Functional type 1 regulatory T cells develop regardless of FOXP3 mutations in patients with IPEX syndrome.

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(+) IL-4(-) IFN-γ(+) 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.

The refinement of the critical region for the 2q31.2q32.3 deletion syndrome indicates candidate genes for mental retardation and speech impairment.

Current literature provides more than 30 patients with interstitial deletions in chromosome 2q31q33. Only a few of them were studied using high-resolution methods. Among these, two patients had presented with a particular consistence of some clinical features associated to a deletion between bands q31.2 and q32.3 of chromosome 2. This clinical pattern, labeled as "2q31.2q32.3 syndrome," consists of multiple dysmorphisms, developmental delay, mental retardation and behavioural disturbances. We report an adult female patient with a 4.4 Mb deletion in the 2q31.2q32.3 region, showing facial dysmorphisms, mental retardation and absence of speech. The region overlaps with the deletion found in the two cases previously reported. The critical region points to a few genes, namely NEUROD1, ZNF804A, PDE1A, and ITGA4, which are good candidates to explain the cognitive and behavioural phenotype, as well as the severe speech impairment associated with the 2q31.2q32.3 deletion.

The H1 haplotype of the tau gene (MAPT) is associated with mild cognitive impairment.

Mild cognitive impairment is often considered a transitional condition prodromal to Alzheimer's disease. The dissection of genetic risk factors predisposing to mild cognitive impairment is paramount to assess the individual predisposition and reliably evaluate the effectiveness of early therapeutic interventions. We designed a cross-sectional analysis to test whether the occurrence of mild cognitive impairment is influenced by variations of the tau protein gene. The genotypes of seven polymorphisms tagging the major tau haplotypes were assayed on 186 patients with amnestic mild cognitive impairment and 191 unrelated controls. Association study was conducted by logistic regression including APOE genotype and age as covariates. Case-control analysis showed that the common H1 haplotype is significantly overrepresented in patients (OR, 95% CI: 2.31, 1.52-3.51; p<0.001), whereas did not provide positive signals for any of the H1 sub-haplotypes that had been described as associated with Alzheimer inverted exclamation mark s disease. This finding was confirmed when the epsilon4 allele of the APOE gene was taken into account (OR, 95% CI: 2.319, 1.492-3.603; p<0.001). These results firstly suggest that the risk of mild cognitive impairment is influenced by tau protein gene variations and that mild cognitive impairment shares a common genetic background with Alzheimer's disease. They may help elucidating the genetic risk to cognitive decline and designing effective clinical trials.

The -413C > G substitution in the promoter of the FMR1 gene is not associated with the fragile X syndrome phenotype.

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.

Wild-type FOXP3 is selectively active in CD4+CD25(hi) regulatory T cells of healthy female carriers of different FOXP3 mutations.

Forkhead box P3 (FOXP3) is constitutively expressed by CD4(+)CD25(hi) 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.

Clinical and molecular profile of a new series of patients with immune dysregulation, polyendocrinopathy, enteropathy, X-linked syndrome: inconsistent correlation between forkhead box protein 3 expression and disease severity.

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.

Immune reconstitution and recovery of FOXP3 (forkhead box P3)-expressing T cells after transplantation for IPEX (immune dysregulation, polyendocrinopathy, enteropathy, X-linked) syndrome.

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.

Defective regulatory and effector T cell functions in patients with FOXP3 mutations.

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+ CD25high 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+ CD25high T cells from IPEX patients who do not express FOXP3 protein was profoundly impaired. Importantly, CD4+ CD25high 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+ CD25high Tregs but rather to a dysfunction in these cells and in effector T cells.

Mechanistic associations of a mild phenotype of immunodysregulation, polyendocrinopathy, enteropathy, x-linked syndrome.

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.

Successful use of the new immune-suppressor sirolimus in IPEX (immune dysregulation, polyendocrinopathy, enteropathy, X-linked syndrome).

IPEX (immune-dysregulation, polyendocrinopathy, enteropathy, X-linked) syndrome is an autoimmune disorder with an often lethal outcome in spite of immunosuppressive therapy. We report the successful use of sirolimus in 3 patients with IPEX. The efficacy of sirolimus is probably due to its different mode of action compared to calcineurin-dependent agents.