Original article

Blood Transfusion - 1 2022 (January-February)

Molecular characterization of rare D--/D-- variants in individuals of Indian origin

Authors

Key words: rare blood group, RHD variants, rearrangement, RHD-RHCE hybrid, D--
Publication Date: 2020-11-27

Abstract

Background - Rh antigens are critical in haemolytic disease of the foetus and newborn (HDFN). The D-- phenotype is a rare blood group characterised by the lack of expression of C, c, E and e antigens at the surface of red blood cells because of mutations in both RHCE alleles inactivating the expression of a "normal" protein. The aim of the study was to determine the molecular basis of D-- individuals of Indian origin.
Materials and methods - Ten Rh D-positive postnatal women who had produced antibodies against all Rh antigens, except D, leading to HDFN and foetal loss, were investigated. Extensive serological and molecular (polymerase chain reaction [PCR] using sequence-specific primers), quantitative multiplex PCR of short fluorescent fragments (QMPSF), and Sanger sequencing analyses were carried out.
Results - Serological testing with anti-C, anti-c, anti-E, and anti-e reagents showed absence of the four antigens in all ten index cases, as well as in three siblings. Flow cytometry indicated absence of these antigens with a typical exalted expression of the D antigen, thus confirming the rare D-- phenotype. Molecular analysis by QMPSF suggested homozygous CE-D hybrid alleles causing the D-- phenotype: RHCE-D(3-9)-CE (n = 11), RHCE-D(3-8)-CE (n=1), and RHCE-D(2-6)-CE (n=1).
Discussion - For the first time, we report the molecular basis of the D-- phenotype in the Indian population. Identification and characterisation of RHCE-null variants by molecular methods can help resolve transfusion-related problems in these individuals. Family studies of index cases helped to identify rare blood donors and offer counselling to females of child-bearing age on the complications involved in such pregnancies.

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Authors

Swati Kulkarni - 1Department of Transfusion Medicine, ICMR-National Institute of Immunohaematology, Mumbai, India

Garima Mishra - 1Department of Transfusion Medicine, ICMR-National Institute of Immunohaematology, Mumbai, India

Harita Maru - Department of Transfusion Medicine, ICMR-National Institute of Immunohaematology, Mumbai, India

Disha Parchure - Department of Transfusion Medicine, ICMR-National Institute of Immunohaematology, Mumbai, India

Debasish Gupta - Department of Transfusion Medicine, Sree Chitra Tirunal Institute for Medical Sciences and Technology, Trivandrum, India

Anantpreet Kaur Bajaj - Department of Immunhaematology and Blood Transfusion, Armed Forces Medical College, Pune, India

Sangeeta Pahuja Sindhwani - Department of Immunhaematology and Blood Transfusion, Lady Hardinge Medical College, New Delhi, India

Anand Chaphekar - KEM Hospital Blood Bank, Pune, India

Ripal Shah - Prathama Blood Centre, Ahmedabad, India

Claude Férec - Génétique, Génomique Fonctionnelle et Biotechnologies", INSERM, EFS, Université de Brest, UMR1078, IBSAM, Brest, France; Service de Génétique Médicale, Centre Hospitalier Régional et Universitaire (CHRU) de Brest, Hôpital Morvan, Brest, France

Manisha Madkaikar - Department of Transfusion Medicine, ICMR-National Institute of Immunohaematology, Mumbai, India

Yann Fichou - Génétique, Génomique Fonctionnelle et Biotechnologies", INSERM, EFS, Université de Brest, UMR1078, IBSAM, Brest, France; Laboratory of Excellence (LabEx) GR-Ex, Paris, France

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