Molecular Evolution of HR, a Gene That Regulates the Postnatal Cycle of the Hair Follicle

The document presents a study on the molecular evolution of the Hairless (HR) gene, which is crucial for the regulation of the postnatal hair follicle cycle. The study found that mutations in the HR gene can cause alopecia universalis congenita (AUC), a condition characterized by complete hair loss. The HR gene was shown to have evolved rapidly in humans, with evidence of positive selection in the human lineage. A total of 114 single nucleotide polymorphisms (SNPs) were identified in humans, and neutrality tests suggested a significant departure from neutrality, indicating positive selection. The HR gene was found to be conserved among mammals but absent in non-mammalian vertebrates, suggesting it may have originated in the mammalian ancestor. The study concluded that the HR gene has undergone positive selection in primates, particularly in humans, which may have contributed to the functional diversification of the HR protein and the evolutionary changes in hair follicle morphogenesis. Seven amino acid sites were identified as likely involved in altering HR protein structure/function during human evolution. The findings highlight the importance of HR in hair evolution and its potential role in human hair disorders.