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Molecular background of VS and weak C expression in blacks
B H Faas1, E A Beckers, P Wildoer
1Central Laboratory of the Netherlands Red Cross Blood Transfusion Service, University of Amsterdam, The Netherlands.
Transfusion
|January 1, 1997
Summary
The Rh system
Area of Science:
- Genetics
- Immunology
- Molecular Biology
Background:
- The Rh blood group system is complex, featuring numerous antigens.
- The VS antigen (Rh20) is common in Black populations but rare in Whites.
- VS positivity often correlates with weakened expression of Rh antigens e and C.
Purpose of the Study:
- To investigate the genetic basis of the VS antigen in the Rh system.
- To understand the molecular mechanisms behind the associated weak expression of C and e antigens.
Main Methods:
- Analysis of RHCE gene DNA and transcripts from VS-positive Black donors.
- Sequencing of transcripts from donors with weak C expression.
- Genomic DNA analysis for other VS-positive donors.
Main Results:
- A single-point mutation (C733G) in RHCE exon 5, causing Leu245Val substitution, is linked to VS antigen.
- This mutation may also explain weak e expression due to its location in the same exon.
- Hybrid D-CE-D transcripts were identified in donors with weak C expression, lacking C-associated markers.
Conclusions:
- A hybrid RHCE gene, containing a Leu62Phe substitution and the Leu245Val substitution (for VS), is likely responsible for weak C expression.
- This hybrid gene likely cosegregates with a C allele encoding Cys16 and Val245.
- This genetic mechanism explains the frequent co-occurrence of weak C expression and VS positivity in Black individuals.