawes PT, Hassell AB, Mattey DL. No association of polymorphisms in the tumor necrosis factor receptor I and receptor II genes with disease severity in rheumatoid arthritis. J Rheumatol 2003;30:14069.[ISI][Medline]
- Constantin A, Dieude P, Lauwers-Cances V et al. Tumor necrosis factor receptor 2 gene polymorphism and severity of rheumatoid arthritis. Arthritis Rheum 2004;50:7427.[CrossRef][ISI][Medline]
- Aken J, Bilsen JAM, Allaart CF, Huizinga TWJ, Breedveld FC. The Leiden Early Arthritis Clinic. Clin Exp Rheumatol 2003;21(Suppl. 31):S1005.
- Al-Ansari AS, Ollier WE, Villarreal J, Ordi J, Teh LS, Hajeer AH. Tumor necrosis factor receptor II (TNFRII) exon 6 polymorphism in systemic lupus erythematosus. Tissue Antigens 2000;55:979.[CrossRef][ISI][Medline]
- Kaltenhäuser S, Wagner U, Schuster E et al. Immunogenetic markers and seropositivity predict radiological progression in early rheumatoid arthritis independent of disease activity. J Rheumatol 2001;28:73544.[ISI][Medline]
- Fabris M, Tolusso B, Di Pol E, Assaloni R, Sinigaglia L, Ferraccioli G. Tumor necrosis factor-alpha receptor two polymorphism in patients from southern Europe with mildmoderate and severe rheumatoid arthritis. J Rheumatol 2002;29:184750.[ISI][Medline]
- Dahlqvist SR, Årlestig L, Sikström C, Linghult S. Tumor necrosis factor receptor type II (exon 6) and interleukin-6 (-174) gene polymorphisms are not associated with family history but tumor necrosis factor receptor type II is associated with hypertension in patients with rheumatoid arthritis in patients from northern Sweden. Arthritis Rheum 2002;46:30968.[CrossRef][ISI][Medline]
- Morita C, Horiuchi T, Hatta N et al. Association of tumor necrosis factor receptor type II polymorphism 196R with systemic lupus erythematosus in the Japanese. Arthritis Rheum 2001;44:281927.[CrossRef][ISI][Medline]
Submitted 31 March 2004;
revised version accepted 18 June 2004.