Cementum is the outer-, mineralized-tissue covering the tooth root and an essential part of the system of periodontal tissue that anchors the tooth to the bone. Periodontal disease results from the destructive behavior of the host elicited by an infectious biofilm adhering to the tooth root and left untreated, may lead to tooth loss. We describe a novel protocol for identifying peptide sequences from native proteins with the potential to repair damaged dental tissues by controlling hydroxyapatite biomineralization. Using amelogenin as a case study and a bioinformatics scoring matrix, we identified regions within amelogenin that are shared with a set of hydroxyapatite-binding peptides (HABPs) previously selected by phage display. One 22-amino acid long peptide regions referred to as amelogenin-derived peptide 5 (ADP5) was shown to facilitate cell-free formation of a cementum-like hydroxyapatite mineral layer on demineralized human root dentin that, in turn, supported attachment of periodontal ligament cells in vitro. Our findings have several implications in peptide-assisted mineral formation that mimic biomineralization. By further elaborating the mechanism for protein control over the biomineral formed, we afford new insights into the evolution of protein-mineral interactions. By exploiting small peptide domains of native proteins, our understanding of structure-function relationships of biomineralizing proteins can be extended and these peptides can be utilized to engineer mineral formation. Finally, the cementomimetic layer formed by ADP5 has the potential clinical application to repair diseased root surfaces so as to promote the regeneration of periodontal tissues and thereby reduce the morbidity associated with tooth loss.
Amelogenin ; chemistry ; physiology ; Biomimetic Materials ; chemistry ; Calcium-Binding Proteins ; Carrier Proteins ; physiology ; Cementogenesis ; physiology ; Dental Cementum ; chemistry ; Humans ; Peptide Fragments ; Peptide Mapping ; methods ; Peptides ; physiology ; Protein Engineering ; methods ; Sequence Homology, Amino Acid ; Tissue Engineering ; methods ; Tooth Calcification ; physiology

In the canonical version of evolution by gene duplication,one copy is kept unaltered while the other is free to evolve.This process of evolutionary experimentation can persist for millions of years.Since it is so short lived in comparison to the lifetime of the core genes that make up the majority of most genomes,a substantial fraction of the genome and the transcriptome may-in principle-be attributable to what we will refer to as "evolutionarytransients",referring here to both the process and the genes that have gone or are undergoing this process.Using the rice gene set as a test case,we argue that this phenomenon goes a long way towards explaining why there are so many more rice genes than Arabidopsis genes,and why most excess rice genes show low similarity to eudicots.