Fine-scale mapping of type I allergy candidate loci suggests central susceptibility genes on chromosomes 3q, 4q and Xp

Chinese Society of Allergy Guidelines for Diagnosis and Treatment of Allergic Rhinitis

Allergic rhinitis (AR) is a global health problem that causes major illnesses and disabilities worldwide. Epidemiologic studies have demonstrated that the prevalence of AR has increased progressively over the last few decades in more developed countries and currently affects up to 40% of the population worldwide. Likewise, a rising trend of AR has also been observed over the last 2-3 decades in developing countries including China, with the prevalence of AR varying widely in these countries. A survey of self-reported AR over a 6-year period in the general Chinese adult population reported that the standardized prevalence of adult AR increased from 11.1% in 2005 to 17.6% in 2011. An increasing number of Journal Articles and imporclinical trials on the epidemiology, pathophysiologic mechanisms, diagnosis, management and comorbidities of AR in Chinese subjects have been published in international peer-reviewed journals over the past 2 decades, and substantially added to our understanding of this disease as a global problem. Although guidelines for the diagnosis and treatment of AR in Chinese subjects have also been published, they have not been translated into English and therefore not generally accessible for reference to non-Chinese speaking international medical communities. Moreover, methods for the diagnosis and treatment of AR in China have not been standardized entirely and some patients are still treated according to regional preferences. Thus, the present guidelines have been developed by the Chinese Society of Allergy to be accessible to both national and international medical communities involved in the management of AR patients. These guidelines have been prepared in line with existing international guidelines to provide evidence-based recommendations for the diagnosis and management of AR in China.

Critical role of Toll-like receptors in pathophysiology of allergic asthma

Allergic asthma is an airway disease, characterized by reversible bronchoconstriction, chronic inflammation of the airway, and thickness of smooth muscle in the respiratory tract. Asthma is orchestrated by an excessive Th2-adaptive immune response, in which innate immunity plays a key role. Recently TLRs have received more and more attention as they are central to orchestrate the innate immune responses. TLRs are localized as integral membrane or intracellular glycoproteins with those on the cell surface sensing microbial antigens and the ones, localized in intracellular vesicles, sensing microbial nucleic acid species. Having recognized microbial antigens, TLRs conduct the immune response towards a pro- or anti-allergy response. As a double-edged sword, they could initiate either harmful or helpful responses by the immune system in case of allergic asthma. In the current review, we will describe the role of TLRs and their signaling pathways in allergic asthma.

Characterization of genetic variation in TLR8 in relation to allergic rhinitis

BACKGROUND

A previous investigation of all 10 TLR genes for associations with allergic rhinitis (AR) detected a number of significant SNPs in the TLR8 locus. The associations indicated that an accumulation of rare variants could explain the signal. This study therefore searches for rare variants in the TLR8 region and also investigates the reproducibility of previous SNP associations.

METHODS

The TLR8 gene was resequenced in 288 AR patients from Malmö and the data were compared with publically available data. Seven previously AR-associated SNPs from TLR8 were analyzed for AR associations in 422 AR patients and 859 controls from the BAMSE cohort. The associations detected in present and previous studies were compared.

RESULTS

Sequencing detected 13 polymorphisms (three promotor and 10 coding) among 288 AR patients. Four of the coding polymorphisms were rare (MAF < 1%) and three of those were novel. Two coding polymorphisms were benign missense mutations and the rest were synonymous. Comparison with 1000Genomes and Exome Aggregation Consortium data revealed no accumulation of rare variants in the AR cases. The AR association tests made using the BAMSE cohort yielded five P-values <0.05. Tests of IgE levels yielded four significant SNP associations to birch pollen. Comparing results between different populations revealed opposing risk alleles, different gender effects, and response to different allergens in the different populations.

CONCLUSIONS

Rare variants in TLR8 are not associated with AR. Comparison of present and previous association studies reveals contradictory results for common variants. Thus, no associations exist between genetic variation in TLR8 and AR.

Toll-like receptor 7 gene deficiency and early-life Pneumovirus infection interact to predispose toward the development of asthma-like pathology in mice

BACKGROUND

Respiratory tract viruses are a major environmental risk factor for both the inception and exacerbations of asthma. Genetic defects in Toll-like receptor (TLR) 7-mediated signaling, impaired type I interferon responses, or both have been reported in asthmatic patients, although their contribution to the onset and exacerbation of asthma remains poorly understood.

OBJECTIVE

We sought to determine whether Pneumovirus infection in the absence of TLR7 predisposes to bronchiolitis and the inception of asthma.

METHODS

Wild-type and TLR7-deficient (TLR7(-/-)) mice were inoculated with the rodent-specific pathogen pneumonia virus of mice at 1 (primary), 7 (secondary), and 13 (tertiary) weeks of age, and pathologic features of bronchiolitis or asthma were assessed. In some experiments infected mice were exposed to low-dose cockroach antigen.

RESULTS

TLR7 deficiency increased viral load in the airway epithelium, which became sloughed and necrotic, and promoted an IFN-α/β(low), IL-12p70(low), IL-1β(high), IL-25(high), and IL-33(high) cytokine microenvironment that was associated with the recruitment of type 2 innate lymphoid cells/nuocytes and increased TH2-type cytokine production. Viral challenge of TLR7(-/-) mice induced all of the cardinal pathophysiologic features of asthma, including tissue eosinophilia, mast cell hyperplasia, IgE production, airway smooth muscle alterations, and airways hyperreactivity in a memory CD4(+) T cell-dependent manner. Importantly, infections with pneumonia virus of mice promoted allergic sensitization to inhaled cockroach antigen in the absence but not the presence of TLR7.

CONCLUSION

TLR7 gene defects and Pneumovirus infection interact to establish an aberrant adaptive response that might underlie virus-induced asthma exacerbations in later life.

Asthma and rhinitis: what is the relationship?

PURPOSE OF REVIEW

Asthma and rhinitis are commonly associated and they influence their respective control. New observations have contributed to better understand how to assess those conditions and how they influence each other.

RECENT FINDINGS

Recent studies found that not only the intensity, but also the duration of rhinitis could be correlated with the development of asthma and possibly its remission. The measure of exhaled nitric oxide (FeNO) has been used to show the presence of lower airway inflammation in rhinitic patients, with or without asthma. Furthermore, it has been shown that allergic rhinitis could affect asthma control in children as in adults, and consequently suggested that allergic rhinitis and asthma should be concomitantly approached in regard to their diagnosis and treatment. Additional observations showed improvements in various asthma outcomes with the treatment of rhinitis.

SUMMARY

These new data confirm the strong link between asthma and rhinitis, the importance of their interactions, and the need to identify and treat rhinitis adequately in asthmatic patients.

Toll-like receptor gene polymorphisms are associated with allergic rhinitis: a case control study

Background

The Toll-like receptor proteins are important in host defense and initiation of the innate and adaptive immune responses. A number of studies have identified associations between genetic variation in the Toll-like receptor genes and allergic disorders such as asthma and allergic rhinitis. The present study aim to search for genetic variation associated with allergic rhinitis in the Toll-like receptor genes.

Methods

A first association analysis genotyped 73 SNPs in 182 cases and 378 controls from a Swedish population. Based on these results an additional 24 SNPs were analyzed in one Swedish population with 352 cases and 709 controls and one Chinese population with 948 cases and 580 controls.

Results

The first association analysis identified 4 allergic rhinitis-associated SNPs in the TLR7-TLR8 gene region. Subsequent analysis of 24 SNPs from this region identified 7 and 5 significant SNPs from the Swedish and Chinese populations, respectively. The corresponding risk-associated haplotypes are significant after Bonferroni correction and are the most common haplotypes in both populations. The associations are primarily detected in females in the Swedish population, whereas it is seen in males in the Chinese population. Further independent support for the involvement of this region in allergic rhinitis was obtained from quantitative skin prick test data generated in both populations.

Conclusions

Haplotypes in the TLR7-TLR8 gene region were associated with allergic rhinitis in one Swedish and one Chinese population. Since this region has earlier been associated with asthma and allergic rhinitis in a Danish linkage study this speaks strongly in favour of this region being truly involved in the development of this disease.

A genome-wide search for linkage to allergic rhinitis in Danish sib-pair families

Allergic rhinitis (AR) is a complex disorder with a polygenic, multifactorial aetiology. Twin studies have found the genetic contribution to be substantial. We collected and clinically characterised a sample consisting of 127 Danish nuclear families with at least two siblings suffering from AR or allergic conjunctivitis including 540 individuals (286 children and 254 parents). A whole-genome linkage scan, using 424 microsatellite markers, was performed on both this sample and an earlier collected sample consisting of 130 families with atopic dermatitis and other atopic disorders. A third sib-pair family sample, which was previously collected and genotyped, was added to the analysis increasing the total sample size to 357 families consisting of 1508 individuals. In total, 190 families with AR was included. The linkage analysis software Genehunter NPL, Genehunter MOD, and Genehunter Imprinting were used to obtain nonparametric and parametric linkage results. Family-based association analysis of positional candidate SNPs was carried out using the FBAT program. We obtained genome-wide significant linkage to a novel AR locus at 1p13 and suggestive linkage to two novel regions at 1q31-q32 and 20p12, respectively. Family-based association analysis of SNPs in the candidate locus DNND1B/CRB1 at 1q31 showed no significant association and could not explain the linkage signal observed. Suggestive evidence of linkage was also obtained at three AR loci previously reported (2q14-q23, 2q23, and 12p13) and indication of linkage was observed at a number of additional loci. Likely maternal imprinting was observed at 2q23, and possible maternal imprinting at 3q28.

Allergic rhinitis and genetic components: focus on Toll-like receptors (TLRs) gene polymorphism

Allergic rhinitis represents a global health issue affecting 10% to 25% of the population worldwide. Over the years, studies have found that allergic diseases, including allergic rhinitis, are associated with immunological responses to antigens driven by a Th2-mediated immune response. Because Toll-like receptors (TLRs) are involved in both innate and adaptive immune responses to a broad variety of antigens, the association between polymorphisms of TLRs and allergic diseases has been the focus in many animal and human studies. Although the etiology of allergic rhinitis is still unknown, extensive research over the years has confirmed that the underlying causes of allergic diseases are due to many genetic and environmental factors, along with the interactions among them, which include gene-environment, gene-gene, and environment-environment interactions. Currently, there is great inconsistency among studies mainly due to differences in genetic background and unique gene-environment interactions. This paper reviews studies focusing on the association between TLR polymorphisms and allergic diseases, including allergic rhinitis, which would help researchers better understand the role of TLR polymorphisms in the development of allergic rhinitis, and ultimately lead to more efficient therapeutic interventions being developed.

High-level expression of early growth response-1 and association of polymorphism with total IgE and atopy in allergic rhinitis adults

BACKGROUND

Early growth response-1 (Egr-1) is expressed in human airways and its polymorphisms have been associated with total IgE and atopy in asthmatic patients. We investigated the effects of Chinese-tagging single nucleotide polymorphism (SNP) of Egr-1 and its mRNA expression on allergic rhinitis (AR) traits.

METHODS

Among 214 Chinese AR adults and 259 controls, tag SNP -4071 A-->G was genotyped and mRNA expression in peripheral blood was quantified by real-time PCR.

RESULTS

Egr-1 mRNA expression was significantly higher in patients than controls (median of 0.23 vs 0.15 fold GAPDH expression; p<0.001). Its expression was not associated with -4071 polymorphism. However, significant correlations were found between -4071 A-->G with increased plasma total IgE (p=0.028) and atopy (p=0.030) in patients. Logistic regression confirmed the association (p=0.034) with age and gender adjusted. Patients homozygous for the A allele had a 2.3-fold and 1.9-fold risks, respectively of having increased plasma total IgE and atopy than those G allele carriers.

CONCLUSIONS

We showed high levels of Egr-1 mRNA expression and demonstrated a significant association of polymorphism with increased plasma total IgE and atopy in AR patients. It may be useful to explore the pharmacogenetics of Egr-1 inhibitors.

Global expression profiling in atopic eczema reveals reciprocal expression of inflammatory and lipid genes

BACKGROUND

Atopic eczema (AE) is a common chronic inflammatory skin disorder. In order to dissect the genetic background several linkage and genetic association studies have been performed. Yet very little is known about specific genes involved in this complex skin disease, and the underlying molecular mechanisms are not fully understood.

METHODOLOGY/FINDINGS

We used human DNA microarrays to identify a molecular picture of the programmed responses of the human genome to AE. The transcriptional program was analyzed in skin biopsy samples from lesional and patch-tested skin from AE patients sensitized to Malassezia sympodialis (M. sympodialis), and corresponding biopsies from healthy individuals. The most notable feature of the global gene-expression pattern observed in AE skin was a reciprocal expression of induced inflammatory genes and repressed lipid metabolism genes. The overall transcriptional response in M. sympodialis patch-tested AE skin was similar to the gene-expression signature identified in lesional AE skin. In the constellation of genes differentially expressed in AE skin compared to healthy control skin, we have identified several potential susceptibility genes that may play a critical role in the pathological condition of AE. Many of these genes, including genes with a role in immune responses, lipid homeostasis, and epidermal differentiation, are localized on chromosomal regions previously linked to AE.

CONCLUSIONS/SIGNIFICANCE

Through genome-wide expression profiling, we were able to discover a distinct reciprocal expression pattern of induced inflammatory genes and repressed lipid metabolism genes in skin from AE patients. We found a significant enrichment of differentially expressed genes in AE with cytobands associated to the disease, and furthermore new chromosomal regions were found that could potentially guide future region-specific linkage mapping in AE. The full data set is available at http://microarray-pubs.stanford.edu/eczema.

Evidence for an asthma risk locus on chromosome Xp: a replication linkage study

BACKGROUND

Asthma is a complex genetic disorder characterized by chronic inflammation in the airways. Identification of genetic risk factors for asthma has been complicated due to genetic heterogeneity and influence from environmental risk factors. Despite the fact that multiple genetic linkage studies have been carried out the results are still conflicting and call for replication experiments. A Danish genome-wide scan has prior reported evidence for candidate regions for asthma susceptibility genes on chromosomes 1p, 5q, 6p, 12q and Xp. Linkage to chromosome 12q was later confirmed in the same replication sample as used in the present study. The aim of the study was to replicate linkage to candidate regions for asthma in an independent Danish sample.

METHODS

We performed a replication study investigating linkage to candidate regions for asthma on chromosomes 1p36.31-p36.21, 5q15-q23.2, 6p24.3-p22.3, and Xp22.31-p11.4 using additional markers in an independent set of 136 Danish asthmatic sib pair families.

RESULTS

Nonparametric multipoint linkage analyses yielded suggestive evidence for linkage to asthma to chromosome Xp21.2 (MLS 2.92) but failed to replicate linkage to chromosomes 1p36.31-p36.21, 5q15-q23.2 and 6p24.3-p22.3.

CONCLUSIONS

The replication results provide evidence for chromosome Xp21 to harbour a susceptibility gene for asthma in the Danish population. To our knowledge, the study is the first to replicate evidence for linkage to chromosome X. A susceptibility gene for asthma on chromosome X could potentially explain observed gender differences in asthma prevalence.

Genome-wide screen for asthma in Puerto Ricans: evidence for association with 5q23 region

While the number of success stories for mapping genes associated with complex diseases using genome-wide association approaches is growing, there is still much work to be done in developing methods for such studies when the samples are collected from a population, which may not be homogeneous. Here we report the first genome-wide association study to identify genes associated with asthma in an admixed population. We genotyped 96 Puerto Rican moderate to severe asthma cases and 88 controls as well as 109 samples representing Puerto Rico's founding populations using the Affymetrix GeneChip Human Mapping 100K array sets. The data from samples representing Puerto Rico's founding populations was used to identify ancestry informative markers for admixture mapping analyses. In addition, a genome-wide association analysis using logistic regression was performed on the data. Although neither admixture mapping nor regression analysis gave any significant association with asthma after correction for multiple testing, an overlap analysis using the top scoring SNPs from different methods suggested chromosomal regions 5q23.3 and 13q13.3 as potential regions harboring genes for asthma in Puerto Ricans. The validation analysis of these two regions in 284 Puerto Rican asthma trios gave significant association for the 5q23.3 region. Our results provide strong evidence that the previously linked 5q23 region is associated with asthma in Puerto Ricans. The detection of causative variants in this region will require fine mapping and functional validation.

A variant of the myosin light chain kinase gene is associated with severe asthma in African Americans

Asthma is a complex phenotype influenced by environmental and genetic factors for which severe irreversible structural airway alterations are more frequently observed in African Americans. In addition to a multitude of factors contributing to its pathobiology, increased amounts of myosin light chain kinase (MLCK), the central regulator of cellular contraction, have been found in airway smooth muscle from asthmatics. The gene encoding MLCK (MYLK) is located in 3q21.1, a region noted by a number of genome-wide studies to show linkage with asthma and asthma-related phenotypes. We studied 17 MYLK genetic variants in European and African Americans with asthma and severe asthma and identified a single non-synonymous polymorphism (Pro147Ser) that was almost entirely restricted to African populations and which was associated with severe asthma in African Americans. These results remained highly significant after adjusting for proportions of ancestry estimated using 30 unlinked microsatellites (adjusted odds ratio: 1.76 [95% confidence interval, CI: 1.17-2.65], p = 0.005). Since all common HapMap polymorphisms in approximately 500 kb contiguous regions have low-to-moderate linkage disequilibrium with Pro147Ser, we speculate that this polymorphism is causally related to the severe asthma phenotype in African Americans. The association of this polymorphism, located in the N-terminal region of the non-muscle MLCK isoform, emphasizes the potential importance of the vascular endothelium, a tissue in which MLCK is centrally involved in multiple aspects of the inflammatory response, in the pathogenesis of severe asthma. This finding also offers a possible genetic explanation for some of the more severe asthma phenotype observed in African American asthmatics.

Assessment for microsatellite DNA instability in nasal cytology samples of patients with allergic rhinitis

BACKGROUND

Genetic alterations, including microsatellite instability (MSI) and loss of heterozygosity (LOH), have been described in both malignant and benign diseases. Previous studies have successfully detected such alterations in sputum samples of patients with bronchial asthma (BA). The aim of this study was to assess the presence of MSI and/or LOH in nasal cytology samples of patients with allergic rhinitis (AR).

METHODS

Nasal brush samples and peripheral blood from 20 patients with AR were analyzed. DNA was extracted and analyzed for MSI and LOH using the following microsatellite markers: D16S289, D4S2394, D4S1651, DXS8039, D3S3606, and D2S2113, harboring potential susceptibility genes for AR and atopy. Microsatellite analysis was performed also in eight control subjects.

RESULTS

No MSI and/or LOH were noted in either the AR or the control group.

CONCLUSION

Although MSI and LOH are detectable phenomena in sputum samples of patients with BA, this seems not to be the case for nasal cytology samples of patients with AR. Additional studies are needed, using a larger number of polymorphic markers, to assess if such a difference exists among two diseases otherwise very closely related.

A functional CD86 polymorphism associated with asthma and related allergic disorders

BACKGROUND

Several studies have documented a substantial genetic component in the aetiology of allergic diseases and a number of atopy susceptibility loci have been suggested. One of these loci is 3q21, at which linkage to multiple atopy phenotypes has been reported. This region harbours the CD86 gene encoding the costimulatory B7.2 protein. The costimulatory system, consisting of receptor proteins, cytokines and associated factors, activates T cells and regulates the immune response upon allergen challenge.

METHODS

We sequenced the CD86 gene in patients with atopy from 10 families that showed evidence of linkage to 3q21. Identified polymorphisms were analysed in a subsequent family-based association study of two independent Danish samples, respectively comprising 135 and 100 trios of children with atopy and their parents. Functional analysis of the costimulatory effect on cytokine production was performed in an autologous cell-based system based on cells expressing CD86 variants.

RESULTS

Two polymorphisms were identified, encoding the amino acid changes Ile179Val and Ala304Thr, respectively. Significant associations were observed between the Ile179Val polymorphism and allergy phenotypes in both samples (eg, asthma, p = 4 x 10(-3) in the two samples combined). The undertransmitted (protective) Val179 allele was found to induce higher production of both Th1 and Th2 cytokines than the overtransmitted (risk) Ile179 allele, suggesting a functional impact of the polymorphism.

CONCLUSION

The CD86 gene, and specifically the Ile179Val polymorphism, may be a novel aetiological factor in the development of asthma and related allergic disorders.

Pigmentary changes and atopic dermatitis in a patient with Seckel syndrome

Seckel syndrome is a very rare form of primordial dwarfism characterized by antenatal and postnatal growth delay, proportionate extreme short stature, a prominent beak-like nose, hypoplasia of the malar area, small chin, microcephaly, deformed ears lacking lobules, skeletal malformations, mental retardation, and developmental delay. This syndrome has been described with associated disorders of orthopedic, neurologic, hematologic, cardiac, and ocular systems; however, only a few reports mention dermatologic involvement. We describe a 5-year-old girl with classic Seckel syndrome who presented with moderately severe atopic dermatitis and diffuse hypopigmented macules and papules.

Family based association analysis of the IL2 and IL15 genes in allergic disorders

Allergic diseases affect an increasing number of individuals and are a major global health problem. A substantial genetic contribution in the aetiology of allergic diseases is well documented. We have previously reported linkage of allergic diseases and atopy to the region harbouring the IL2 gene (4q27). IL15 is located approximately 20 Mb distal to IL2. The two genes encode cytokines that are structurally and functionally related, both inducing T-cell activation and proliferation. We screened the two genes for sequence variation and applied the seven single-nucleotide polymorphisms (SNPs) identified in a family based association study of two Danish samples comprising a total of 235 families with allergic diseases. None of the IL15 SNPs showed significant association and the haplotype analysis yielded inconsistent results in the two samples. In contrast, the two IL2 SNPs showed association both separately and in haplotypes with several atopic phenotypes, most significantly with IgE-mediated allergy. (single SNP P-value 0.0005 for positive skin prick test, haplotype P-value 0.019 for positive RAST test). To our knowledge, this is the first study reporting association between IL2 and IgE-mediated allergy, asthma and atopic eczema. The SNP (rs2069762) that showed the most consistent results is located in the promoter and has previously been shown to influence the level of IL2 expression. We suggest that the observed overtransmission of the T allele of this SNP may convey increased susceptibility to allergic disease by skewing the Th1/Th2 balance towards Th2.

Highly significant linkage to chromosome 3q13.31 for rhinitis and related allergic diseases

BACKGROUND

Allergic diseases such as asthma and rhinitis have closely related phenotypes and often occur with atopy. They show strong familial and intra-individual clustering, suggesting overlapping disease aetiology. Various loci and candidate genes have been suggested to underlie allergy. Many or all are still inconclusive. Following genome-wide scans on multiple phenotypes, we previously suggested that chromosome 3q13.12-q21.2 harbours an allergy locus.

OBJECTIVE

To identify candidate loci in the Danish population, two additional independent sets of sib-pair families were fine-scale mapped in candidate regions showing maximum likelihood scores (MLS) > or =1.5 in the genome-wide scans.

RESULTS

Twenty eight microsatellite markers in a denser map on chromosome 3q were analysed in 236 allergy sib-pair families including 125 sib pairs with rhinitis. We report significant evidence for linkage to chromosome 3q13.31 for rhinitis (MLS 5.55, identity by descent (IBD) 63.9%) and atopy (increased specific immunoglobulin E) (MLS 3.71, IBD 61.7%). We obtained an MLS of 5.1 (IBD 67.3%) at 3q13.31 when sib pairs with both rhinitis and atopy were analysed.

CONCLUSION

This study reports the first statistically significant evidence for a genetic susceptibility locus for rhinitis and to our knowledge shows the most significant evidence to date of linkage for any allergy phenotype.

Significant linkage to chromosome 12q24.32-q24.33 and identification of SFRS8 as a possible asthma susceptibility gene

BACKGROUND

Asthma is a complex genetic disorder. Many studies have suggested that chromosome 12q harbours a susceptibility gene for asthma and atopy. Linkage on chromosome 12q24.21-q24.33 was investigated in 167 Danish families with asthma.

METHODS

A two step procedure was used: (1) a genome-wide scan in one set of families followed by (2) fine scale mapping in an independent set of families in candidate regions with a maximum likelihood score (MLS) of > or =1.5 in the genome-wide scan. Polymorphisms in a candidate gene in the region on 12q24.33 were tested for association with asthma in a family based transmission disequilibrium test.

RESULTS

An MLS of 3.27 was obtained at 12q24.33. The significance of this result was tested by simulation, resulting in a significant empirical genome-wide p value of 0.018. To our Knowledge, this is the first significant evidence for linkage on chromosome 12q, and suggests a candidate region distal to most previously reported regions. Three single nucleotide polymorphisms in splicing factor, arginine/serine-rich 8 (SFRS8) had an association with asthma (p < or = 0.0020-0.050) in a sample of 136 asthmatic sib pairs. SFRS8 regulates the splicing of CD45, a protein which, through alternative splice variants, has an essential role in activating T cells. T cells are involved in the pathogenesis of atopic diseases such as asthma, so SFRS8 is a very interesting candidate gene in the region.

CONCLUSIONS

Linkage and simulation studies show that the very distal part of chromosome 12q contains a gene that increases the susceptibility to asthma. SFRS8 could act as a weak predisposing gene for asthma in our sample.