DMP4 (FAM20C), from a rat odontoblast cDNA library. Using a partial rat DMP4 sequence, they obtained a full-length mouse Dmp4 cDNA, which encodes a deduced 579-amino acid protein with a 26-amino acid signal sequence, a Greek key calcium-binding domain, and a conserved C-terminal domain. The protein contains several potential N-linked glycosylation sites and has a calculated pI of 7.1, much different from other dentin matrix proteins, which are acidic. Northern blot analysis of mouse tissues showed highest levels of transcript in the dental pulp-odontoblast complex, moderate expression in bone, and low expression in kidney, liver, brain, and lung. Transfection experiments demonstrated perinuclear and cytoplasmic staining, consistent with an endoplasmic reticulum localization.