title: Questionable expression of unstable DQ heterodimer containing HLA-DQA1*01:07.
abstract: Human leukocyte antigens (HLA)-DQA1*01:07 was identified as an HLA-DQ blank specificity that segregated with the serological HLA-A2, -B7, -DR14, -DR52 haplotype, which carried DQB1*05:03. The blank specificity of DQA1*01:07-DQB1*05:03 may be because of lack of reactivity of available typing sera, or disruption of proper assembly of DQ heterodimer. The cDNA sequence of DQA1*01:07 is nearly identical to DQA1*01:04 except for a variant at position 304, which results in the replacement of an arginine with a cysteine at 79α. To determine whether the DQA1*01:07 product can be expressed on cell-surface, we co-expressed DQA1*01:07 with various DQB1*05 or *06 alleles in fibroblast cells. Cell-surface expression of DQ was detectable when DQA1*01:07 was co-expressed with DQB1*06:04 but undetectable with other DQB1*05 and DQB1*06 alleles, including DQB1*05:03, to which DQA1*01:07 was encoded in cis. These data suggest that DQA1*01:07 may act as a phenotypically null allele in the DQA1*01:07-DQB1*05:03 haplotype, while it can be expressed at a low level in the presences of certain DQB1*06 alleles, such as DQB1*06:04, in trans. Based on the null or low expression of DQA1*01:07 as shown in the previous and present studies, DQA1*01:07 has recently been renamed to DQA1*01:07Q, indicating its questionable expression.
authors.affiliation: Department of Human Genetics, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan.|Research Center for Hepatitis and Immunology, National Center for Global Health and Medicine, Chiba, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Miyadera
authors.affiliation: Department of Laboratory Medicine, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands.
authors.forename: L B
authors.initials: LB
authors.lastname: Bungener
authors.affiliation: RIKEN Structural Biology Laboratory, Yokohama, Japan.
authors.forename: S
authors.initials: S
authors.lastname: Kusano
authors.affiliation: RIKEN Structural Biology Laboratory, Yokohama, Japan.
authors.forename: S
authors.initials: S
authors.lastname: Yokoyama
authors.affiliation: Department of Human Genetics, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Tokunaga
authors.affiliation: Department of Laboratory Medicine, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands.
authors.forename: B G
authors.initials: BG
authors.lastname: Hepkema
mesh_terms: D000483:Alleles; D019943:Amino Acid Substitution; D000818:Animals; D018076:DNA, Complementary / Q000235:genetics; D019281:Dimerization; D015870:Gene Expression; D059866:HLA-DQ beta-Chains / Q000737:chemistry*; D006239:Haplotypes; D006650:Histocompatibility Testing; D006801:Humans; D051379:Mice; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D041681:NIH 3T3 Cells; D010641:Phenotype; D055550:Protein Stability; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D009626:Terminology as Topic; D014161:Transduction, Genetic
chemical_list: D018076:DNA, Complementary; D059866:HLA-DQ beta-Chains; C069051:HLA-DQB1 antigen
keywords: HLA-DQ; human leukocyte antigens; low expression allele; questionable expression allele