Chromatin interactions in differentiating keratinocytes reveal novel atopic dermatitis- and psoriasis-associated genes.

BACKGROUND: Hundreds of variants associated with atopic dermatitis (AD) and psoriasis, 2 common inflammatory skin disorders, have previously been discovered through genome-wide association studies (GWASs). The majority of these variants are in noncoding regions, and their target genes remain largely unclear. OBJECTIVE: We sought to understand the effects of these noncoding variants on the development of AD and psoriasis by linking them to the genes that they regulate. METHODS: We constructed genomic 3-dimensional maps of human keratinocytes during differentiation by using targeted chromosome conformation capture (Capture Hi-C) targeting more than 20,000 promoters and 214 GWAS variants and combined these data with transcriptome and epigenomic data sets. We validated our results with reporter assays, clustered regularly interspaced short palindromic repeats activation, and examination of patient gene expression from previous studies. RESULTS: We identified 118 target genes of 82 AD and psoriasis GWAS variants. Differential expression of 58 of the 118 target genes (49%) occurred in either AD or psoriatic lesions, many of which were not previously linked to any skin disease. We highlighted the genes AFG1L, CLINT1, ADO, LINC00302, and RP1-140J1.1 and provided further evidence for their potential roles in AD and psoriasis. CONCLUSIONS: Our work focused on skin barrier pathology through investigation of the interaction profile of GWAS variants during keratinocyte differentiation. We have provided a catalogue of candidate genes that could modulate the risk of AD and psoriasis. Given that only 35% of the target genes are the gene nearest to the known GWAS variants, we expect that our work will contribute to the discovery of novel pathways involved in AD and psoriasis.

HLA-B*27 is significantly enriched in Nordic patients with psoriatic arthritis mutilans.

OBJECTIVES: The genetic contribution to psoriatic disease is substantial with a dominating influence of the HLA region. The profile of HLA class I genotypes likely contributes to shaping clinical phenotypes. Herein we aimed to explore such genotypes in cohorts of closely characterised subsets of psoriatic disease with special focus on psoriatic arthritis mutilans (PAM), a severe and rare form of psoriatic arthritis (PsA). METHODS: Cohorts of patients with the diagnosis of psoriasis vulgaris with or without arthritis (n=1217), psoriasis without arthritis (n=534), psoriatic arthritis without mutilating disease (n=337) and psoriatic arthritis mutilans (n=63) were collected and genotyped for HLA class I and II genes, with standardised methodologies. Cases were compared with a healthy control population (n=2468). Case-only and case-control association tests were performed to address the hypothesis of genetic contribution to clinical phenotypes. RESULTS: The presence of HLA-B*27 was strikingly increased in PAM (45%) compared with PsA without mutilating disease (13%) and with healthy controls (13%). However, within the PAM population, HLA-B*27 did not correlate with clinical markers such as number of mutilating joints, radiographic scoring, disease duration and age of disease onset. CONCLUSIONS: HLA-B*27 emerges as an important genotype marker for PAM.

MicroRNA-146a suppresses IL-17-mediated skin inflammation and is genetically associated with psoriasis.

BACKGROUND: Psoriasis is an immune-mediated inflammatory skin disease with a strong genetic background in which activation of IL-17 signaling is central in the pathogenesis. Little has been known about the role of noncoding RNAs, including microRNAs (miRNAs), in predisposition to the disease. OBJECTIVE: We sought to investigate the genetic association of single nucleotide polymorphisms in microRNA-146a (miR-146a) to psoriasis and to explore its function in the initiation and resolution of the disease. METHODS: Analysis of the genetic association of miR-146a rs2910164 and psoriasis was carried out on 1546 patients with psoriasis and 1526 control subjects. The role of miR-146a in patients with psoriasis was assessed by using miR-146a-/- mice in conjunction with the imiquimod-induced mouse model of psoriasis. The severity of psoriasis-like skin inflammation was evaluated at morphologic, histologic, and molecular levels. miR-146a was ectopically overexpressed and inhibited in keratinocytes treated with IL-17. Synthetic miR-146a was injected intradermally into mice. RESULTS: Here we report protective association of a functional polymorphism in the miR-146a precursor (rs2910164). Genetic deficiency in miR-146a leads to earlier onset and exacerbated pathology of skin inflammation, with increased expression of IL-17-induced keratinocyte-derived inflammatory mediators, epidermal hyperproliferation, and increased neutrophil infiltration. Moreover, miR-146a-deficient mice do not resolve inflammation after discontinuation of imiquimod challenge. The overexpression of miR-146a suppressed, whereas its inhibition enhanced, IL-17-driven inflammation in keratinocytes. Functionally, miR-146a impairs the neutrophil chemoattractant capacity of keratinocytes. Finally, delivery of miR-146a mimics into the skin leads to amelioration of psoriasiform skin inflammation, decreased epidermal proliferation, and neutrophil infiltration. CONCLUSIONS: Our results define a crucial role for miR-146a in modulating IL-17-driven inflammation in the skin.

Clinical characterisation at onset of childhood psoriasis - a cross sectional study in Sweden.

Epidemiological data in childhood psoriasis are accumulating. However, reliable information captured at onset is lacking. In a cross sectional study we recruited 109 children < 16 years within 12 months of psoriasis onset and explored the clinical characteristics. Pre-pubertal children, especially boys, more often had inverse involvement (OR = 2.8, 95% CI = 1.1, 7.1, p ≤ 0.05). HLA-C*06 was positively associated with facial lesions (OR = 3.8, 95% CI = 1.5, 9.7, p < 0.01) and guttate phenotype and was more common in pubertal children. A high PASI score was not associated with overweight or early age at onset, and gender did not influence disease onset. Psoriasis can be difficult to diagnose in children, especially in pre-pubertals. Thorough examination of facial and genital areas can help in establishing the diagnosis. Our published genetic data in combination with the clinical findings presented herein indicate that puberty may separate different populations of childhood psoriasis.

Rare coding variants in NOX4 link high ROS levels to psoriatic arthritis mutilans.

Psoriatic arthritis mutilans (PAM) is the rarest and most severe form of psoriatic arthritis, characterized by erosions of the small joints and osteolysis leading to joint disruption. Despite its severity, the underlying mechanisms are unknown, and no susceptibility genes have hitherto been identified. We aimed to investigate the genetic basis of PAM by performing massive parallel sequencing in sixty-one patients from the PAM Nordic cohort. We found rare variants in the NADPH oxidase 4 (NOX4) in four patients. In silico predictions show that the identified variants are potentially damaging. NOXs are the only enzymes producing reactive oxygen species (ROS). NOX4 is specifically involved in the differentiation of osteoclasts, the cells implicated in bone resorption. Functional follow-up studies using cell culture, zebrafish models, and measurement of ROS in patients uncovered that these NOX4 variants increase ROS levels both in vitro and in vivo. We propose NOX4 as the first candidate susceptibility gene for PAM. Our study links high levels of ROS caused by NOX4 variants to the development of PAM, offering a potential therapeutic target.

Cost-effective HLA-Cw06:02 typing in a Caucasian population.

Considering the clinical and genetic heterogeneity of psoriasis which may translate into distinct disease pathology and treatment response, correct typing of the main candidate gene HLA-C is critical but not trivial. To facilitate genotyping, we compared established techniques with our newly developed tool. Here, we propose that typing of four single nucleotide polymorphic markers within the HLA-C region correctly determines HLA-Cw*06:02 genotypes in psoriatic cases and healthy controls in a population of Caucasian origin. Typing of the SNPs presented herein proved to be precise, reliable, time and cost effective, and requiring low amount of DNA.

Cognitive manic symptoms associated with the P2RX7 gene in bipolar disorder.

OBJECTIVE: Several genetic loci have been suggested to be associated with bipolar disorder but results have been inconsistent. Studying associations between bipolar symptoms and candidate genes may better expose this relationship. Here we investigate the association between bipolar key symptoms and the P2RX7 gene. METHODS: Key symptoms of mania were rated in two sets of medicated bipolar disorder patients (n=171 and n=475) at two specialized outpatient clinics for affective disorders and three regular psychiatric outpatient units in Sweden. The relationships between all manic symptoms according to DSM-IV were entered in a principal component analysis. We used a case-case model to reduce the genetic heterogeneity and tested associations between four factors related to manic symptoms and their association to four single nucleotide polymorphisms in the P2RX7 gene. RESULTS: The combination of the cognitive symptoms, distractibility, talkativeness, and thought disorder was significantly associated with rs1718119 in the P2RX7 gene in Set 1 [odds ratio (OR) = 1.78; p=0.011]. The association was re-tested in the second set (OR = 1.42; p=0.009). In the total sample, the association was even stronger (OR = 1.49; p<0.001). None of the other factors was associated with the P2RX7 gene. Within the first factor, the distractibility symptom accounted for a significant portion of the association to rs1718119 (p=0.016). CONCLUSION: There is an association between specific symptoms of bipolar disorder and the P2RX7 gene. This finding may open up new approaches to elucidating the neurobiology behind bipolar symptoms.

Long-term Outcomes and Prognosis in New-Onset Psoriasis.

IMPORTANCE: Psoriasis is a heterogeneous disease. Improved understanding of prognosis and long-term outcomes in new-onset psoriasis may improve care. OBJECTIVE: To describe the clinical course of psoriasis and identify possible indicators of long-term outcomes. DESIGN, SETTING, AND PARTICIPANTS: The Stockholm Psoriasis Cohort was a noninterventional inception cohort study enrolling patients between 2001 and 2005. The present study was conducted from January 15, 2019, to February 5, 2021. At enrollment and 10 years, patients were examined by dermatologists and rheumatologists. Data from examinations were complemented by questionnaires, medical records, and registers. A total of 721 patients with recent-onset psoriasis (<12 months duration), 15 years or older were recruited using advertising and referrals from a broad range of health care settings. MAIN OUTCOMES AND MEASURES: Disease severity and psoriatic arthritis (PsA). Recursive partitioning and regression models were implemented to identify probable indicators of long-term outcomes. RESULTS: A total of 721 patients (median [interquartile range] age, 39 [27-55] years; 405 [56%] women), including 542 (75%) with plaque-onset and 174 (24%) with guttate-onset psoriasis, were enrolled. The median follow-up was 9.6 years (interquartile range, 8.8-10.4 years). The cumulative incidence of severe psoriasis at 12 years from enrollment was 21%. Among 509 patients examined clinically after 10 years, 77 of 389 patients (20%) with plaque onset and 56 of 116 (48%) with guttate onset had minimal disease activity without treatment, and 120 of 509 (24%) had PsA. Recursive partitioning identified strata with distinct risks for severe skin disease and PsA: the cumulative incidence of severe disease in patients with plaque phenotype, above-median disease activity, and scalp lesions was 52% (95% CI, 41%-64%), compared with 11% (95% CI, 8%-14%) in patients with below-median disease activity at inclusion; and 48 of 82 patients (59%) with peripheral enthesitis had PsA after 10 years compared with 37 of 304 patients (12%) without initial joint pain (P < .001). Smoking (hazard ratio, 1.70; 95% CI, 1.10-2.63) and activating genes in the interleukin-23 (IL-23) pathway (odds ratio, 1.55; 95% CI, 1.14-2.11) were also significantly associated with a severe disease course. Systemic therapy at or before enrollment was associated with a lower risk for severe disease at 10 years compared with later initiation of systemic therapy (odds ratio, 0.24; 95% CI, 0.06-0.90). CONCLUSIONS AND RELEVANCE: The findings of this cohort study suggest that combinations of clinical characteristics at onset and activating genes in the IL-23 pathway are significantly associated with the clinical course of psoriasis, whereas joint pain and peripheral enthesitis may indicate the probability of PsA. Patients within those categories merit specialist referral and closer follow-up. The possibility of modifying the disease course with early systemic intervention should be tested.

Genetic gating of human fear learning and extinction: possible implications for gene-environment interaction in anxiety disorder.

Pavlovian fear conditioning is a widely used model of the acquisition and extinction of fear. Neural findings suggest that the amygdala is the core structure for fear acquisition, whereas prefrontal cortical areas are given pivotal roles in fear extinction. Forty-eight volunteers participated in a fear-conditioning experiment, which used fear potentiation of the startle reflex as the primary measure to investigate the effect of two genetic polymorphisms (5-HTTLPR and COMTval158met) on conditioning and extinction of fear. The 5-HTTLPR polymorphism, located in the serotonin transporter gene, is associated with amygdala reactivity and neuroticism, whereas the COMTval158met polymorphism, which is located in the gene coding for catechol-O-methyltransferase (COMT), a dopamine-degrading enzyme, affects prefrontal executive functions. Our results show that only carriers of the 5-HTTLPR s allele exhibited conditioned startle potentiation, whereas carriers of the COMT met/met genotype failed to extinguish conditioned fear. These results may have interesting implications for understanding gene-environment interactions in the development and treatment of anxiety disorders.

The prevalence of ADH1B and OPRM1 alleles predisposing for alcohol consumption are increased in the Hungarian psoriasis population.

Alcohol intake affects in great the symptoms and life of  psoriasis patients, although the association of SNPs related to increased alcohol consumption with psoriasis has not been elucidated. Therefore, to investigate the association of psoriasis with established alcohol consumption and dependence-related gene variants we conducted a population-based case-control study including 3743 subjects (776 psoriasis cases and 2967 controls from the general Hungarian population). Genotyping of 23 SNPs at ADH1B, ADH1C, ALDH1A1, ALDH2, SLC6A3, DDC, GABRA2, GABRG1, HTR1B, MAOA, TPH2, CHRM2, GRIN2A, POMC, OPRM1, OPRK1 and BDNF were determined and differences in genotype and allele distributions were investigated. Multiple logistic regression analyses were implemented. Analysis revealed association between C allele of the rs1229984 polymorphism (ADH1B gene) and psoriasis risk (ORadditive = 1.58, 95% CI 1.23-2.03, p < 0.001, ORrecessive = 1.58, 95% CI 1.22-2.04, p = 0.001). Furthermore, the G allele of rs1799971 polymorphism (OPRM1 gene) increased the risk of familial aggregation (ORadditive = 1.99, 95% CI 1.36-2.91, p < 0.001 ORdominant = 2.01, 95% CI 1.35-3.01, p < 0.001). In subgroups of psoriatic patients with history of early onset and familial aggregation effect allele 'C' of rs1229984 showed association in the additive and recessive models (ORadditive = 2.41, 95% CI 1.26-4.61, p < 0.01, ORrecessive = 2.42, 95% CI 1.26-4.68, p < 0.01). While effect allele 'G' of rs1799971 (OPRM1) also associated with increased risk of early onset and familial aggregation of psoriasis in the additive and dominant models (ORadditive = 1.75, 95% CI 1.27-2.43, p = 0.001, ORdominant = 1.82, 95% CI 1.26-2.63, p = 0.001). Our results suggest that genetically defined high-risk individuals for alcohol consumption are more common in the psoriasis population.

Association with Genetic Variants in the IL-23 and NF-κB Pathways Discriminates between Mild and Severe Psoriasis Skin Disease.

Psoriasis is clinically heterogeneous, and symptoms can vary from mild almost cosmetic symptoms to severe disease requiring systemic therapy. Biomarkers predicting disease development are lacking. Herein we explored the genetic background in two polarized cohorts of carefully phenotyped patients with long-term follow-up: consistent mild phenotype (n=696) and severe disease course requiring systemic therapy (n=715). All patients were treated at the same dermatology department ensuring homogenous assessment. Genotyping included known psoriasis-associated variants, with special focus on the IL-23 and NF-κB pathways. A case-case study comparing severe and mild psoriasis phenotypes, controlling for age at disease onset and gender, revealed significant differences between the two groups for SNPs in IL23R, NFKB1, IL21, IL12B, NFKBIL1 and IL23A. HLA-C*06 associated equally in the mild and severe disease cohorts. Strong additive effects when combining HLA-C*06 with IL23A, IL23R, IL12B, NFKB1 or TNIP1 were restricted to the severe cohort, indicating that activation of these pathways may influence disease severity in psoriasis. No protective gene was identified in the mild cohort, suggesting that current screens have primarily identified psoriasis variants associated with a more severe phenotype. These results demonstrate the importance of careful phenotyping and long-term clinical follow-up in genetic studies.

Accelerating translational research by clinically driven development of an informatics platform--a case study.

Translational medicine is becoming increasingly dependent upon data generated from health care, clinical research, and molecular investigations. This increasing rate of production and diversity in data has brought about several challenges, including the need to integrate fragmented databases, enable secondary use of patient clinical data from health care in clinical research, and to create information systems that clinicians and biomedical researchers can readily use. Our case study effectively integrates requirements from the clinical and biomedical researcher perspectives in a translational medicine setting. Our three principal achievements are (a) a design of a user-friendly web-based system for management and integration of clinical and molecular databases, while adhering to proper de-identification and security measures; (b) providing a real-world test of the system functionalities using clinical cohorts; and (c) system integration with a clinical decision support system to demonstrate system interoperability. We engaged two active clinical cohorts, 747 psoriasis patients and 2001 rheumatoid arthritis patients, to demonstrate efficient query possibilities across the data sources, enable cohort stratification, extract variation in antibody patterns, study biomarker predictors of treatment response in RA patients, and to explore metabolic profiles of psoriasis patients. Finally, we demonstrated system interoperability by enabling integration with an established clinical decision support system in health care. To assure the usefulness and usability of the system, we followed two approaches. First, we created a graphical user interface supporting all user interactions. Secondly we carried out a system performance evaluation study where we measured the average response time in seconds for active users, http errors, and kilobits per second received and sent. The maximum response time was found to be 0.12 seconds; no server or client errors of any kind were detected. In conclusion, the system can readily be used by clinicians and biomedical researchers in a translational medicine setting.

Genetic variants of the IL22 promoter associate to onset of psoriasis before puberty and increased IL-22 production in T cells.

Most psoriasis susceptibility genes were identified in cohorts of mixed clinical phenotypes and the exploration of genes in clinical subtypes is scarce. IL-22 has an established role in host defense and in psoriasis skin pathology, reflecting the delicate balance between control of infection and immunopathology. In a case-control study, we compared the genetic association to IL22 in psoriasis onset in patients between 0-9 (n=207), 10-20 (n=394), and 21-40 (n=468) years with healthy controls (n=1,529). Logistic regression analysis revealed association to regulatory elements in the IL22 promoter confined to onset of psoriasis before puberty (odds ratio=1.45, P<0.0007). The associated variants contain putative binding sites for AhR, a potent inducer of IL-22 expression. In a luciferase assay, transcriptional activity of a high-risk gene variant resulted in 80% higher promoter activity (P=0.012) compared with a low-risk variant. Ex vivo stimulated T cells from peripheral blood were analyzed with flow cytometry. Children with psoriasis carrying a high-risk variant produced 1.7 times more IL-22 compared with low-risk variants (P=0.042). Our combined genetic and functional data support the notion that a genetic IL22 variant that promotes epithelial barrier defense is preferentially enriched in and may precipitate the onset of psoriasis at an early age.

Genetic association with ERAP1 in psoriasis is confined to disease onset after puberty and not dependent on HLA-C*06.

HLA-C remains the strongest susceptibility candidate gene in psoriasis. Evidence for interaction between HLA-C and endoplasmic reticulum aminopeptidase 1 (ERAP1) confined to individuals carrying the HLA-C risk allele was recently reported. Psoriasis displays wide variation, and genetic heterogeneity is likely to contribute to clinical diversity. Age at disease onset is a putative discriminator, and separating psoriasis into early- (<40 years) and late-onset disease has been useful. To sharpen the age-dependent phenotype, we compared genotypes for ERAP1 (rs26653, rs30187, and rs27524) and HLA-C*06:02 in healthy controls and cases stratified for onset of psoriasis at <10, 10-20, 20-40, and >40 years of age. This approach revealed that association with ERAP1 was confined to cases with onset between 10 and 20 years (odds ratio 1.59, 95% confidence interval: 1.28-1.98, P=0.00008) and no association was detected in cases with onset below 10 years, reflecting genetic heterogeneity within the childhood psoriasis population. In contrast to earlier findings, association with ERAP1 was neither dependent on nor interacting with HLA-C*06:02. ERAP1 single-nucleotide polymorphism rs26653, which, to our knowledge, has not previously been reported in psoriasis, is nonsynonymous, has suggestive functional consequences, and herein displays strong association with disease.

Polymorphisms in AKR1C4 and HSD3B2 and differences in serum DHEAS and progesterone are associated with paranoid ideation during mania or hypomania in bipolar disorder.

Paranoia is commonly a mood-incongruent psychotic symptom of mania which may be related to dopamine dysregulation. Progesterone and its metabolite allopregnanolone (ALLO) have been found in animals to antagonize the effects of dopamine. We therefore examined serum progesterone, its endogenous antagonist DHEAS and polymorphisms of the genes coding for certain steroidogenetic enzymes (AKR1C4, HSD3B2, and SRD5A1) in 64 males and 96 females with bipolar 1 or 2 disorder with or without paranoid ideation during mood elevation. Euthymic morning serum progesterone, DHEAS and cortisol concentrations were measured in males and in premenopausal women who were in follicular phase and not taking oral contraceptives. In women only, SNPs in AKR1C4 reduced the likelihood of having exhibited paranoid ideation by circa 60%. The haplotype of all 4 SNPs in the AKR1C4 gene reduced the risk of exhibiting paranoia by 80% (OR 0.19, 95% CI 0.06-0.61, p=0.05). A history of paranoid ideation was not, however, related to progesterone or DHEAS concentration. Serum DHEAS and progesterone concentrations were lower in men who had shown paranoid ideation during mania/hypomania compared with those who had not (F=7.30, p=0.006) however this was not coupled to polymorphisms in the selected genes. The ancestral G in rs4659174 in HSD3B2 was in men associated with a lower risk of paranoid ideation (likelihood ratio χ(2) 3.97, p=0.046, OR 0.31 (95% CI 0.10-0.96)) but did not correlate with hormone concentrations. Hence, gene variants in the steroidogenetic pathway and steroids concentration differences may be involved in the susceptibility to paranoia during mood elevation.

P2RX7: expression responds to sleep deprivation and associates with rapid cycling in bipolar disorder type 1.

CONTEXT: Rapid cycling is a severe form of bipolar disorder with an increased rate of episodes that is particularly treatment-responsive to chronotherapy and stable sleep-wake cycles. We hypothesized that the P2RX7 gene would be affected by sleep deprivation and be implicated in rapid cycling. OBJECTIVES: To assess whether P2RX7 expression is affected by total sleep deprivation and if variation in P2RX7 is associated with rapid cycling in bipolar patients. DESIGN: Gene expression analysis in peripheral blood mononuclear cells (PBMCs) from healthy volunteers and case-case and case-control SNP/haplotype association analyses in patients. PARTICIPANTS: Healthy volunteers at the sleep research center, University of California, Irvine Medical Center (UCIMC), USA (n = 8) and Swedish outpatients recruited from specialized psychiatric clinics for bipolar disorder, diagnosed with bipolar disorder type 1 (n = 569; rapid cycling: n = 121) and anonymous blood donor controls (n = 1,044). RESULTS: P2RX7 RNA levels were significantly increased during sleep deprivation in PBMCs from healthy volunteers (p = 2.3*10(-9)). The P2RX7 rs2230912 _A allele was more common (OR = 2.2, p = 0.002) and the ACGTTT haplotype in P2RX7 (rs1718119 to rs1621388) containing the protective rs2230912_G allele (OR = 0.45-0.49, p = 0.003-0.005) was less common, among rapid cycling cases compared to non-rapid cycling bipolar patients and blood donor controls. CONCLUSIONS: Sleep deprivation increased P2RX7 expression in healthy persons and the putatively low-activity P2RX7 rs2230912 allele A variant was associated with rapid cycling in bipolar disorder. This supports earlier findings of P2RX7 associations to affective disorder and is in agreement with that particularly rapid cycling patients have a more vulnerable diurnal system.

HTR1A a novel type 1 diabetes susceptibility gene on chromosome 5p13-q13.

BACKGROUND: We have previously performed a genome-wide linkage study in Scandinavian Type 1 diabetes (T1D) families. In the Swedish families, we detected suggestive linkage (LOD≤2.2) to the chromosome 5p13-q13 region. The aim of our study was to investigate the linked region in search for possible T1D susceptibility genes. METHODOLOGY/PRINCIPAL FINDINGS: Microsatellites were genotyped in the Scandinavian families to fine-map the previously linked region. Further, SNPs were genotyped in Swedish and Danish families as well as Swedish sporadic cases. In the Swedish families we detected genome-wide significant linkage to the 5-hydroxytryptamine receptor 1A (HTR1A) gene (LOD 3.98, p<9.8×10(-6)). Markers tagging two separate genes; the ring finger protein 180 (RNF180) and HTR1A showed association to T1D in the Swedish and Danish families (p<0.002, p<0.001 respectively). The association was not confirmed in sporadic cases. Conditional analysis indicates that the primary association was to HTR1A. Quantitative PCR show that transcripts of both HTR1A and RNF180 are present in human islets of Langerhans. Moreover, immunohistochemical analysis confirmed the presence of the 5-HTR1A protein in isolated human islets of Langerhans as well as in sections of human pancreas. CONCLUSIONS: We have identified and confirmed the association of both HTR1A and RFN180, two genes in high linkage disequilibrium (LD) to T1D in two separate family materials. As both HTR1A and RFN180 were expressed at the mRNA level and HTR1A as protein in human islets of Langerhans, we suggest that HTR1A may affect T1D susceptibility by modulating the initial autoimmune attack or either islet regeneration, insulin release, or both.