Gastroenterology

Gastroenterology

Volume 132, Issue 5, May 2007, Pages 1705-1717
Gastroenterology

Clinical–alimentary tract
Severe Food Allergy as a Variant of IPEX Syndrome Caused by a Deletion in a Noncoding Region of the FOXP3 Gene

https://doi.org/10.1053/j.gastro.2007.02.044Get rights and content

Background & Aims: Immune dysregulation, polyendocrinopathy, enteropathy, X-linked (IPEX; OMIM 304930) syndrome is a congenital syndrome characterized by autoimmune enteropathy, endocrinopathy, dermatitis, and other autoimmune phenomena. In the present work, we aimed to uncover the molecular basis of a distinct form of IPEX syndrome presenting at the edge of autoimmunity and severe allergy. Methods: The FOXP3 gene was sequenced, FOXP3 messenger RNA (mRNA) was quantified by real-time polymerase chain reaction (PCR), and protein expression in peripheral blood lymphocytes was analyzed by flow cytometry after intracellular staining. In coculture experiments (CD4+CD25 and CD4+CD25+ cells), the functions of regulatory T cells were analyzed. Expression of interferon γ and interleukin 2 and 4 mRNA within the inflamed intestinal mucosa was quantified by real-time PCR. Results: Here, we describe a distinct familial form of IPEX syndrome that combines autoimmune and allergic manifestations including severe enteropathy, food allergies, atopic dermatitis, hyper-IgE, and eosinophilia. We have identified a 1388-base pair deletion (g.del−6247_−4859) of the FOXP3 gene encompassing a portion of an upstream noncoding exon (exon −1) and the adjacent intron (intron −1). This deletion impairs mRNA splicing, resulting in accumulation of unspliced pre-mRNA and alternatively spliced mRNA. This causes low FOXP3 mRNA levels and markedly decreased protein expression in peripheral blood lymphocytes of affected patients. Numbers of CD4+CD25+FOXP3+ regulatory T cells are extremely low, and the CD4+CD25+ T cells that are present exhibit little regulatory function. Conclusions: A new mutation within an upstream noncoding region of FOXP3 results in a variant of IPEX syndrome associating autoimmune and severe immunoallergic symptoms.

Section snippets

Patients IV.1 and IV.2

Patient IV.1, (Figure 1) the index case, followed at Necker-Enfants Malades Hospital, Paris, was born in 2000 after an uneventful pregnancy to unrelated, healthy white parents. No abnormalities were observed during the neonatal period while he was exclusively breastfed. At 3 weeks of age, infant formula was introduced, and, within 1 week, he developed massive watery-bloody diarrhea requiring total parenteral nutrition, daily albumin supplementation, and repeated blood transfusions. The severe

Isolation of Peripheral Blood Mononuclear Cells

Peripheral blood mononuclear cells (PBMC) were isolated from whole blood using Ficoll-Paque gradient centrifugation as previously described.5

Sequence Analysis of FOXP3

Genomic DNA (gDNA) was isolated from whole blood using the QIAamp DNA Blood Mini Kit (Qiagen, Valencia, CA) according to the manufacturer’s protocol. Each of the 11 coding exons of FOXP3 including intron/exon boundaries and the region surrounding the first polyadenylation signal were amplified from gDNA by polymerase chain reaction (PCR) using intronic

Genetic Analysis

The human FOXP3 gene consists of 11 protein-coding exons (exons 1–11) as well as a noncoding exon (exon −1) located 6 kilobases (kb) upstream of exon 1 (Figure 3). All mutations of the FOXP3 gene identified to date are located within, or adjacent to, one of the 11 translated exons or within the first polyadenylation site. Based on the clinical phenotype observed in affected members of this family, we sequenced exons 1–11 of the FOXP3 gene, including all intron/exon boundaries and the first

Discussion

The family reported here presented with an atypical form of IPEX syndrome that was characterized by multiple severe food allergies associated with AIE. The patients also had eczema, hyper-IgE, and eosinophilia but, unlike most other cases of IPEX syndrome, did not present with endocrinopathy or cytopenia. The restricted symptomatology observed in the affected members of this family demonstrates the clinical heterogeneity of the IPEX syndrome and expands the range of patients for whom IPEX

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    Supported by NIH grants HD37091 (to H.D.O.) and HD043376-03 (to T.R.T.), Jeffrey Modell Foundation grant (to H.D.O.), Immunodeficiency Foundation grant (to H.D.O.), INSERM and the Association Francois Aupetit grants (to F.R.), and by a scholarship of the European Leonardo da Vinci Foundation (to N.M.).

    Conflict of interest statement: The authors declare no conflicts of interest.

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