POINT MUTATIONS CHARACTERIZE KEL10, THE KEL3, KEL4, AND KEL21 ALLELES, AND THE KEL17 AND KEL11 ALLELES

Background: The Kell blood group system is complex, consisting of five sets of alleles and expressing high- and low-incidence antigens and a t least 11 other independently expressed antigens. The molecular basis of two sets of alleles: KEL1 (K) and KEL2 (k) and KEL6 (Js(a)) and KE L7 (Js(b)) have been elucidated as single-base mutations leading to am ino acid changes. The molecular basis for the KEL3 (Kp(a)), KEL4 (Kp(b )), and KEL21 (Kp(c)) alleles, the KEL11 (Cote) and KEL17( Wk(a)) alle les, and for KEL10 (UIa) is now reported. Study Design and Methods: Ge nomic DNA from unrelated individuals with KEL:3,-4,-21 [Kp(a+b-c-)], K EL:-3,-4,21 [Kp(a-b-c+)], KEL:17,-11, and KEL:10 (UIa) phenotypes was amplified by polymerase chain reaction (PCR) with primers for the 19 e xons of KEL. The PCR products were sequenced and compared to the DNA s equences of a common Kell system phenotype, KEL:-3,4,-21,-17,-10. Base mutations found were confirmed by restriction fragment length polymor phism analysis in which DNA of unrelated persons with similar red cell phenotypes was used. Results: In all cases, single-base mutations wer e responsible for the expression of the various antigens. In KEL3 (Kp( a)), KEL4 (KPb), and KEL21 (Kp(c)), point mutations at the same codon in exon 8, encoding amino acid residue 281, distinguish the three gene s. KEL4 has the CGG codon for arginine, KEL3 has the TGG codon for try ptophan, and KEL21 has the CAG codon for glutamine. KEL 17 has a T1025 C mutation in exon 8, encoding a valine-to-alanine amino acid change a t residue 302. KEL10 has an A1601T mutation in exon 13, encoding a glu tamic acid-to-valine change at residue 494. In all cases, the point mu tations created restriction enzyme sites, and PCR-based restriction fr agment length polymorphisms confirmed that these point mutations occur red in unrelated persons with the same red cell phenotype. Conclusion: Single-base substitutions characterize the KEL3, KEL21, KEL17, and KE L10 genes. The allelic relationship of KEL3, KEL4, and KEL21 was confi rmed because the mutations occur in the same codon, expressing differe nt amino acids, PCR-based restriction fragment length polymorphisms ca n be used to distinguish genotypes.