Abstract
Objective. HLA-G has well recognized tolerogenic properties in physiological and nonphysiological conditions. The 3′ untranslated region (3′UTR) of the HLA-G gene has at least 3 polymorphic sites (14-bpINS/DEL, +3142C/G, and +3196C/G) described as associated with posttranscriptional influence on messenger RNA production; however, only the 14-bpINS/DEL and +3142C/G sites have been studied in systemic lupus erythematosus (SLE).
Methods. We investigated the HLA-G 3′UTR polymorphic sites (14-bpINS/DEL, +3003C/T, +3010C/G, +3027A/C, +3035C/T, +3142C/G, +3187A/G, and +3196C/G) in 190 Brazilian patients with SLE and 282 healthy individuals in allele, genotype, and haplotype analyses. A multiple logistic regression model was used to assess the association of the disease features with the HLA-G 3′UTR haplotypes.
Results. Increased frequencies were observed of the 14-bpINS (p = 0.053), +3010C (p = 0.008), +3142G (p = 0.006), and +3187A (p = 0.013) alleles, and increased frequencies of the 14-bpINS-INS (p = 0.094), +3010 C-C (p = 0.033), +3142 G-G (p = 0.021), and +3187 A-A (p = 0.035) genotypes. After Bonferroni correction, only the +3142G (p = 0.05) and +3010C (p = 0.06) alleles were overrepresented in SLE patients. The UTR-1 haplotype (14-bpDEL/+3003T/+3010G/+3027C/+3035C/+3142C/+3187G/+3196C) was underrepresented in SLE (pcorr = 0.035).
Conclusion. These results indicate that HLA-G 3′UTR polymorphic sites, particularly +3142G and +3010C alleles, were associated with SLE susceptibility, whereas UTR-1 was associated with protection against development of SLE.
Systemic lupus erythematosus (SLE) is characterized by hyperreactivity of several B and T lymphocyte populations against a myriad of self-antigens, leading to deposition of immune complexes and tissue damage1. Familial clustering of patients with SLE and disease association with many genes of the immune response confirm the involvement of genetic factors in SLE susceptibility2,3, emphasizing the role of MHC class I and II genes4,5. Important MHC class II gene associations are related to the presence of the HLA-DRB1*03 allele group in whites, the DRB1*08 allele in African Americans, and the DRB1* allele 15 in Hispanics and Egyptians6,7, and major class I associations include several allele groups such as HLA-A*01, A*03, A*11, A*23, A*26, and A*698.
Human leukocyte antigen G (HLA-G) is a nonclassical MHC class Ib molecule that has a restricted tissue distribution in nonpathological conditions. Four membrane-bound (HLA-G1 to 4) and 3 soluble HLA-G (HLA-G5 to 7) isoforms have been described, and play a pivotal role in the modulation of the maternal immune response during pregnancy, thus facilitating the tolerance of a semiallogenic fetus by the immune system cells of the mother9. The tolerogenic properties of HLA-G are primarily mediated by the interaction of the molecule with several leukocyte receptors (ILT-2, ILT-4, and KIR2DL4, among others), which may (1) inhibit cytolysis mediated by CD8+ T cells and natural killer cells10, (2) impair transendothelial migration of lymphocytes11, (3) shift the balance of cytokines to a predominant Th2 immune response12, (4) suppress T CD4+ lymphocyte proliferation13,14, and (5) induce apoptosis of activated T CD8+ cells by soluble HLA-G isoforms15,16, among others. Thus, the ectopic expression of HLA-G has been suggested as a possible mechanism of tissue protection against autoimmune inflammatory responses during the process of immune surveillance17.
The HLA-G coding region has a low level of polymorphism compared to the classical HLA genes; however, the regulatory gene regions (promoter and 3′UTR) have relevant genetic variations. In the 3′UTR of the HLA-G gene there are several polymorphic sites that define at least 15 different known haplotypes in Brazil18,19 and a number of rare haplotypes found in other populations20,21. Three of these polymorphic sites have been previously associated with the magnitude of HLA-G messenger RNA (mRNA) expression: (1) the insertion of 14 bp at position +2961 has been associated with a more stable mRNA22; (2) the +3142C/G polymorphic site has been described as influencing the binding of microRNA, particularly the +3142G allele, increasing the affinity of some microRNA for the HLA-G mRNA, thus decreasing mRNA availability23; and (3) the +3187A allele that has been associated with a less stable mRNA because of its vicinity to an adenine and uridine-rich motif24. Although the other 5 described polymorphic sites have not been studied in relation to their post-transcriptional influence on HLA-G mRNA production, they may influence the binding of several microRNA25.
There are only a few, controversial studies regarding the role of HLA-G 3′UTR in patients with SLE, evaluating only the 14-bp insertion/deletion (14-bpINS/DEL)26,27,28 and the +3142 C/G polymorphisms29. Because the polymorphic sites at HLA-G 3′UTR are in linkage disequilibrium (LD)18, 3′UTR haplotypes may differentially influence HLA-G expression, and because HLA-G has immunomodulatory properties, we evaluated the HLA-G 3′UTR polymorphic sites in patients with SLE from 2 Brazilian populations for allele, genotype, and haplotype frequencies.
MATERIALS AND METHODS
Population
We designed a case-control study encompassing 190 patients with SLE (180 women) aged 17–66 years (median 36 yrs) from 2 distinct geographical regions of Brazil, i.e., 50 patients followed at the Rheumatology Outpatient Clinic of the University Hospital of the Federal University of Pernambuco (northeastern Brazil), and 140 patients followed at the University Hospital of the School of Medicine of Ribeirão Preto, University of São Paulo (southeastern Brazil). All patients met at least 4 of the 11 criteria established by the American College of Rheumatology, revised in 1997, for the diagnosis of SLE30. Demographic, clinical, and laboratory data were obtained from medical records or from interviews (Table 1). In the northeastern population, original skin color classification of the patients (white and nonwhite followed an adaptation of the Fitzpatrick classification) and controls (white, mulatto, and black) did not use the same categorization pattern. Because of this, for the analysis of this variable all subjects were reclassified as whites or nonwhites to allow comparison. The Systemic Lupus Erythematosus Disease Activity Index (SLEDAI) was determined in 107 patients with SLE31.
A total of 283 healthy unrelated blood donors from the same geographical regions as the patients were also studied, i.e., 128 individuals from the Pernambuco Northeastern Hematology Institute and 155 from the Ribeirão Preto Blood Center, for whom data for HLA-G 3′UTR have been published18,19. The haplotype diversity between these 2 populations has been described19.
The study protocol was approved by the Ethics Committee of the Agamenon Magalhães Hospital in Pernambuco (CAAE 0091.0.236.000-11) and by the Ethics Committee of the University Hospital of Ribeirão Preto (HCRP 2234/2007), and written informed consent was obtained from all participants.
Amplification and sequencing of 3′UTR of the HLA-G gene
Genomic DNA was extracted from peripheral blood mononuclear cells using the DNAzol reagent (Invitrogen), according to the manufacturer’s instructions. The HLA-G 3′UTR was evaluated by nucleotide sequence variations between positions +2945 and +3259, as described18. Amplification was performed in a final volume of 25 μl containing 1×PCR buffer (20 mM Tris-HCl, 50 mM KCl, 1.5 mM MgCl2), 0.3 mM of each dNTP, 25 pmol of each primer (HG08F and HG08R18), 1.0 unit Taq DNA polymerase (BioTools), and 50 ng DNA. The initial denaturation cycle was carried out at 94°C for 3 min, followed by 40 cycles at 94°C for 30 s, 60°C for 60 s, 72°C for 30 s, and a final extension step at 72°C for 7 min. The amplification product was evaluated using 2% agarose gel. PCR products containing the amplified fragment of about 350 bp were directly sequenced. Individuals homozygous for the presence or absence of the 14-bp fragment were sequenced in both directions using the Big Dye Terminator kit and the ABI3100 Genetic Analyzer (Applied Biosystems). Individuals who were 14-bp heterozygous were sequenced only with the reverse primer. All polymorphic sites found in HLA-G 3′UTR were individually annotated.
Statistical analysis
Allelic and genotypic frequencies were estimated with the GENEPOP software version 4.0.1032, using Fisher’s exact test with Levene’s correction to calculate the number of expected homozygotes or heterozygotes. Adherences of genotypic proportions to Hardy-Weinberg equilibrium (HWE) expectations were estimated by the exact test of Guo and Thompson, also using the GENEPOP software33. The exact test of population differentiation, based on genotypic frequencies, was carried out with the GENEPOP program. LD between each pair of loci was evaluated for each group as well as for the entire population using the Arlequin program, version 3.5.1.234.
Given the positive LD between alleles from the studied polymorphisms, but unknown gametic phase, the most likely haplotype pair for each sample was determined by 2 independent computational methods, without taking into account any prior information. The PHASE method35 was applied using the PHASE program version 2.1. The expectation-maximization (EM) algorithm36 was also used to estimate haplotype frequencies using the Arlequin program.
To compare the allele frequencies between patients and controls we constructed 2 × 2 contingency tables, and p values were calculated using the 2-tailed Fisher’s exact test. The relative risk was estimated by calculating the OR with 95% CI. For genotype frequency analysis, tables were constructed by fixing 1 genotype and comparing it against the others. A similar strategy was applied to haplotype association studies. Analyses of contingency tables were performed using GraphPad InStat version 3.0a for Macintosh (GraphPad Software).
The association of disease features with the HLA-G 3′UTR haplotypes was assessed by a multiple logistic regression model. Covariants that showed the likelihood ratio statistic with a probability up to 0.25 in univariate analysis were included in the model using the Forward method37 and the Software R, version 2.10.1 (R Foundation for Statistical Computing).
For all analyses, p values were considered to be significant at < 0.05. For the analyses encompassing allele, genotype, and haplotype comparisons between patients and controls, p values obtained before and after Bonferroni correction (pc) were also calculated.
RESULTS
Influence of demographic variables
Patient and control groups showed differences in sex distribution, with a high frequency of females in the patient group and males among blood donors. The median age of healthy donors was slightly lower than that of patients. Ancestry information, evaluated by the perception of skin color, showed a similar distribution between white and nonwhite individuals (p = 0.886; OR 0.94, 95% CI 0.54–1.65) in the southeastern population. In the northeastern population, the proportions of whites and nonwhites differed between patients and controls; however, the multivariate analyses stratified according to skin color showed no significant differences.
Frequencies of HLA-G 3′UTR polymorphic sites differed between SLE and healthy controls
Because the 3′UTR of HLA-G gene was sequenced, all described polymorphic sites were observed, including the 14-bp INS/DEL (GenBank ID rs1704), +3003C/T (GenBank ID rs1707), +3010C/G (GenBank ID rs1710), +3027A/C (GenBank ID rs17179101), +3035C/T (GenBank ID rs17179108), +3142C/G (GenBank ID rs1063320), +3187A/G (GenBank ID rs9380142), and +3196C/G (GenBank ID rs1610696).
Considering the Brazilian population as a whole, controlled for place of origin, sex, age, and skin color, the SLE group presented differences in the allele frequencies of +3010 C (p = 0.008; OR 1.69, 95% CI 1.15–2.56), +3142 G (p = 0.006; OR 1.74, 95% CI 1.17–2.61), and +3187 A (p = 0.013; OR 1.75, 95% CI 1.12–2.78), and a borderline value for the 14-bp INS allele (p = 0.053; OR 1.49, 95% CI 1.00–2.23) in relation to controls. Some comparisons continued to be significant after Bonferroni correction; i.e., pc = 0.048 for +3142 G and a borderline value for +3010 C (pc = 0.064). After stratification according to place of origin, but still controlling for confounding variables (sex, age, and skin color), we observed important differences in 3′UTR HLA-G allele frequencies between patients with SLE and controls in each population. In the northeastern population, most allele frequencies differed significantly between the SLE group and controls, but the +3187 A allele was the only one that continued to show a significant difference after Bonferroni correction (p = 0.0003 and pc = 0.002). In contrast, in the southeastern population there were no significant differences in allele frequencies between SLE and controls after control for confounders (Table 2).
Patients from different regions showed different genotype distribution
HWE, LD, and differences in genotype distribution were determined, considering patients and controls as whole groups. None of the studied loci showed significant departures from HWE expectations (p > 0.05) in the control population; however, the 14-bp polymorphism did not fit HWE in the patient group, exhibiting a deficit of heterozygosis (p = 0.010). Overall, most polymorphic sites in the HLA-G 3′UTR presented high LD, allowing the use of probabilistic models to infer haplotypes. Exceptions are made for the +3003 T/C and +3027 A/C pair in patients and controls, and for the +3027 A/C and +3196 C/G pair in the patient group. The exact test of population differentiation based on genotype frequencies revealed different genotype distribution for the 14-bp (p = 0.037), +3010 (p = 0.001), +3142 (p = 0.007), and +3187 (p = 0.043) loci between patients with SLE and controls, considering the northeastern and southeastern populations as a whole. Differences in genotypic distribution between the southeastern and northeastern control groups were significant only for the +3003 locus (p = 0.020); and the exact test of population differentiation based on genotype frequencies revealed a similar result for the control groups of both populations (p = 0.449). Considering the whole population controlled for place of origin, sex, age, and skin color, we found an overrepresentation of +3010 C-C (p = 0.033; OR 1.96, 95% CI 1.06–3.70), +3142 G-G (p = 0.021; OR 2.04, 95% CI 1.14–3.85), and +3187 A-A (p = 0.035; OR 1.85, 95% CI 1.05–3.23) and concomitant underrepresentation of the +3010 G-G (p = 0.027; OR 0.44, 95% CI 0.21–0.92) and +3142 C-C (p = 0.034; OR 0.46, 95% CI 0.22–0.94) genotype frequencies in the SLE group. However, none of the genotype frequency differences remained significant after Bonferroni correction. Interestingly, all individuals from the patient and control groups exhibiting the 14-bp INS-INS genotype showed homozygosis for the +3010 C-C, +3142 G-G, and +3187 A-A loci as well, as detected by Castelli, et al18.
HLA-G 3′UTR haplotypes were associated with SLE susceptibility
Given the positive LD between alleles of the 3′UTR HLA-G polymorphisms, but unknown gametic phase, the expectation-maximization algorithm and the PHASE method were applied to define haplotypes from SLE patient samples, as described35,36. Haplotypes from the control southeastern18 and northeastern19 samples were defined in previous studies. In our current study, haplotypes from 2 patients with SLE were not concordant by either method and were not considered for further analysis. The remaining samples did present the same haplotype inferred by both methods, with a mean probability of 0.998 and 0.964 for the EM and PHASE algorithms, respectively. The haplotyping methods used did reveal the most frequent haplotypes, named according to our previous studies18,19.
The UTR-1 haplotype (14-bpDEL, +3003T, +3010G, +3027C, +3035C, +3142C, +3187G, +3196C) was associated with protection against development of SLE (p < 0.005; OR 0.52, 95% CI 0.33–0.82, pc = 0.035), whereas UTR-5 (14-bpINS, +3003T, +3010C, +3027C, +3035T, +3142G, +3187A, +3196C) was associated with susceptibility to the development of SLE only before Bonferroni correction (p = 0.031; OR 2.10, 95% CI 1.09–4.08, pc = 0.215; Table 3). Haplotype frequency distributions for both control populations were different when all haplotypes were considered simultaneously (p = 0.003). The haplotypes that were associated with protection from (UTR-1) and susceptibility to (UTR-5) SLE did not differ significantly between northeastern and southeastern Brazilians19.
To further explore these associations, we grouped haplotypes exhibiting shared susceptibility or protective alleles. The frequency of the occurrence of both haplotypes bearing the SLE susceptibility sequence (14-bpINS, +3010C, +3142G, +3187A) was overrepresented in patients compared to controls (p = 0.029; OR 1.67, 95% CI 1.07–2.61). Considering that UTR-1 is the only haplotype that lacks the entire sequence for susceptibility, we examined the existence of a protective consensus sequence by grouping haplotypes that lacked at least 3 of the 4 susceptibility alleles. With this strategy, we found that haplotypes lacking the 14-bpINS and +3010C alleles, i.e., UTR-1, UTR-4, UTR-6, or UTR-14, when present in homozygosis, were associated with protection against development of SLE (p = 0.018; OR 0.54, 95% CI 0.32–0.91). It is notable that when susceptibility and protective haplotypes were observed in the same individual, no statistically significant differences were observed between patients and controls (p = 0.418; OR 0.84, 95% CI 0.56–1.25). These results are shown in Table 4.
Considering that the polymorphic sites observed at the HLA-G 3′UTR were in LD, we tried to identify the most relevant ones associated with SLE susceptibility (14-bpINS/+3010C/+3142G/+3187A) by studying haplotypes that presented a partial susceptibility consensus. Regarding the role of the 14-bpINS allele, we observed that a single change of the 14-bpDEL allele in the susceptibility consensus, as observed in UTR-3, UTR-10, UTR-11, UTR-13, did not abolish its contribution to SLE susceptibility. Evidence for this: (1) a double dose of haplotypes combining full or partial susceptibility consensus lacking the 14-bpINS allele was overrepresented in the SLE patient group (p = 0.021; OR 1.60, 95% CI 1.09–2.37) even though UTR-10 and UTR-11 were present only in the control group at low frequency in our study population; and (2) the protection conferred by the double-protection consensus haplotypes was abolished after adding individuals who shared 1 protective haplotype with the susceptibility consensus, but lacking the 14-bpINS (p = 0.202; OR 0.77, 95% CI 0.52–1.13). To study the influence of the +3010 C/G polymorphic site in relation to others associated with SLE susceptibility, we compared the frequency of the haplotypes that lacked the +3010 C allele, but exhibited other susceptibility markers (UTR-8 and UTR-9). Unfortunately, these haplotypes were found only in association with previously detected protective haplotypes (UTR-1, UTR-4, and UTR-14) in the control population, which made analysis more difficult. Nevertheless, increased protection was observed with the inclusion of individuals exhibiting UTR-8 and UTR-9 in the double-protection haplotype group (p = 0.005; OR 0.47, 95% CI 0.28–0.79). In contrast, susceptibility was abolished with the inclusion of the UTR-8 and UTR-9 haplotypes in the double dose susceptibility haplotype group (p = 0.093; OR 1.46, 95% CI 0.94–2.25), suggesting that the susceptibility to SLE conferred by the +3010 C allele was independent of the 14-bpINS allele in the consensus sequence.
Specific HLA-G 3′UTR haplotypes were associated with clinical and laboratory features
The association of specific haplotypes with disease manifestations was examined only for 157 patients with SLE, because 33 cases (17%) had incomplete clinical information. Univariate analysis showed that (1) individuals carrying the UTR-3 haplotype were protected against the development of pericarditis (p = 0.037); (2) those carrying the UTR-5 haplotype exhibited fewer immunological disorders (p = 0.031), as evaluated by the presence of anti-dsDNA, anti-Sm, or antiphospholipid antibodies; and (3) individuals carrying the UTR-4 haplotype presented a 2.7-fold risk to develop oronasal ulcers and were less likely to present antinuclear antibody (ANA; p = 0.010; Table 5). Multivariate analysis adjusted for sex and age confirmed the association of the UTR-5 haplotype with fewer immunological disorders (p = 0.009; OR 0.37, 95% CI 0.17–0.78) and the association of UTR-4 with undetectable ANA (p = 0.010; OR 0.22, 95% CI 0.07–0.76). The protection conferred by the UTR-3 haplotype against the development of pericarditis (p = 0.069) was not confirmed. Comparison of homozygous protective versus homozygous susceptible haplotypes revealed no association with disease severity according to clinical profile at diagnosis, suggesting that the HLA-G 3′UTR polymorphisms are related more to susceptibility to SLE than to disease severity. This idea is supported by the lack of associations between disease activity indexes (SLEDAI) and 3′UTR haplotypes (data not shown).
DISCUSSION
A report evaluating single-nucleotide polymorphism density in the MHC region in patients with SLE showed higher densities at the HLA-DRB1, C4, TNF, HLA-B, and HLA-A loci than in other MHC subregions38. Considering that the HLA-A and HLA-G loci are in LD39,40 and that HLA-A alleles are associated with SLE8, and considering the tolerogenic properties of the HLA-G molecule, the study of the regulatory regions of the HLA-G locus in patients with SLE is pertinent, particularly 3′UTR, which has elements that may post-transcriptionally influence HLA-G expression41,42. In our study, we found the same 8 polymorphic sites in the 3′UTR of the HLA-G gene, as reported by Castelli, et al18, some of them at different frequencies when compared to controls.
To minimize the chance of making a type I error in the analysis of allele, genotype, or haplotype association with SLE, we used the Bonferroni-adjusted p level. After applying this strategy, we observed only fifth-class genetic associations (p ≤ 0.05), as classified by Manly43, i.e., these associations may be due to variation in statistical power, LD, and population stratification, and may also be due to the influence of other genetic or environmental factors. To further investigate possible limitations of the study due to small sample size, we used the confidence intervals and corresponding frequencies from data that reached significance in the whole population to calculate the power of our study, and we found a power ranging from 70% to 80%, which is considered quite good.
Regarding the 14-bp INS/DEL, our results corroborate the findings of an Italian study that showed increased frequency of the 14-bp INS allele and 14-bp INS-INS genotype in patients with SLE26. The same study reported that lower soluble levels of HLA-G (sHLA-G) were more commonly associated with the 14-bp INS-INS genotype than with the 14-bp INS-DEL and 14-bp DEL-DEL genotypes in Italian and Danish patients with SLE. However, the expression of sHLA-G and the presence of the 14-bp INS-INS genotype were not related to disease activity as evaluated by SLEDAI26. Because the 14-bp INS/DEL polymorphism is usually in LD with other polymorphic sites, it is also possible that the influence of the INDEL polymorphism may depend on other nearby genetic variations.
Different studies have shown high LD between the 14-bp and +3142 loci18,23, which we also observed. A guanine at position +3142 increases the affinity of the HLA-G mRNA 3′UTR for several microRNA, negatively regulating the HLA-G gene expression by inducing mRNA degradation or translation suppression18,23. Before correcting p values, we observed an association of the +3142 G allele (p = 0.006), the +3142 G-G genotype (p = 0.021), and the double homozygosis 14-bp INS-INS/+3142G-G with SLE. A study of patients with SLE from southeastern Brazil29 also showed a significant increase in the +3142 G allele (0.58 vs 0.47; p = 0.011) and of the +3142 G-G genotype (OR 1.90, 95% CI 1.08–3.42). In addition, the double heterozygosis 14-bp INS-DEL/+3142 C-G was associated with milder disease29. Therefore, downregulation of HLA-G and the presence of the HLA-G +3142 G allele are apparently more associated with susceptibility to SLE. Indeed, after Bonferroni correction, the association of the +3142 G allele with SLE remained significant; however, the association with the 14-bp INS allele did not, indicating that disease susceptibility may be due to the +3142 polymorphic site.
HLA-G mRNA stability has also been associated with the +3187A/G polymorphism. The presence of adenine at this position is associated with lower mRNA stability in vitro, leading to decreased expression of HLA-G24. We showed an association between SLE and the presence of the +3187 A allele and the +3187 A-A genotype that was not maintained after Bonferroni correction owing to the influence of population stratification (pc = 0.002 for the northeastern study population). Once again, a lower HLA-G mRNA availability due to the presence of the +3187 A allele may confer susceptibility to SLE. However, it is worth mentioning that both polymorphisms, i.e., +3142 and +3187, are somehow associated with each other, because almost all patients carrying the +3187 G allele also carried the +3142 C allele, and the influence of the 2 polymorphisms on HLA-G availability may be codependent. To exemplify such interaction, the only haplotype carrying both alleles associated with a more stable mRNA or less mRNA decay is UTR-1 (Table 3), and this haplotype was found to be protective against SLE development (p = 0.005; pc = 0.035), i.e., a greater HLA-G availability is apparently protective against SLE development. Notably, UTR-1 has recently been associated with high production of soluble HLA-G44.
We also found a higher frequency of the +3010 C allele (p = 0.008) and +3010 C-C genotype (p = 0.033) in patients with SLE, which lost significance after Bonferroni correction; however, the +3010 C allele still presented a trend to increased frequency (pc = 0.064). Although this polymorphic site has not yet been studied in terms of its post-transcriptional influence on mRNA production, this SNP may influence the binding of several microRNA25, thus influencing the final mRNA availability. On the other hand, the higher frequency of the +3010 C allele in SLE may reflect the low frequency of the UTR-1 among patients, because this haplotype (usually the most frequent among Brazilians and usually associated with the presence of the +3010 G allele) is quite underrepresented among patients with SLE. However, haplotypes bearing +3010 G (UTR-1, UTR-4, UTR-6, UTR-8, UTR-9, and UTR-14), regardless of the presence of 1 substitution of the 14-bp DEL, +3142 C, or +3187 G alleles, were associated with SLE protection, suggesting a particular relevance of the +3010 C allele in susceptibility to SLE.
Our data indicate that a 3′UTR HLA-G polymorphic site associated with lower HLA-G mRNA availability (+3142G) was associated with development of SLE, and a 3′UTR haplotype (UTR-1) that has been associated with high production of HLA-G was associated with protection against development of SLE. These findings are in agreement with the idea that the presence of such a tolerogenic molecule would prevent development of SLE. Together, these findings indicate that the 3′UTR of the HLA-G gene had a role in SLE development in 2 Brazilian populations that differ regarding ancestry admixture.
Acknowledgment
We thank Viviane Carvalho for invaluable technical assistance with sequencing.
Footnotes
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The Program for Technological Development in Tools for Health-PDTISFIOCRUZ provided financial support for gene sequencing. R.G. Gomes is supported by FACEPE (APQ-0184-4.01/10) and Dr. Lucena-Silva is the recipient of a postdoctoral fellowship from CNPq (PDS 150572/2011-5).
- Accepted for publication March 19, 2013.