Molecular Mechanisms Of The Autoimmune Lymphoproliferative Syndrome

自身免疫性淋巴增殖综合征的分子机制

• 批准号: 8946324
• 负责人: michael j lenardo
• 金额: $ 55.78万
• 依托单位: NATIONAL INSTITUTE OF ALLERGY AND INFECTIOUS DISEASES
• 依托单位国家: 美国
• 资助国家: 美国
• 起止时间: 至
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/8946324
• 关键词: Adaptor Signaling Protein; Adrenal Cortex Hormones; Affect; Age; Amino Acids; Apoptosis; Atypical lymphocyte; Autoimmune Process; Autoimmunity; B-Cell Lymphomas; Biological Markers; Blood; CASP10 gene; CASP8 Gene Mutation; CD8B1 gene; CD95 Antigens; Caspase; Cell Death; Cell Surface Receptors; Cells; Cellular Morphology; Cessation of life; Characteristics; Child; Childhood; Chromosomes; Chronic; Cleaved cell; Clinical; Clinical Protocols; Complement; Complex; Confidence Intervals; Cysteine-Rich Domain; DNA Sequence; Death Domain; Defect; Development; Diabetes Mellitus; Diagnosis; Disease; Elements; Enrollment; Equilibrium; Event; Exons; Failure; Family; Female; Functional disorder; Future; Gene Expression Microarray Analysis; Gene Mutation; Genes; Germ-Line Mutation; Hematopoietic Neoplasms; Hodgkin Disease; Homeostasis; Human; Hypersplenism; Immune; Immune system; Immunologic Deficiency Syndromes; In Vitro; Incidence; Individual; Inherited; KRAS2 gene; Laboratories; Lead; Ligand Binding; Ligands; Light; Lymphatic Diseases; Lymphocyte; Lymphoid; Lymphoma; Malignant Neoplasms; Mediating; Molecular; Molecular Abnormality; Morbidity - disease rate; Multiple Sclerosis; Mutation; Mycophenolate; N-ras Genes; Natural History; Necrosis; Non-Hodgkin' s Lymphoma; Non-Malignant; Organ; Outcome; Patients; Penetrance; Peripheral; Persons; Physiology; Process; Proteins; Protocols documentation; Publishing; Reaction; Recommendation; Relative (related person); Relative Risks; Reporting; Rheumatoid Arthritis; Risk; Role; Sepsis; Serum; Signal Transduction; Sirolimus; Somatic Mutation; Specimen; Splenectomy; Splenomegaly; Surgical complication; Swelling; Symptoms; Syndrome; T-Lymphocyte; TNFRSF6 gene; Techniques; Tissues; Transmembrane Domain; Tumor Necrosis Factor-alpha; United States National Institutes of Health; Vitamin B 12; Withdrawal; apoptosis in lymphocytes; autoimmune lymphoproliferative syndrome; base; caspase-10; caspase-8; clinical phenotype; cohort; comparative genomic hybridization; cytokine; cytopenia; extracellular; follow-up; immunoregulation; improved; insight; lymph nodes; male; mortality; mutant; next generation; programs; protein complex; receptor; research study; response

This project is based on our discovery that genetic mutations in molecules that control the programmed death, or apoptosis, of lymphocytes are responsible for the Autoimmune Lymphoproliferative Syndrome (ALPS). ALPS is a disease affecting children that leads to loss of normal lymphocyte homeostasis leading to swollen lymph glands and organs. Because lymphocytes are the primary cell mediating immune reactions, this excess of lymphocytes leads to a pathological autoimmune attack on the patients own tissues. We have identified mutations in a death-inducing cell surface receptor termed Fas (also known as APO-1 or CD95) and in other molecules that regulate apoptosis. The FAS receptor is homotrimeric and activated by the cognate FAS ligand (FASL), another homotrimeric protein complex homologous to tumor necrosis factor (TNF). Following stimulation, the intracellular death domain (DD) portion of FAS nucleates an extended helical complex of the FADD adaptor protein and caspases-8 and -10. These caspases undergo proteolytic autoprocessing and cleave, in a signaling cascade, downstream effector caspases and other targets leading to the cellular death process of apoptosis. The FAS gene contains 9 exons spanning 26 Kb on chromosome 10q24.118. The first 5 exons encode the extracellular portion containing three cysteine-rich domains that control receptor trimerization and FASL binding. Exon 6 represents the transmembrane domain (TM), and the intracellular portion is encoded by exons 7 through 9. The FAS DD encoded by exon 9 is 85-amino acids long and critical for apoptosis signaling. ALPS-FAS is most frequently caused by heterozygous mutations that generate mutant FAS proteins, often with defective DDs. The defective FAS chains associate with wild-type chains via the pre-ligand assembly domain (PLAD) resulting in functionally defective receptor trimers, a phenomenon termed dominant interference. Less frequently, heterozygous mutations cause decreased FAS protein and haploinsufficiency. Mutations in genes encoding FASL, FADD, and CASP10, also cause ALPS termed ALPS-FASL, ALPS-FADD, and ALPS-CASP10,respectively. Germline mutations in CASP8 or somatic mutations in NRAS and KRAS cause ALPS-related syndromes with distinct clinical phenotypes. Importantly, FAS mutations are associated with in vitro lymphocyte apoptosis defects but may show variable clinical penetrance which has not been fully defined. in a study completed this year, we determined the full clinical, molecular and laboratory assessments of 150 ALPS-FAS patients and 63 healthy mutations positive relatives (HMPRs) to broaden the current understanding of the diagnosis and management of ALPS-FAS. We have found that ALPS presents in childhood with nonmalignant lymphadenopathy and splenomegaly associated with a characteristic expansion of mature CD4 and CD8 negative or double negative TCRalpha/beta+ T cells. Patients often present with chronic multilineage cytopenias due to autoimmune peripheral destruction and/or splenic sequestration of blood elements and have an increased risk of B cell lymphoma. Deleterious heterozygous mutations in the FAS gene are the most common cause of this condition, termed ALPS-FAS. We have determined the natural history and pathophysiology of 150 ALPS-FAS patients and 63 healthy mutation-positive relatives evaluated at the NIH clinical center over the last two decades. Our principal findings are that FAS mutations have a clinical penetrance of less than 60%, elevated serum vitamin B12 is a reliable and accurate biomarker of ALPS-FAS, and the major causes of morbidity and mortality in these patients are the complications of surgical splenectomy and the development of lymphoma. The fact that 41% (27/66) of the splenectomized patients in our cohort had at least one episode of post splenectomy sepsis and 6 of them have died profoundly reinforces the recommendation of avoiding splenectomy and managing chronic cytopenias pharmaceutically. With the long follow up of our study, we observed a significantly greater relative risk of lymphoma than previously reported. We uncovered 18 B cell lymphomas in ALPS-FAS individuals and HMPRs and one non-lymphoid hematopoietic malignancy. The age at diagnosis ranged from 5-60 years (median 17 years). The male to female ratio was 14:5. This included 10 cases of Hodgkins lymphoma in 150 ALPS-FAS patients compared to 0.067 expected giving an observed to expected ratio (O/E) of 149 (95%, confidence interval (CI) = 71 274) and 6 cases of Non-Hodgkin lymphoma compared to 0.099 expected (O/E = 61; 95% CI = 22 132) in ALPS-FAS. The O/E ratios were both highly significant. Standardized incidence ratio (SIR) values are 149 and 61 for Hodgkin and Non-Hodgkin lymphoma, respectively, in the current report versus 51 and 14, respectively, in a previous report we published in 2001. This difference may be related to the cumulative increase of lymphoma with age and accrual of additional events and person-years. Surveillance for lymphoma and avoiding splenectomy while controlling hypersplenism using corticosteroid-sparing treatments such as mycophenolate or sirolimus improves the outcome in ALPS-FAS patients. We are presently studying a class of these patients called ALPS Type III which do not display mutations in the Fas receptor, its ligand (Fas ligand), or caspase-10. We are using a variety of molecular analyses to determine the gene mutation that underlies disease in ALPS Type III. These experiments have been successful in uncovering the molecular basis of a new class of this disease, ALPS type IV. Patients with this disorder have typical clinical features of autoimmunity and abnormal lymphocyte homeostasis that are detected in ALPS, type I and II. however, these patients differ in that they have a strikingly decreased death in response to cytokine withdrawal rather than a defect in death receptor apoptosis. The molecular basis of this disorder is a reduction in the apoptosis protein Bim due to an inherited germline mutation in the N-Ras oncogene. We plan to continue to examine unusual Alps Type III cases to understand their molecular basis. Our guiding principle is that patient specimens from poorly understood diseases can yield valuable insights into disease mechanisms and normal physiology if investigated properly at the molecular level. We have found several new mutations in these unusual patient disorders and are currently characterizing their role in lymphocyte homeostasis and apoptosis.

该项目基于我们的发现，即控制淋巴细胞程序性死亡或凋亡的分子中的基因突变是导致自身免疫性淋巴细胞增生性综合征（ALPS）的原因。ALPS是一种影响儿童的疾病，导致正常淋巴细胞稳态丧失，导致淋巴腺和器官肿大。由于淋巴细胞是介导免疫反应的主要细胞，这种过量的淋巴细胞会导致患者自身组织的病理性自身免疫攻击。我们已经确定了死亡诱导细胞表面受体Fas（也称为APO-1或CD95）和其他调节细胞凋亡的分子中的突变。FAS受体是同源三聚体，由同源FAS配体（FASL）激活，FASL是另一种与肿瘤坏死因子（TNF）同源的三聚体蛋白复合物。刺激后，FAS的细胞内死亡结构域（DD）部分形成FADD接头蛋白和caspase -8和-10的延伸螺旋复合体。这些caspase经过蛋白水解的自动加工和切割，在信号级联中，下游效应caspase和其他靶标导致细胞凋亡的死亡过程。FAS基因在染色体10q24.118上包含9个长26 Kb的外显子。前5个外显子编码细胞外部分，包含三个富含半胱氨酸的结构域，控制受体三聚化和FASL结合。外显子6代表跨膜结构域（TM），细胞内部分由外显子7至9编码。外显子9编码的FAS DD长度为85个氨基酸，对细胞凋亡信号传导至关重要。ALPS-FAS最常由杂合突变引起，产生突变的FAS蛋白，通常具有缺陷的dd。有缺陷的FAS链通过预配体组装域（PLAD）与野生型链结合，导致受体三聚体功能缺陷，这种现象称为显性干扰。不太常见的是，杂合突变导致FAS蛋白减少和单倍体功能不全。编码FASL、FADD和CASP10的基因突变也会导致ALPS，分别称为ALPS-FASL、ALPS-FADD和ALPS-CASP10。CASP8的种系突变或NRAS和KRAS的体细胞突变导致具有不同临床表型的alps相关综合征。重要的是，FAS突变与体外淋巴细胞凋亡缺陷有关，但可能表现出尚未完全确定的可变临床外显率。在今年完成的一项研究中，我们对150名ALPS-FAS患者和63名健康突变阳性亲属（hmpr）进行了全面的临床、分子和实验室评估，以扩大目前对ALPS-FAS诊断和管理的认识。