Size Polymorphisms in the Human Ultrahigh Sulfur Hair Keratin-Associated Protein 4, KAP4, Gene Family

The study focused on the human ultrahigh sulfur keratin-associated protein 4 (KAP4) genes, which are crucial for hair fiber structure and are located on chromosome 17q12-21. Previously, a gap in the sequence made it difficult to fully characterize these genes, but the gap was bridged by the human bacterial artificial chromosome clone AC100808. The researchers analyzed the nucleotide sequences from AC100808 and used PCR amplification to identify numerous size polymorphisms in the KAP4 genes. These polymorphisms were primarily due to variations in the sequences that encode cysteine-rich repeat segments. The findings suggest that these polymorphic alleles of the KAP4 genes may have developed through the deletion and/or duplication of sequences encoding the repeat structures during the course of evolution.