cDNA sequencing reveals an unexpected splice variation leading to weak KEL2 expression

Area of Science:

• Genetics
• Immunology
• Molecular Biology

Background:

• Routine KEL1 antigen testing in Swiss blood donors.
• A rare KEL:1,-2 phenotype was observed, genotyped as KEL*01.01/KEL*02.

Purpose of the Study:

• Investigate a discrepancy between KEL phenotype and genotype.
• Characterize a novel KEL*02 allele variant.

Main Methods:

• Serological testing (column agglutination, adsorption-elution).
• Molecular analysis including SSP-PCR, exon sequencing, and RNA analysis.
• Bioinformatic tools (SpliceAI, PolyPhen-2) for variant impact assessment.

Main Results:

• Identified a heterozygous missense mutation c.139C>T (p.Arg47Trp) in KEL*02.
• Mutation led to aberrant splicing, causing a frameshift and truncated KEL transcript.
• Very weak KEL2 expression was detected, inconsistent with standard typing.

Conclusions:

• A novel KEL*02 allele variant resulting from c.139C>T mutation was identified.
• The mutation causes variant splicing and produces a truncated, weakly expressed KEL protein.
• This highlights the importance of molecular methods for rare blood group phenotypes.