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Patients with Griscelli syndrome and normal pigmentation identify RAB27A mutations that selectively disrupt MUNC13-4 binding.

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Cetica, Valentina 
Hackmann, Yvonne 
Grieve, Samantha 
Sieni, Elena 
Ciambotti, Benedetta 


BACKGROUND: Familial hemophagocytic lymphohistiocytosis (FHL) is a rare and often fatal disorder characterized by defective cellular cytotoxicity and hyperinflammation, and the only cure known to date is hematopoietic stem cell transplantation. Mutations in RAB27A, LYST, and AP3B1 give rise to FHL associated with oculocutaneous albinism, and patients with FHL are usually only screened for mutations in these genes when albinism is observed. A number of patients with FHL and normal pigmentation remain without a genetic diagnosis. OBJECTIVE: We asked whether patients with FHL with immunodeficiency but with normal pigmentation might sometimes have mutations that affected cellular cytotoxicity without affecting pigmentation. METHODS: We carried out mutation analysis of RAB27A, LYST, and AP3B1 in patients with FHL with pigment dilution, as well as a cohort with no clinical evidence of pigment dilution but no mutations in the other known FHL-related genes (PRF1, STXBP2, and UNC13D). RESULTS: We identify patients with Griscelli syndrome type 2 with biallelic mutations in RAB27A in the absence of albinism. All 6 patients carried mutations at amino acids R141, Y159, or S163 of Rab27a that disrupt the interaction of Rab27a with Munc13-4, without impairing the interaction between melanophilin and Rab27a. CONCLUSION: These studies highlight the need for RAB27A sequencing in patients with FHL with normal pigmentation and identify a critical binding site for Munc13-4 on Rab27a, revealing the molecular basis of this interaction.



Griscelli syndrome type 2, Hemophagocytic lymphohistiocytosis, cytotoxic T lymphocyte, familial hemophagocytic lymphohistiocytosis, melanophilin, natural killer cells, Adaptor Proteins, Signal Transducing, Adolescent, Albinism, Case-Control Studies, Cell Degranulation, Cell Line, Child, Child, Preschool, Cohort Studies, Cytotoxicity, Immunologic, DNA Mutational Analysis, Female, Gene Expression, Genetic Markers, Humans, Infant, Lymphohistiocytosis, Hemophagocytic, Male, Membrane Proteins, Models, Molecular, Mutation, Perforin, Phenotype, Protein Binding, Protein Conformation, Skin Pigmentation, rab GTP-Binding Proteins, rab27 GTP-Binding Proteins

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J Allergy Clin Immunol

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Elsevier BV
Wellcome Trust (100140/Z/12/Z)
Wellcome Trust (103930/Z/14/Z)
Wellcome Trust (75880)