Dombrock genotyping in a native Congolese cohort reveals two novel alleles.
BACKGROUND
Since variant alleles in the Dombrock (DO) blood group system are common in Africans, DNA typing of DO alleles in an uninvestigated Congolese Teke ethnic group was performed.


METHODS
DO exons were polymerase chain reaction amplified, using genomic DNA extracted from blood samples, and sequenced. Membrane expression in K562 cells transduced with DO-cDNAs using lentiviral vectors was studied by flow cytometry. Amino acid changes were mapped on the protein structure, predicted by homology modeling.


RESULTS
In 41 samples investigated, there were 56 DOB or DOB-WL (68%), 15 DOA (18%), 6 HY (7%), and 3 JO (4%) alleles. The remaining two alleles were novel, that is, DOB-SH-Gln149Lys carrying a 445C>A transversion and DOB-(WL)-Ile175Asn showing a 524T>A transversion on a DOB or DOB-WL background. Transduced K562 cells revealed that DOB-SHGln149Lys variant was expressed to the same extent as DOB-SH but to a lesser extent than the DOB control. The DOB-Ile175Asn variant shows equivalent expression to DOB but is not recognized by monoclonal antibodies MIMA-53. As deduced from the protein model, these missense changes would lead to structure similar to the wild-type one, with only modified surface features.


CONCLUSIONS
Molecular screening of Teke individuals revealed a high frequency of HY and JO alleles and two novel alleles, one on the DOB (or DOB-WL) and one on the DOB-SH background. Expression studies highlighted the impact of changes on Do protein expression. These findings suggest that allelic diversity is greater than expected and that expression level of DO alleles should be taken into account in transfusion
Laboratoire d’Hématologie Moléculaire, EFS Alpes Méditerranée, UMR 6578, Université de la Méditerranée, 207 Boulevard Sainte Marguerite, 13009, Marseille, France.
Sylvie
S
Chapel-Fernandes
Isabelle
I
Callebaut
Gregory R
GR
Halverson
Marion E
ME
Reid
Pascal
P
Bailly
Jacques
J
Chiaroni
D036002:ADP Ribose Transferases / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics; D000483:Alleles; D019943:Amino Acid Substitution; D015331:Cohort Studies; D003223:Congo; D005091:Exons; D005260:Female; D005786:Gene Expression Regulation / Q000235:genetics*; D006801:Humans; D020014:K562 Cells; D008297:Male; D008565:Membrane Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics; D008958:Models, Molecular; D020125:Mutation, Missense; D016133:Polymerase Chain Reaction; D017434:Protein Structure, Tertiary
D008565:Membrane Proteins; D036002:ADP Ribose Transferases; C105234:ART4 protein, human