Abdoreza Davoodi-Semiromi

Characterization of mutations in patients with autoimmune polyglandular syndrome type 1 (APS1)

Abstract Autoimmune polyglandular syndrome type 1 (APS1), also known as autoimmune polyendocrinopathy candidiasis ectodermal dystrophy (APECED), is an autosomal recessive disorder characterized by the failure of several endocrine glands as well as nonendocrine organs. The autoimmune regulator (AIRE) gene responsible for APS1 on chromosome 21q22.3 has recently been identified. Here, we have characterized mutations in the AIRE gene by direct DNA sequencing in 16 unrelated APS1 families ascertained mainly from the USA. Our analyses identified four different mutations (a 13-bp deletion, a 2-bp insertion, one nonsense mutation, and one potential splice/donor site mutation) that are likely to be pathogenic. Fifty-six percent (9/16) of the patients contained at least one copy of a 13-bp deletion (1094–1106del) in exon 8 (seven homozygotes and two compound heterozygotes). A nonsense mutation (R257X) in exon 6 was also found in 31.3% (5/16) of the USA patients. These data are important for genetic diagnosis and counseling for families with autoimmune endocrine syndromes.

Upregulation of Foxp3 expression in mouse and human Treg is IL-2/STAT5 dependent: implications for the NOD STAT5B mutation in diabetes pathogenesis.

Abstract:  Regulatory T cells (Treg), characterized as CD4+/CD25+hi T cells, are critical for sustaining and promoting immune tolerance. Treg are highly dependent on IL‐2 and IL‐2 signaling to maintain their numbers and function and interruption of this pathway promotes autoimmunity. The transcription factor, Foxp3, is also required for Treg function as defective Foxp3 promotos autoimmunity in both mice and humans. We previously reported a point mutation in the DNA‐binding domain of the NOD STAT5B gene that limits DNA binding when compared to wild‐type STAT5 mice. Based on the presence of five STAT5B consensus sequences in the Foxp3 promotor, we hypothesized a critical linkage between IL‐2 signaling/STAT5B and Foxp3 expression in Treg. Our data show IL‐2 activates long‐form (LF) STAT5 and sustains Foxp3 expression in Treg. In contrast, CD4+/CD25− T cells do not active LF STAT5 and do not express Foxp3 under the same conditions. In addition, blocking LF STAT5 activation with a Jak inhibitor (AG‐490) significantly reduced Foxp3 expression in Treg. Examination of human Treg using flow cytometry and intracellular staining for Foxp3 expression likewise demonstrates that IL‐2 maintains Foxp3 expression through LF STAT5 signaling. These studies reveal a critical link between IL‐2 mediated JAK‐STAT5 signaling and the maintenance of Foxp3 expression in Treg of mice and humans.

The tyrphostin agent AG490 prevents and reverses type 1 diabetes in NOD mice.

Background Recent studies in the NOD (non-obese diabetic) mouse model of type 1 diabetes (T1D) support the notion that tyrosine kinase inhibitors have the potential for modulating disease development. However, the therapeutic effects of AG490 on the development of T1D are unknown. Materials and Methods Female NOD mice were treated with AG490 (i.p, 1 mg/mouse) or DMSO starting at either 4 or 8 week of age, for five consecutive week, then once per week for 5 additional week. Analyses for the development and/or reversal of diabetes, insulitis, adoptive transfer, and other mechanistic studies were performed. Results AG490 significantly inhibited the development of T1D (p = 0.02, p = 0.005; at two different time points). Monotherapy of newly diagnosed diabetic NOD mice with AG490 markedly resulted in disease remission in treated animals (n = 23) in comparision to the absolute inability (0%; 0/10, p = 0.003, Log-rank test) of DMSO and sustained eugluycemia was maintained for several months following drug withdrawal. Interestingly, adoptive transfer of splenocytes from AG490 treated NOD mice failed to transfer diabetes to recipient NOD.Scid mice. CD4 T-cells as well as bone marrow derived dendritic cells (BMDCs) from AG490 treated mice, showed higher expression of Foxp3 (p<0.004) and lower expression of co-stimulatory molecules, respectively. Screening of the mouse immune response gene arrary indicates that expression of costimulaotry molecule Ctla4 was upregulated in CD4+ T-cell in NOD mice treated with AG490, suggesting that AG490 is not a negative regulator of the immune system. Conclusion The use of such agents, given their extensive safety profiles, provides a strong foundation for their translation to humans with or at increased risk for the disease.

GM-CSF induces STAT5 binding at epigenetic regulatory sites within the Csf2 promoter of non-obese diabetic (NOD) mouse myeloid cells.

Myeloid cells from non-obese diabetic (NOD) mouse and human type 1 diabetic (T1D) patients overexpress granulocyte-macrophage colony stimulation factor (GM-CSF). This overproduction prolongs the activation of signal transduction and activator of transcription 5 (STAT5) proteins, involved in GM-CSF-induced control of myeloid cell gene expression. We found that GM-CSF can regulate the binding of STAT5 on the promoter of its own gene, Csf2, within regions previously identified as sites of chromatin epigenetic modification important to the regulation of GM-CSF during myeloid differentiation and inflammation. We found multiple sequence polymorphisms within NOD mouse chromosome 11 Idd4.3 diabetes susceptibility region that alter STAT5 GAS binding sequences within the Csf2 promoter. STAT5 binding at these sites in vivo is increased significantly in GM-CSF-stimulated-bone marrow cells and in unactivated, high GM-CSF-producing macrophages from NOD mice as compared to non-autoimmune C57BL/6 mouse myeloid cells. Thus, GM-CSF overproduction by NOD myeloid cells may be perpetuating a positive epigenetic regulatory feedback on its own gene expression through its induction of STAT5 binding to its promoter. These findings suggest that aberrant STAT5 binding at epigenetic regulatory sites may contribute directly to immunopathology through cytokine-induced gene expression dysregulation that can derail myeloid differentiation and increase inflammatory responsiveness.

Aberrant RNA splicing in the hMSH2 gene: Molecular identification of three aberrant RNA in Scottish patients with colorectal cancer in the West of Scotland

Blood samples from 47 unselected patients with colorectal cancer were used as a source of hMSH2 mRNA. We identified three new hMSH2 aberrant mRNAs including: 1) IVS15 +5 G-->C resulting in exon 15 skipping from transcript; 2) an mRNA deletion of exons 2 to 6 inclusive; and 3) an mRNA deletion of exons 2 to 8 inclusive. In order to find out whether or not exon skipping is a natural consequence of alternative mRNA splicing, total RNA from 20 healthy individuals was converted to cDNA by reverse-transcriptase polymerase chain reaction, and our results show that none of the healthy individuals have the above aberrant mRNA. Our results also show that the presence of mutations in colorectal cancer cases, which do not fully meet the hereditary non-polyposis colon cancer criteria, would suggest that all familial cases should be investigated for germ line mutations in the mismatch repair genes.

Csf2 and Ptgs2 Epigenetic Dysregulation in Diabetes-prone Bicongenic B6.NODC11bxC1tb Mice.

In Type 1 diabetic (T1D) human monocytes, STAT5 aberrantly binds to epigenetic regulatory sites of two proinflammatory genes, CSF2 (encoding granulocyte–macrophage colony-stimulating factor) and PTGS2 (encoding prostaglandin synthase 2/cyclooxygenase 2). Bicongenic B6.NOD C11bxC1tb mice re-create this phenotype of T1D monocytes with only two nonobese diabetic (NOD) Idd subloci (130.8 Mb–149.7 Mb, of Idd5 on Chr 1 and 32.08–53.85 Mb of Idd4.3 on Chr11) on C57BL/6 genetic background. These two Idd loci interact through STAT5 binding at upstream regulatory regions affecting Csf2 (Chr 11) and Ptgs2 (Chr 1) expression. B6.NODC11bxC1tb mice exhibited hyperglycemia and immune destruction of pancreatic islets between 8 and 30 weeks of age, with 12%–22% penetrance. Thus, B6.NODC11bxC1tb mice embody NOD epigenetic dysregulation of gene expression in myeloid cells, and this defect appears to be sufficient to impart genetic susceptibility to diabetes in an otherwise genetically nonautoimmune mouse.

Influence of Tyrphostin AG490 on the expression of diabetes-associated markers in human adipocytes

Tyrosine kinase inhibitors (TKi) hold promise as a treatment for a variety of disorders ranging from those in oncology to diseases thought as immune mediated. Tyrphostin AG490 is a potent Jak-Stat TKi shown effective in the prevention of allograft transplant rejection, experimental autoimmune disease, as well as the treatment of cancer. However, given its ability to modulate this important but pleiotropic intracellular pathway, we thought that it is important to examine its effects on glucose metabolism and expression of major transcription factors and adipokines associated with insulin insensitivity and diabetes. We investigated the metabolic effects of AG490 on glucose levels in vivo using an animal model of diabetes, nonobese diabetic (NOD) mice, and transcription factor expression through assessment of human adipocytes. AG490 treatment of young nondiabetic NOD mice significantly reduced blood glucose levels (p = 0.002). In vitro, treatment of adipocytes with rosiglitazone, an insulin sensitizer that binds to peroxisome proliferator-activated receptor (PPAR) receptors and increases the adipocyte response to insulin, significantly increased the expression of the antidiabetic adipokine adiponectin. Importantly, the combination of rosiglitazone plus Tyrphostin AG490 further increased this effect and was specifically associated with significant upregulation of C-enhanced binding protein (C/EBP) (p < 0.0001). In terms of the mechanism underlying this action, regulatory regions of the PPARγ, ADIPOQ, and C/EBP contain the Stat5 DNA-binding sequences and were demonstrated, by gel shift experiments in vitro. These data suggest that blocking Jak-Stat signaling with AG490 reduces blood glucose levels and modulates the expression of transcription factors previously associated with diabetes, thereby supporting its potential as a therapy for this disease.