Biomineralization in humans: making the hard choices in life.

The skeleton, teeth, and otoconia are normally the only mineralized tissues or organs in the human body. We describe physiological biomineralization in collagenous matrices as well as a more derived noncollagenous matrix. The origin of the collagenous matrices used in mineralized skeletal tissues can be traced to a soft tissue in early Metazoa. In early vertebrates, a genetic system coding for ancient soft collagenous tissue was co-opted for biomineralization using redundant genes resulting from whole genome duplication. However, genes more specific to mineralized tissues arose subsequent to the genome duplication by genomically local tandem duplication. These new genes are the basis for a novel genetic system for various mineralized tissues in skeleton and teeth. In addition, any tissue can be abnormally mineralized, and many pathologies of mineralization in humans are known.