Polymorphisms in the human high sulfur hair keratin-associated protein 1, KAP1, gene family

Hair fiber differentiation and maturation involves the close interaction between hair keratins and their associated proteins, KAPs. Recently, a cluster of seven human KAP multigen families has been identified on chromosome 17q12-21 among which were four hKAP1 genes (hKAP1.1B, hKAP1.3, hKAP1.4, and hKAP1.5). In addition, there were previous as well as recent reports on four additional hKAP1 genes (hKAP1.1A, hKAP1.2, hKAP1.6, and hKAP1.7) with unknown chromosomal location. In this study, we have analyzed these eight hKAP1 genes in unrelated Japanese and Caucasian individuals and discovered that hKAP1.1A, hKAP1.6, and hKAP1.7 represent size polymorphisms of the hKAP1.1B gene. In addition, we show that hKAP1.2 as well as three hitherto unknown genes (hKAP1.8A, hKAP1.8B, and hKAP1.9) are size polymorphisms of the hKAP1.3 gene. In contrast, no polymorphic alleles were found for the hKAP1.4 and hKAP1.5 genes. We provide evidence that the polymorphic hKAP1.1B and hKAP1.3 alleles arose mainly by intragenic deletion and/or duplication events of distinct pentapeptide repeats typical for hKAP1 genes. We also demonstrate the occurrence of both frequent and rare population-specific hKAP1.1B and hKAP1.3 alleles, which were obviously generated after the divergence of the Caucasian and Japanese lineage. In addition, by means of a pan-hKAP1 antibody, we confirm the previous hKAP1 family mRNA localization data in the middle to upper cortex of the human anagen hair follicle.