Six genes expressed in bones and teeth encode the current members of the SIBLING family of proteins

Connect Tissue Res. 2003;44 Suppl 1:33-40.


Bone sialoprotein (BSP), dentin matrix protein 1 (DMP1), dentin sialophosphoprotein (DSPP), enamelin (ENAM), matrix extracellular phosphoglycoprotein (MEPE), and osteopontin (OPN) are glycophosphoproteins expressed in bones and/or teeth. Direct comparison of their amino acid sequences do not suggest that they belong to a single genetic family, but a detailed analysis of their chromosomal location and gene structure does. Analysis of human brain mRNA by RT-PCR has led to the discovery of two additional exons thereby making it more convincing that MEPE is a member of the SIBLING (Small Integrin-Binding LIgand, N-linked Glycoprotein) family. We propose that the members of this SIBLING family are extended, flexible proteins in solution that can facilitate the formation of a number of different complexes. For example, OPN can bridge complement Factor H to either an RGD-dependent integrin or to CD44 forming a membrane-bound complex that actively suppresses the alternate complement pathway. Two possible mechanisms for inhibiting the lytic pathway of alternate complement are presented.

MeSH terms

  • Animals
  • Bone and Bones / chemistry
  • Bone and Bones / metabolism*
  • Chromosomes, Human, Pair 4 / genetics
  • Dental Enamel Proteins / genetics
  • Extracellular Matrix Proteins*
  • Gene Expression Regulation*
  • Glycoproteins / genetics
  • Humans
  • Integrin-Binding Sialoprotein
  • Mice
  • Osteopontin
  • Phosphoproteins / genetics*
  • Protein Precursors
  • Sequence Alignment
  • Sequence Homology, Amino Acid
  • Sialoglycoproteins / genetics*
  • Tooth / chemistry
  • Tooth / metabolism*


  • DMP1 protein, human
  • Dental Enamel Proteins
  • Dmp1 protein, mouse
  • Extracellular Matrix Proteins
  • Glycoproteins
  • IBSP protein, human
  • Ibsp protein, mouse
  • Ibsp protein, rat
  • Integrin-Binding Sialoprotein
  • MEPE protein, human
  • Phosphoproteins
  • Protein Precursors
  • SPP1 protein, human
  • Sialoglycoproteins
  • Spp1 protein, mouse
  • Spp1 protein, rat
  • dentin sialophosphoprotein
  • tuftelin
  • Osteopontin