title: A new AQP1 null allele identified in a Gypsy woman who developed an anti-CO3 during her first pregnancy.
abstract: OBJECTIVE
  The Colton blood group antigens are carried by the AQP1 water channel. AQP1(-/-) individuals, also known as Colton-null since they express no Colton antigens, do not suffer any apparent clinical consequence but may develop a clinically significant alloantibody (anti-CO3) induced by transfusion or pregnancy. Identification and transfusion support of Colton-null patients are highly challenging, not only due to the extreme rarity of this phenotype, the lack of appropriate reagents in most laboratories, as well as the possibility of confusing it with the recently described CO:-1,-2,3,-4 phenotype where AQP1 is present. This study investigated a new Colton-null case and evaluated three commercially available anti-AQP1s to identify Colton-null red blood cell samples.
  
  
  METHODS
  The Colton-null phenotype was investigated by standard serological techniques, AQP1 sequencing, immunoblot and flow cytometry analyses.
  
  
  RESULTS
  We identified and characterized the Colton-null phenotype in a Gypsy woman who developed an anti-CO3 during her first pregnancy. After developing a simple and robust method to sequence AQP1, we showed that she was apparently homozygous for a new AQP1 null allele, AQP1 601delG, whose product is not expressed in her red blood cells. We also established the Colton specificity of three commercially available anti-AQP1s in immunoblot and/or flow cytometry analyses.
  
  
  CONCLUSIONS
  This Gypsy woman represents the sixth Colton-null case characterized at the serological, genetic and biochemical levels. The validation here of new reagents and methods should facilitate the identification of Colton-null individuals.
authors.affiliation: National Institute of Blood Transfusion, INTS, Paris, France.
authors.forename: C
authors.initials: C
authors.lastname: Saison
authors.forename: T
authors.initials: T
authors.lastname: Peyrard
authors.forename: C
authors.initials: C
authors.lastname: Landre
authors.forename: B A
authors.initials: BA
authors.lastname: Ballif
authors.forename: K A
authors.initials: KA
authors.lastname: Schlosser
authors.forename: I
authors.initials: I
authors.lastname: Dettori
authors.forename: C
authors.initials: C
authors.lastname: Chicheportiche
authors.forename: P
authors.initials: P
authors.lastname: Nemeth
authors.forename: J-P
authors.initials: JP
authors.lastname: Cartron
authors.forename: L
authors.initials: L
authors.lastname: Arnaud
mesh_terms: D000293:Adolescent; D000483:Alleles; D051398:Aquaporin 1 / Q000097:blood / Q000235:genetics* / Q000276:immunology; D001787:Blood Group Incompatibility / Q000097:blood / Q000235:genetics / Q000276:immunology; D005260:Female; D006801:Humans; D007518:Isoantibodies / Q000097:blood* / Q000276:immunology; D009154:Mutation; D011247:Pregnancy; D011250:Pregnancy Complications, Hematologic / Q000097:blood / Q000235:genetics / Q000276:immunology; D006178:Romani People
chemical_list: C496020:AQP1 protein, human; D007518:Isoantibodies; D051398:Aquaporin 1