Molecular analysis of the GYPB gene to infer S, s, and U phenotypes in an admixed population of Minas Gerais, Brazil

OBJECTIVE: To implement genotyping for S, s and U antigens of the MNS blood group system at the Fundação Hemominas and to evaluate the occurrence of GYPB gene polymorphisms associated with the U- and U+var phenotypes and deletion of the GYPB gene for the first time in an admixed population of Minas Gerais, Brazil. The S, s and U antigens can cause transfusion reactions and perinatal hemolytic disease. Genotyping is a useful tool in immunohematology, especially when phenotyping cannot be performed. METHODS: Ninety-six samples from blood donors and patients with sickle cell disease previously phenotyped for the S, s and U antigens were selected. Allele-specific primer polymerase chain reaction (ASP-PCR) and polymerase chain reaction -restriction fragment length polymorphism (PCR-RFLP) assays were employed to identify the GYPB*S and GYPB*s alleles and the GYPB(P2) and GYPB(NY) variants, as well as deletion of the GYPB gene. RESULTS: The results of allele-specific genotyping (GYPB*S and GYPB*s) were totally in agreement with the phenotyping of S+ (n = 56), s+ (n = 60) and s- (n = 35) samples. However, the GYPB*S allele, in association with the GYPB(P2) variant, was detected in 17.5% of the S- samples (n = 40), which shows the importance of assessing this variant in the Brazilian population. Of the S-s- samples (n = 10), 60% had the deletion of the GYPB gene and 40% were homozygous or hemizygous for the GYPB(P2) variant. CONCLUSION: Genotyping was an effective strategy to infer the S, s, and U phenotypes in the admixed population from Minas Gerais (Brazil) and may contribute to transfusion safety.

Genotipagem RhD fetal não invasiva no acompanhamento de gestantes RhD negativo / Non invasive Fetal RHD Genotyping in management of pregnant RhD negative women

O acompanhamento de gestantes de fenótipo RhD negativo é baseado na premissa de que seus fetos podem estar em risco de desenvolver a doença hemolítica perinatal (DHPN) ou eritroblastose fetal, trazendo sérios riscos ao feto em decorrência de hemólise, com consequente anemia, hidropsia e, por vezes, óbito intrauterino. Procedimentos invasivos como amniocentese ou cordocentese podem ser utilizados para se inferir o fenótipo RhD fetal, entretanto, oferecem riscos ao feto e à gestante. Nos últimos anos, o conhecimento sobre a genética dos grupos sanguíneos e o desenvolvimento de técnicas de biologia molecular tem permitido a inferência de fenótipos de grupos sanguíneos a partir da detecção do material genômico. Inicialmente, a genotipagem do DNA fetal para o gene RhD era feita a partir de amostras de amniócitos ou de vilosidades coriônicas. No entanto, por tratar-se de testes invasivos, traziam risco ao feto e à gestante. A possibilidade de se obter DNA fetal a partir do plasma materno foi um grande avanço na prática clínica, por ser um procedimento não invasivo e, portanto, isento de risco. Esta revisão apresenta os princípios da técnica e os resultados de diferentes protocolos para genotipagem RhD fetal (publicados ao longo dos anos) e qual o seu propósito no acompanhamento das gestantes RhD negativo

The RhD negative pregnant women management has been based on the fact that their fetuses may be at risk of developing hemolytic diseases (DHPN) or erythroblastosis fetalis. This condition may bring serious risks to the fetus due to hemolysis, with consequent anemia and hydrops and sometimes, intrauterine death. Invasive procedures such as amniocentesis or cordocentesis may be performed to assess the fetal RhD phenotype, however, it offers risks to both fetus and pregnant woman. In recent years, the knowledge about the genetics of blood groups and the development of molecular biology techniques has allowed the inference of blood group phenotypes by the detection of genomic material. Initially, the fetal DNA genotyping for the RHD gene was performed from amniocytes or chorionic villi samples. Unfortunately, these invasive tests could bring risk to the fetus and the pregnant woman. However, the possibility of obtaining fetal DNA from maternal plasma has been a major advance in clinical practice, as being a non-invasive procedure and therefore not providing any risks. This review presents the principles of techniques and results of different protocols for fetal RHD genotyping (published over the years) and its goal on the management of RhD negative pregnant women