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TITLE: THE PHYLOGENIES OF INTRONS 4–7 DEMONSTRATE AN INCONSISTENT PATTERN BETWEEN HLA–C GROUP TOPOLOGIES

Holger–Andreas Elsner,¹ Rainer Blasczyk.<sup>1

1</sup>Department of Transfusion Medicine, Hannover Medical School, Hannover, Germany

For most HLA–C alleles coding sequences of the 3` part of the gene still need to be determined, and no systematic studies about the 3` non–coding regions exist. In this study we have sequenced introns 4–7 in 31 HLA–C alleles representing all allelic groups except of Cw*13, using a haplotype–specific amplification strategy. Three novel intronic variants were detected: Cw*0401101new differs from the common variant by a transition (A→G) at position 107 in intron 5; Cw*14021new is characterized by a transversion (G→T) at position 11 of intron 5; and Cw*1701new has a transversion (G→T) at position 156 of intron 7. In the phylogenetic analysis HLA–C alleles were mostly characterized by homogeneity within groups. Moreover, Cw*0102, Cw*04 alleles, and Cw*18 alleles shared identical sequences in all 3` introns, which suggests that they might represent a family. This idea is supported by the close relationship of these allelic groups with regard to their complete coding sequences. However, there was no support for the presence of further allelic families e.g. as described for HLA–A and –B. For this reason the phylogeny only allows the confirmation of three rather rough HLA–C lineages (Cw*07, Cw*17, and all other HLA–C alleles). The homogeneity within allelic groups combined with the inconsistent pattern between group topologies may indicate ancient recombinatory activity in the 3` part of HLA–C which later shifted to the 5` part, there resulting in allelic diversity. Apart from further phylogenetic studies about HLA diversity and diversification, the sequence data obtained in this study may prove valuable for the development of a haplotype–specific sequencing strategy for the 3` exons of HLA–C and for the explanation of recombination events in newly described HLA–C alleles.