title: A Heterozygous RAB27A Mutation Associated with Delayed Cytolytic Granule Polarization and Hemophagocytic Lymphohistiocytosis.
abstract: Frequently fatal, primary hemophagocytic lymphohistiocytosis (HLH) occurs in infancy resulting from homozygous mutations in NK and CD8 T cell cytolytic pathway genes. Secondary HLH presents after infancy and may be associated with heterozygous mutations in HLH genes. We report two unrelated teenagers with HLH and an identical heterozygous RAB27A mutation (c.259G→C). We explore the contribution of this Rab27A missense (p.A87P) mutation on NK cell cytolytic function by cloning it into a lentiviral expression vector prior to introduction into the human NK-92 cell line. NK cell degranulation (CD107a expression), target cell conjugation, and K562 target cell lysis was compared between mutant- and wild-type-transduced NK-92 cells. Polarization of granzyme B to the immunologic synapse and interaction of mutant Rab27A (p.A87P) with Munc13-4 were explored by confocal microscopy and proximity ligation assay, respectively. Overexpression of the RAB27A mutation had no effect on cell conjugate formation between the NK and target cells but decreased NK cell cytolytic activity and degranulation. Moreover, the mutant Rab27A protein decreased binding to Munc13-4 and delayed granzyme B polarization toward the immunologic synapse. This heterozygous RAB27A mutation blurs the genetic distinction between primary and secondary HLH by contributing to HLH via a partial dominant-negative effect.
authors.affiliation: Division of Pediatric Rheumatology, University of Alabama at Birmingham, Birmingham, AL 35233;
authors.forename: Mingce
authors.initials: M
authors.lastname: Zhang
authors.affiliation: Divisione di Reumatologia Pediatrica, Ospedale Pediatrico Bambino Gesù, 00165 Rome, Italy;
authors.forename: Claudia
authors.initials: C
authors.lastname: Bracaglia
authors.affiliation: Divisione di Reumatologia Pediatrica, Ospedale Pediatrico Bambino Gesù, 00165 Rome, Italy;
authors.forename: Giusi
authors.initials: G
authors.lastname: Prencipe
authors.affiliation: Division of Pediatric Hematology-Oncology, University of Alabama at Birmingham, Birmingham, AL 35233;
authors.forename: Christina J
authors.initials: CJ
authors.lastname: Bemrich-Stolz
authors.affiliation: Division of Pediatric Rheumatology, University of Alabama at Birmingham, Birmingham, AL 35233; Division of Clinical Immunology and Rheumatology, University of Alabama at Birmingham, Birmingham, AL 35294;
authors.forename: Timothy
authors.initials: T
authors.lastname: Beukelman
authors.affiliation: Division of Pediatric Gastroenterology, University of Alabama at Birmingham, Birmingham, AL 35233;
authors.forename: Reed A
authors.initials: RA
authors.lastname: Dimmitt
authors.affiliation: Division of Clinical Immunology and Rheumatology, University of Alabama at Birmingham, Birmingham, AL 35294;
authors.forename: W Winn
authors.initials: WW
authors.lastname: Chatham
authors.affiliation: Human Genetics, University of Cincinnati, Cincinnati, OH 45229;
authors.forename: Kejian
authors.initials: K
authors.lastname: Zhang
authors.affiliation: Division of Clinical Immunology and Rheumatology, University of Alabama at Birmingham, Birmingham, AL 35294;
authors.forename: Hao
authors.identifier: http://orcid.org/0000-0002-4720-5471
authors.initials: H
authors.lastname: Li
authors.affiliation: Department of Microbiology, University of Alabama at Birmingham, Birmingham, AL 35294; and.
authors.forename: Mark R
authors.initials: MR
authors.lastname: Walter
authors.affiliation: Divisione di Reumatologia Pediatrica, Ospedale Pediatrico Bambino Gesù, 00165 Rome, Italy;
authors.forename: Fabrizio
authors.initials: F
authors.lastname: De Benedetti
authors.affiliation: Division of Pediatric Rheumatology, University of Cincinnati, Cincinnati, OH 45229.
authors.forename: Alexei A
authors.initials: AA
authors.lastname: Grom
authors.affiliation: Division of Pediatric Rheumatology, University of Alabama at Birmingham, Birmingham, AL 35233; Division of Clinical Immunology and Rheumatology, University of Alabama at Birmingham, Birmingham, AL 35294; rcron@peds.uab.edu.
authors.forename: Randy Q
authors.initials: RQ
authors.lastname: Cron
mesh_terms: D000293:Adolescent; D015550:Cell Degranulation / Q000235:genetics* / Q000276:immunology; D002460:Cell Line; D003594:Cytoplasmic Granules / Q000378:metabolism; D005260:Female; D006579:Heterozygote; D006801:Humans; D047468:Immunoprecipitation; D007694:Killer Cells, Natural / Q000276:immunology*; D051359:Lymphohistiocytosis, Hemophagocytic / Q000235:genetics* / Q000276:immunology / Q000378:metabolism; D008297:Male; D018613:Microscopy, Confocal; D020125:Mutation, Missense; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014161:Transduction, Genetic; D020691:rab GTP-Binding Proteins / Q000235:genetics* / Q000276:immunology; D000075745:rab27 GTP-Binding Proteins
chemical_list: D000075745:rab27 GTP-Binding Proteins; C066694:RAB27A protein, human; D020691:rab GTP-Binding Proteins