In addition to nine functional genes, the human type I hair keratin gene cluster contains a pseudogene,ϕhHaA (KRTHAP1), which is thought to have been inactivated by a single base-pair substitution that introduced a premature TGA termination codon into exon 4. Large-scale genotyping of human, chimpanzee, and gorilla DNAs revealed the homozygous presence of theϕhHaA nonsense mutation in humans of different ethnic backgrounds, but its absence in the functional orthologous chimpanzee (cHaA) and gorilla (gHaA) genes. Expression analyses of the encoded cHaA and gHaA hair keratins served to highlight dramatic differences between the hair keratin phenotypes of contemporary humans and the great apes. The relative numbers of synonymous and non-synonymous substitutions in theϕhHaA and cHaA genes, as inferred by using the gHaA gene as an outgroup, suggest that the human hHaA gene was inactivated only recently, viz., less than 240,000 years ago. This implies that the hair keratin phenotype of hominids prior to this date, and after the Pan-Homo divergence some 5.5 million years ago, could have been identical to that of the great apes. In addition, the homozygous presence of theϕhHaA exon 4 nonsense mutation in some of the earliest branching lineages among extant human populations lends strong support to the "single African origin" hypothesis of modern humans.

Authors and Affiliations

1. German Cancer Research Center, Research Program B, B0500, Im Neuenheimerfeld 280, 69120 Heidelberg, Germany, , , , ,

   Hermelita Winter

2. German Cancer Research Center, Division of Tumor Cell Regulation, 69120 Heidelberg, Germany, , , , ,

   Luis F. Jave-Suarez, Michael A. Rogers & Jürgen Schweizer

3. German Cancer Research Center, Division of Cell Biology, 69120 Heidelberg, Germany, , , , ,

   Lutz Langbein & Silke Praetzel

4. Institute of Medical Genetics, University of Wales College of Medicine, Cardiff CF14 4XN, UK, , , , ,

   Michael Krawczak & David N. Cooper

5. Biomedical Primate Research Centre, Department of Animal Science, 2280 GH Rijswijk, The Netherlands, , , , ,

   Peter J. Heidt

Electronic Publication

Reprints and permissions