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Somatic mutations in lymphocytes in patients with immune-mediated aplastic anemia.

ABSTRACT: The prevalence and functional impact of somatic mutations in nonleukemic T cells is not well characterized, although clonal T-cell expansions are common. In immune-mediated aplastic anemia (AA), cytotoxic T-cell expansions are shown to participate in disease pathogenesis. We investigated the mutation profiles of T cells in AA by a custom panel of 2533 genes. We sequenced CD4+ and CD8+ T cells of 24 AA patients and compared the results to 20 healthy controls and whole-exome sequencing of 37 patients with AA. Somatic variants were common both in patients and healthy controls but enriched to AA patients' CD8+ T cells, which accumulated most mutations on JAK-STAT and MAPK pathways. Mutation burden was associated with CD8+ T-cell clonality, assessed by T-cell receptor beta sequencing. To understand the effect of mutations, we performed single-cell sequencing of AA patients carrying STAT3 or other mutations in CD8+ T cells. STAT3 mutated clone was cytotoxic, clearly distinguishable from other CD8+ T cells, and attenuated by successful immunosuppressive treatment. Our results suggest that somatic mutations in T cells are common, associate with clonality, and can alter T-cell phenotype, warranting further investigation of their role in the pathogenesis of AA.

SUBMITTER: Lundgren S

PROVIDER: S-EPMC8102188 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Somatic mutations in lymphocytes in patients with immune-mediated aplastic anemia

Project description:In this study, we investigated somatic mutations of CD4+ and CD8+ T cells in patients with immune-mediated aplastic anemia (AA). To understand the role of mutations, we performed single-cell level analysis of 6 longitudinal samples of 2 AA patients carrying STAT3 or KRAS and other mutations in CD8+ T cells. The analysis was performed using V(D)J and 5' gene expression platform (10X Genomics). STAT3 mutated clone was clearly distinguishable from other CD8+ T cells and showed a cytotoxic phenotype, attenuated by successful immunosuppressive treatment. Our results suggest that somatic mutations in T cells can alter T cell phenotype warranting further investigation of their role in the pathogenesis of immune-mediated AA.

2021-03-24 | E-MTAB-9969 | biostudies-arrayexpress

Somatic mutations in lymphocytes in patients with immune-mediated aplastic anemia

| EGAS00001004994 | EGA

Somatic Mutations and Clonal Hematopoiesis in Aplastic Anemia.

Project description:BACKGROUND:In patients with acquired aplastic anemia, destruction of hematopoietic cells by the immune system leads to pancytopenia. Patients have a response to immunosuppressive therapy, but myelodysplastic syndromes and acute myeloid leukemia develop in about 15% of the patients, usually many months to years after the diagnosis of aplastic anemia. METHODS:We performed next-generation sequencing and array-based karyotyping using 668 blood samples obtained from 439 patients with aplastic anemia. We analyzed serial samples obtained from 82 patients. RESULTS:Somatic mutations in myeloid cancer candidate genes were present in one third of the patients, in a limited number of genes and at low initial variant allele frequency. Clonal hematopoiesis was detected in 47% of the patients, most frequently as acquired mutations. The prevalence of the mutations increased with age, and mutations had an age-related signature. DNMT3A-mutated and ASXL1-mutated clones tended to increase in size over time; the size of BCOR- and BCORL1-mutated and PIGA-mutated clones decreased or remained stable. Mutations in PIGA and BCOR and BCORL1 correlated with a better response to immunosuppressive therapy and longer and a higher rate of overall and progression-free survival; mutations in a subgroup of genes that included DNMT3A and ASXL1 were associated with worse outcomes. However, clonal dynamics were highly variable and might not necessarily have predicted the response to therapy and long-term survival among individual patients. CONCLUSIONS:Clonal hematopoiesis was prevalent in aplastic anemia. Some mutations were related to clinical outcomes. A highly biased set of mutations is evidence of Darwinian selection in the failed bone marrow environment. The pattern of somatic clones in individual patients over time was variable and frequently unpredictable. (Funded by Grant-in-Aid for Scientific Research and others.).

| S-EPMC7478337 | biostudies-literature

Perforin gene mutations in patients with acquired aplastic anemia.

Project description:Perforin is a cytolytic protein expressed mainly in activated cytotoxic lymphocytes and natural killer cells. Inherited perforin mutations account for 20% to 40% of familial hemophagocytic lymphohistiocytosis, a fatal disease of early childhood characterized by the absence of functional perforin. Aplastic anemia, the paradigm of immune-mediated bone marrow failure syndromes, is characterized by hematopoietic stem cell destruction by activated T cells and Th1 cytokines. We examined whether mutations in the perforin gene occurred in acquired aplastic anemia. Three nonsynonymous PRF1 mutations among 5 unrelated patients were observed. Four of 5 patients with the mutations showed some hemophagocytosis in the bone marrow at diagnosis. Perforin protein levels in these patients were very low or absent, and perforin granules were completely absent. Natural killer (NK) cell cytotoxicity from these patients was significantly decreased. Our data suggest that PRF1 genetic alterations help explain the aberrant proliferation and activation of cytotoxic T cells and may represent genetic risk factors for bone marrow failure.

| S-EPMC1890825 | biostudies-other

Somatic HLA Mutations Expose the Role of Class I-Mediated Autoimmunity in Aplastic Anemia and its Clonal Complications.

Project description:Acquired aplastic anemia (aAA) is an acquired deficiency of early hematopoietic cells, characterized by inadequate blood production, and a predisposition to myelodysplastic syndrome (MDS) and leukemia. Although its exact pathogenesis is unknown, aAA is thought to be driven by Human Leukocyte Antigen (HLA)-restricted T cell immunity, with earlier studies favoring HLA class II-mediated pathways. Using whole exome sequencing (WES), we recently identified two aAA patients with somatic mutations in HLA class I genes. We hypothesized that HLA class I mutations are pathognomonic for autoimmunity in aAA, but were previously underappreciated because the Major Histocompatibility Complex (MHC) region is notoriously difficult to analyze by WES. Using a combination of targeted deep sequencing of HLA class I genes and single nucleotide polymorphism array (SNP-A) genotyping we screened 66 aAA patients for somatic HLA class I loss. We found somatic HLA loss in eleven patients (17%), with thirteen loss-of-function mutations in HLA-A*33:03, HLA-A*68:01, HLA-B*14:02 and HLA-B*40:02 alleles. Three patients had more than one mutation targeting the same HLA allele. Interestingly, HLA-B*14:02 and HLA-B*40:02 were significantly overrepresented in aAA patients, compared to ethnicity-matched controls. Patients who inherited the targeted HLA alleles, regardless of HLA mutation status, had a more severe disease course with more frequent clonal complications as assessed by WES, SNP-A, and metaphase cytogenetics, and more frequent secondary MDS. The finding of recurrent HLA class I mutations provides compelling evidence for a predominant HLA class I-driven autoimmunity in aAA, and establishes a novel link between aAA patients' immunogenetics and clonal evolution.

| S-EPMC5621748 | biostudies-literature

(Auto-)immune signature in aplastic anemia.

Project description: Not available

| S-EPMC5927975 | biostudies-literature

Mutations of ASXL1 and TET2 in aplastic anemia.

Project description: Not available

| S-EPMC4420224 | biostudies-literature

Therapeutic targeting of NOTCH signaling ameliorates immune-mediated bone marrow failure of aplastic anemia.

Project description:Severe aplastic anemia (AA) is a bone marrow (BM) failure (BMF) disease frequently caused by aberrant immune destruction of blood progenitors. Although a Th1-mediated pathology is well described for AA, molecular mechanisms driving disease progression remain ill defined. The NOTCH signaling pathway mediates Th1 cell differentiation in the presence of polarizing cytokines, an action requiring enzymatic processing of NOTCH receptors by ?-secretase. Using a mouse model of AA, we demonstrate that expression of both intracellular NOTCH1(IC) and T-BET, a key transcription factor regulating Th1 cell differentiation, was increased in spleen and BM-infiltrating T cells during active disease. Conditionally deleting Notch1 or administering ?-secretase inhibitors (GSIs) in vivo attenuated disease and rescued mice from lethal BMF. In peripheral T cells from patients with untreated AA, NOTCH1(IC) was significantly elevated and bound to the TBX21 promoter, showing NOTCH1 directly regulates the gene encoding T-BET. Treating patient cells with GSIs in vitro lowered NOTCH1(IC) levels, decreased NOTCH1 detectable at the TBX21 promoter, and decreased T-BET expression, indicating that NOTCH1 signaling is responsive to GSIs during active disease. Collectively, these results identify NOTCH signaling as a primary driver of Th1-mediated pathogenesis in AA and may represent a novel target for therapeutic intervention.

| S-EPMC3698520 | biostudies-literature

Mutations in the SBDS gene in acquired aplastic anemia.

Project description:Shwachman-Diamond syndrome (SDS; OMIM 260400), an inherited bone marrow failure syndrome, is caused by mutations in both alleles of the SBDS gene, which encodes a protein of unknown function. Here we report heterozygosity for the 258 + 2 T>C SBDS gene mutation previously identified in SDS patients in 4 of 91 patients with apparently acquired aplastic anemia (AA) but not in 276 ethnically matched controls (Fisher exact test, P < .004). Affected patients were young and had a poor outcome; they had reduced SBDS expression but no evidence of the pancreatic exocrine failure or skeletal abnormalities typical of SDS. Length of telomeres in granulocytes of SBDS heterozygous patients was short for their age, and in SDS patients with both SBDS alleles affected further analyzed, granulocytes' telomeres were even shorter, correlating in length with SBDS expression. Higher heterogeneity in telomere length also was observed in SDS patients. Telomerase activity of SBDS-deficient patients' lymphocytes was comparable with controls, and no physical interaction between SBDS protein and telomerase complex components (TERT or TERC) was established. We propose that heterozygosity for the 258 + 2 T>C SBDS mutation predisposes to AA by accelerating telomere shortening of leukocytes via a telomerase-independent mechanism.

| S-EPMC1939897 | biostudies-literature

Th17 immune responses contribute to the pathophysiology of aplastic anemia.

Project description:T helper type 17 (Th17) cells have been characterized based on production of interleukin-17 (IL-17) and association with autoimmune diseases. We studied the role of Th17 cells in aplastic anemia (AA) by isolating Th17 cells from patients blood (n = 41) and bone marrow (BM) mononuclear cells (n = 7). The frequency and total number of CD3(+)CD4(+)IL-17-producing T cells were increased in AA patients at presentation compared with healthy controls (P = .0007 and .02, respectively) and correlated with disease activity. There was an inverse relationship between the numbers of Th17 cells and CD4(+)CD25(high)FoxP3(+) regulatory T cells (Tregs) in the blood of AA patients. Concomitant with the classical Th1 response, we detected the presence of CD4(+) and CD8(+) IL-17-producing T cells in a mouse model of lymph node infusion-induced BM failure. Although anti-IL-17 treatment did not abrogate BM failure, early treatment with the anti-IL-17 antibody reduced the severity of BM failure with significantly higher platelet (P < .01) and total BM cell (P < .05) counts at day 10. Recipients that received anti-IL-17 treatment had significantly fewer Th1 cells (P < .01) and more Treg cells (P < .05) at day 10 after lymph node infusion. Th17 immune responses contribute to AA pathophysiology, especially at the early stage during disease progression.

| S-EPMC2993623 | biostudies-literature

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