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Mutations of forkhead box p3 (FOXP3), the master gene for naturally occurring regulatory T cells (nTregs), are responsible for the impaired function of nTregs, resulting in an autoimmune disease known as the immune dysregulation, polyendocrinopathy, enteropathy, X-linked (IPEX) syndrome. The relevance of other peripheral tolerance mechanisms, such as the presence and function of type 1 regulatory T (Tr1) cells, the major adaptive IL-10-producing Treg subset, in patients with IPEX syndrome remains to be clarified. FOXP3(mutated) Tr1-polarized cells, differentiated in vitro from CD4(+) T cells of four IPEX patients, were enriched in IL-10 1 IL-4(+) IFN-gamma(+) T cells, a cytokine production profile specific for Tr1 cells, and expressed low levels of FOXP3 and high levels of Granzyme-B. IPEX Tr1 cells were hypoproliferative and suppressive, thus indicating that FOXP3 mutations did not impair their function. Furthermore, we isolated Tr1 cell clones from the peripheral blood of one FOXP3(null) patient, demonstrating that Tr1 cells are present in vivo and they can be expanded in vitro in the absence of WT FOXP3. Overall, our results (i) show that functional Tr1 cells differentiate independently of FOXP3, (ii) confirm that human Tr1 and nTregs are distinct T-cell lineages, and (iii) suggest that under favorable conditions Tr1 cells could exert regulatory functions in IPEX patients.

Forkhead box P3 (FOXP3) is constitutively expressed by CD4+CD25hi regulatory T cells (nTregs). Mutations of FOXP3 cause a severe autoimmune syndrome known as immune dysregulation polyendocrinopathy enteropathy X-linked, in which nTregs are absent or dysfunctional. Whether FOXP3 is essential for both differentiation and function of human nTreg cells remains to be demonstrated. Because FOXP3 is an X-linked gene subject to X-chromosome inactivation (XCI), we studied 9 healthy female carriers of FOXP3 mutations to investigate the role of wild-type (WT) versus mutated FOXP3 in different cell subsets. Analysis of active WT versus mutated (mut)–FOXP3 allele distribution revealed a random pattern of XCI in peripheral blood lymphocytes and in naive and memory CD4+T cells, whereas nTregs expressed only the active WT-FOXP3. These data demonstrate that expression of WT-FOXP3 is indispensable for the presence of a normal nTreg compartment and suggest that FOXP3 is not necessary for effector T-cell differentiation in humans.

Immune dysregulation, polyendocrinopathy, enteropathy, X-linked syndrome is a rare X-linked disorder that usually presents in early childhood with immune enteropathy, diabetes mellitus, and other autoimmune complications. The disease is caused by mutations in the forkhead box P3 gene, a transcription factor that is essential for the development and function of regulatory T cells. This population of cells plays an essential role in controlling immune responses and preventing autoimmunity. Immune dysregulation, polyendocrinopathy, enteropathy, X-linked syndrome is often initially treated with immunosuppressive drugs, but only allogeneic hematopoietic stem cell transplantation has offered the possibility of cure. We recently performed an unrelated donor transplant in a child with immune dysregulation, polyendocrinopathy, enteropathy, X-linked syndrome by using a reduced-intensity conditioning regimen. This transplant provided a rare opportunity to gain valuable insight into the regeneration of the immune system after transplantation. Clinical recovery was associated with the emergence of regulatory T cell populations, the majority of which expressed memory phenotype markers and raised important questions about the origin and longevity of the FOXP3+ regulatory T cell pool.

A total of 137 fragile X and 235 control chromosomes from various regions of Italy were haplotyped by analyzing two neighbouring marker microsatellites, FRAXAC1 and DXS548. The number of CGG repeats at the 5{prime} end of the FMR1 gene was also assessed in 141 control chromosomes and correlated with their haplotypes. Significant linkage disequilibrium between some {open_quotes}major{close_quotes} haplotypes and fragile X was observed, while other {open_quotes}minor{close_quotes} haplotypes may have originated by subsequent mutation at the marker microsatellite loci and/or recombination between them. Recent evidence suggests that the initial mechanism leading to CGG instability might consist of rare (10{sup -6/-7}) CGG repeat slippage events and/or loss of a stabilizing AGG via A-to-C transversion. Also, the apparently high variety of fragile X chromosomes may be partly due to the relatively high mutation rate (10{sup -4/-5}) of the microsatellite markers used in haplotyping. Our fragile X sample also showed a higher than expected heterozygosity when compared to the control sample and we suggest that this might be explained by the chance occurrence of the few founding events on different chromosomes, irrespective of their actual frequency in the population. Alternatively, a local mechanism could enhance the microsatellite mutation rate only on fragile X chromosomes,more » or fragile X mutations might occur more frequently on certain background haplotypes. 59 refs., 4 figs.« less

Most common inherited form of intellectual disability, fragile X syndrome is associated to an expansion of greater than 200 CGG repeats in the 5′ untranslated region of the FMR1 gene on the X chromosome which causes transcriptional silencing and deficiency of the encoded protein FMRP. Molecular diagnosis is performed through a combination of PCR to identify fewer than 100–150 repeats and of Southern blot analysis to identify longer alleles and the methylation status of the FMR1 promoter. We present a family with one patient with mild mental retardation who showed an atypical profile at Southern analysis due to the -413C > G transversion located in the FMR1 promoter which had been described as possibly associated with mental retardation. We demonstrated this variant in other four family members along three generations, including the maternal grandfather who did not manifest any pathological feature. Though the -413C > G substitution was not found in a large control series, these findings allowed to exclude its role in determining the disease phenotype.

BACKGROUND: Immune dysregulation, polyendocrinopathy, enteropathy, X-linked (IPEX) syndrome is an autoimmune genetic disorder caused by mutation of the forkhead box protein 3 gene (FOXP3), a key regulator of immune tolerance. OBJECTIVE: We sought to provide clinical and molecular indicators that facilitate the understanding and diagnosis of IPEX syndrome. METHODS: In 14 unrelated affected male subjects who were given diagnoses of IPEX syndrome based on FOXP3 gene sequencing, we determined whether particular FOXP3 mutations affected FOXP3 protein expression and correlated the molecular and clinical data. RESULTS: Molecular analysis of FOXP3 in the 14 subjects revealed 13 missense and splice-site mutations, including 7 novel mutations. Enteropathy, generally associated with endocrinopathy and eczema, was reported in all patients, particularly in those carrying mutations within FOXP3 functional domains or mutations that altered protein expression. However, similar genotypes did not always result in similar phenotypes in terms of disease presentation and severity. In addition, FOXP3 protein expression did not correlate with disease severity. CONCLUSION: Severe autoimmune enteropathy, which is often associated with increased IgE levels and eosinophilia, is the most prominent early manifestation of IPEX syndrome. Nevertheless, the disease course is variable and somewhat unpredictable. Therefore genetic analysis of FOXP3 should always be performed to ensure an accurate diagnosis, and FOXP3 protein expression analysis should not be the only diagnostic tool for IPEX syndrome. OI RONCAROLO, Maria Grazia/0000-0002-2193-9186 ZS 1 ZR 2 ZB 47 Z8 7

Background & Aims: The syndrome of immunodysregulation, polyendocrinopathy, enteropathy, X-linked (IPEX) is a rare disorder resulting in the expression of multiple autoimmune and allergic features. Early onset enteropathy and type 1 diabetes (T1D) are the most common clinical features. The IPEX syndrome is caused by mutations of the FOXP3 gene, which is essential for the development of regulatory T cells (Treg). We describe 2 unrelated patients with IPEX syndrome with a mild clinical phenotype and with novel FOXP3 mutations and the phenotypic and functional characterization of their Treg cells. Methods: The FOXP3 gene was analyzed by sequencing amplimers from genomic DNA. Treg cells were characterized by evaluating the number of CD4+CD25+ T cells and their functional ability to suppress the proliferation of autologous CD4+CD25− effector T cells stimulated with anti-CD3 and anti-CD28 antibodies. Results: A 7-year-old boy and a 24-year-old man presented with autoimmune enteropathy characterized by early onset persistent diarrhea not associated with T1D or other endocrinopathies. These 2 patients carry novel FOXP3 mutations that do not abrogate the function of the forkhead domain. They have normal numbers of CD4+CD25+ T lymphocytes, however, these show severely defective suppressive function in vitro. Conclusions: Our 2 patients show that IPEX patients may present with early onset enteropathy and long-term survival without T1D or other endocrinopathies. This milder phenotype may be associated with FOXP3 mutations that do not abrogate the function of the forkhead domain.

The autoimmune disease immune dysregulation, polyendocrinopathy, enteropathy, X-linked (IPEX) is caused by mutations in the forkhead box protein P3 (FOXP3) gene. In the mouse model of FOXP3 deficiency, the lack of CD4(+)CD25(+) Tregs is responsible for lethal autoimmunity, indicating that FOXP3 is required for the differentiation of this Treg subset. We show that the number and phenotype of CD4(+)CD25(+) T cells from IPEX patients are comparable to those of normal donors. CD4(+)CD25(high) T cells from IPEX patients who express FOXP3 protein suppressed the in vitro proliferation of effector T cells from normal donors, when activated by "weak" TCR stimuli. In contrast, the suppressive function of CD4(+)CD25(high) T cells from IPEX patients who do not express FOXP3 protein was profoundly impaired. Importantly, CD4(+)CD25(high) T cells from either FOXP3(+) or FOXP3(-) IPEX patients showed altered suppression toward autologous effector T cells. Interestingly, IL-2 and IFN-gamma production by PBMCs from IPEX patients was significantly decreased. These findings indicate that FOXP3 mutations in IPEX patients result in heterogeneous biological abnormalities, leading not necessarily to a lack of differentiation of CD4(+)CD25(high) Tregs but rather to a dysfunction in these cells and in effector T cells.

This report complements a series of clinical, cytogenetical, and psychological studies previously reported on a large Sardinian pedigree segregating for premutations and full mutations associated with the Martin-Bell syndrome (MBS). Using the StB12.3 probe, we report now the molecular classification of all of the critical members of the pedigree. These molecular findings are evaluated against the variable phenotypic manifestations of the disease in the course of a six-generation segregation of an MBS premutation allegedly present in a common female progenitor of 14 MBS male patients and 9 female MBS heterozygotes seen in the last two generations. The nature and stepwise progression of MBS-premutations toward the fully manifested Martin-Bell syndrome and the possibility of reverse mutational events toward the normal allele are discussed with respect to the application of the presently available diagnostic tools in genetic counselling.

The precise origin of the supernumerary chromosome can be defined in the majority of trisomy 21 cases. This is achieved by evaluating the chromosome 21 short arm polymorphism and analysing restriction fragment length polymorphisms (RFLPs) of multiple chromosome 21 loci. We report a study on 37 Italian families with Down's syndrome. In 35 cases (94.6%) both the parental and the meiotic stage of non-disjunction could be established. Knowledge of the origin of the extra chromosome 21 is a pre-requisite for investigations of genetic or environmental factors that may affect the meiotic process.

The hypothesis of a predisposition to meiotic nondisjunction for chromosome 21 carrying a specific molecular haplotype has been tested. The haplotype in question is defined by the restriction fragment length polymorphisms for the D21S1/D21S11 loci. Our results obtained on a sample of Northern Italian families with the occurrence of trisomy 21 (Down syndrome) failed to support this hypothesis, contradicting a previous study [Antonarakis, S. E., Kittur, S. D., Metaxotou, C., Watkins, P. C. & Patel, A. S. (1985) Proc. Natl. Acad. Sci. USA 82, 3360-3364]. These findings rule out an association between any specific D21S1/D21S11 haplotype (as well as other haplotypes for the D21S13, ETS2, and D21S23 loci) and a putative cis-acting genetic element favoring the meiotic missegregation of chromosome 21. For this reason, no preventive screening for couples at risk for trisomy 21 may be based on any of the haplotypes tested.