Major Histocompatibility Complex Class II Deficiency due to a Novel Mutation in RFXANK in a Child of Mexican Descent.
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ABSTRACT:
SUBMITTER: Clarridge K
PROVIDER: S-EPMC4720537 | biostudies-literature | 2016 Jan
REPOSITORIES: biostudies-literature
Publications
Major Histocompatibility Complex Class II Deficiency due to a Novel Mutation in RFXANK in a Child of Mexican Descent.
Clarridge Katherine K Leitenberg David D Loechelt Brett B Picard Capuchine C Keller Michael M
Journal of clinical immunology 20151203 1
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Project description:The transcription factors RFX and CIITA are major players in regulation of the expression of all classical and nonclassical major histocompatibility complex class II (MHC-II) genes. RFX nucleates the formation of a multiprotein complex, called the MHC-II enhanceosome, on MHC-II promoters. Assembly of this enhanceosome is an obligatory step for recruitment of the coactivator CIITA and thus for activation of MHC-II gene transcription. We have analyzed the function of the ankyrin repeat-containing protein RFXANK, which forms the heterotrimeric RFX complex together with RFX5 and RFXAP. We discovered that ANKRA2, the closest paralogue of RFXANK, can substitute for RFXANK in the activation of MHC-II genes and that this ability is mediated by its ankyrin repeat domain (ARD). This finding provided the basis for a high-resolution structure-function analysis of the ARD of RFXANK, which allowed us to map the RFX5 interaction domain and residues critical for assembly of the RFX complex. We also found that mutations in the fourth ankyrin repeat of RFXANK abolish assembly of the enhanceosome on MHC-II promoters in vivo but not in vitro, suggesting a new role of RFXANK in facilitating promoter occupation in the context of chromatin.
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Project description:Major histocompatibility complex (MHC) II deficiency is a rare primary immunodeficiency disorder that is characterized by the deficiency of MHC class II molecules. The disease is caused by transcription factor mutations including class II transactivator (CIITA), regulatory factor X-5 (RFX5), RFX-associated protein (RFXAP), and RFXAP-containing ankyrin repeat (RFXANK), respectively. Mutations in the RFXANK gene account for >70% of all known patients worldwide. Herein, we reported a 10-month-old boy with MHC II deficiency caused by a novel mutation in the RFXANK gene (c.337 + 1G>C). The boy was admitted to the hospital due to pneumonia and diarrhea at 4 months of age. Genetic analysis revealed a novel homozygous mutation in the RFXANK gene, which derived from the c.337 + 1G>C heterozygous mutations in the RFXANK gene of his parents. The boy died 3 months after diagnosis. More than 200 cases have been reported, and a review of the literature revealed different mutation rates of 4 transcription factors in different countries or regions. This is the first case report of MHC II deficiency from East Asia. We also describe all gene mutations that cause MHC II deficiency and the epidemiology of MHC II deficiency with gene mutations in this paper.
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Project description:amphibian MHC IIB1 Raw sequence reads
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Project description:PurposeMajor histocompatibility complex (MHC) class II deficiency is one of the combined immune deficiency disorders caused by defects in the MHC class II regulatory genes leading to abnormal T cells development and function. Therefore, patients mainly present with increased susceptibility to infections, diarrhea, and failure to thrive. In this report, we present one MHC class II deficient patient with a novel presentation with Hemophagocytic Lymphohistiocytosis (HLH).MethodsImmunophenotyping of lymphocyte subpopulations and HLA-DR expression was assess by flow cytometry. Gene mutational analysis was performed by whole exome and Sanger sequencing.ResultsWe reported a 7-year-old girl, who was diagnosed at age of 2 years with MHC class II deficiency by genetic testing and flow cytometry. Two years later, she developed disseminated BCGitis which was treated with proper antimicrobial agents. At the age of 7 years, she presented with clinical features fulfilling 6 diagnostic criteria of HLH including evidence of hemophagocytic activity in bone marrow aspiration. Accordingly, the diagnosis of HLH was established and the patient was started on IV Dexamethasone, Anakinra and IVIG. Eventually, patient started to improve and was discharged in good condition. Few months later, the patient was readmitted with severe pneumonia and sepsis leading to death.ConclusionPatients with MHC class II deficiency might present with disseminated BCGitis especially if the patient has severe T cell lymphopenia. Additionally, this immune defect might be added to the list of inborn errors of immunity that can be complicated with HLH.
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Project description:Presenting processed antigens to CD4+ lymphocytes during the immune response involves major histocompatibility complex class II molecules. MHC class II genes transcription is regulated by four transcription factors: CIITA, RFXANK, RFX5 and RFXAP. Defects in these factors result in major histocompatibility complex class II expression deficiency, a primary combined immunodeficiency frequent in North Africa. Autosomal recessive mutations in the RFXANK gene have been reported as being the principal defect found in North African patients with this disorder. In this paper, we describe clinical, immunological and genetic features of 11 unrelated Algerian patients whose monocytes display a total absence of MHC class II molecules. They shared mainly the same clinical picture which included protracted diarrhoea and respiratory tract recurrent infections. Genetic analysis revealed that 9 of the 11 patients had the same RFXANK founder mutation, a 26 bp deletion (named I5E6-25_I5E6+1, also known as 752delG26). Immunological and genetic findings in our series may facilitate genetic counselling implementation for Algerian consanguineous families. Further studies need to be conducted to determine 752delG26 heterozygous mutation frequency in Algerian population.
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