THE REMARKABLE EVOLUTIONARY HISTORY OF THE HUMAN AMYLASE GENES

Analysis of the structures of the human amylase genes has demonstrated that this multigene family contains at least five tandem gene copies, closely related in sequence but with distinct tissue specific express ion. The structures of the genes demonstrate that the human salivary a mylase gene was derived from a preexisting pancreatic amylase gene. In sertion of a retrovirus upstream of the amylase gene is responsible fo r the alteration in tissue specificity. A parotid specific enhancer ha s been identified within the retrovirus by expression studies in trans genic mice. The independent origin of salivary amylase in rodents and primates suggests that there has been strong evolutionary selection fo r amylase in saliva. The amylase genes demonstrate a novel mechanism f or evolution of new patterns of tissue specific gene expression.