title: RNA processing and protein expression of HLA-B*07:44N.
abstract: The assignment of human leukocyte antigen (HLA) null alleles is clinically relevant in the setting of stem cell transplantation. Cell surface expression profiling and mRNA processing analysis of the HLA-B allele previously designated as B*07:44, have been performed.
  
  
  
  Cell surface expression of HLA-B*07:44 was determined using flow cytometry. Genomic full-length and HLA-B*07-specific cDNA sequencing were carried out by Sanger procedure.
  
  
  
  Flow cytometric analysis confirmed previous serologic results and demonstrated a lack of cell membrane expression of the HLA-B protein. The mRNA processing, studied using direct HLA-B*07-specific cDNA sequencing, revealed the presence of a unique, aberrantly spliced mRNA, with a deletion of the last 43 bp on the 5'-end of exon 4. The substitution from T to G at genomic position 1799 compared to B*07:02:01 introduced a new and stronger splice donor site at exon 4. This alternative splicing produced an mRNA containing a premature stop codon at position 280, explaining the absence of mature HLA-B7 protein on the cell surface.
  
  
  
  These findings led us to consider this HLA-B variant as a HLA null allele. The World Health Organization (WHO) Nomenclature Committee has since renamed this variant B*07:44N .
authors.affiliation: Departamento de Histocompatibilidad, Centro de Transfusión de la Comunidad de Madrid, Madrid, Spain.
authors.forename: A
authors.identifier: 0000-0001-7137-3304
authors.initials: A
authors.lastname: Balas
authors.affiliation: Departamento de Histocompatibilidad, Centro de Transfusión de la Comunidad de Madrid, Madrid, Spain.
authors.forename: F
authors.initials: F
authors.lastname: García-Sánchez
authors.affiliation: Departamento de Histocompatibilidad, Centro de Transfusión de la Comunidad de Madrid, Madrid, Spain.
authors.forename: J L
authors.initials: JL
authors.lastname: Vicario
mesh_terms: D000483:Alleles; D017398:Alternative Splicing; D001483:Base Sequence; D016026:Bone Marrow Transplantation; D003001:Cloning, Molecular; D018388:Codon, Terminator; D018076:DNA, Complementary / Q000235:genetics / Q000276:immunology; D005091:Exons; D005434:Flow Cytometry; D015793:HLA-B7 Antigen / Q000235:genetics* / Q000276:immunology; D006801:Humans; D012333:RNA, Messenger / Q000235:genetics* / Q000276:immunology; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D017384:Sequence Deletion; D009626:Terminology as Topic; D014019:Tissue Donors
chemical_list: D018388:Codon, Terminator; D018076:DNA, Complementary; C425023:HLA-B*07 antigen; D015793:HLA-B7 Antigen; D012333:RNA, Messenger
keywords: B*07:44N; HLA; null allele; splicing