Tissue distribution and activity testing suggest a similar but not identical function of fetuin-B and fetuin-A

Biochem J. 2003 Nov 15;376(Pt 1):135-45. doi: 10.1042/BJ20030676.


Fetuins are serum proteins with diverse functions including the regulation of osteogenesis and inhibition of unwanted mineralization. Besides the alpha2-Heremans and Schmid glycoprotein/fetuin-A, the recently identified fetuin-B is a second member of the fetuin family [Olivier, Soury, Risler, Smih, Schneider, Lochner, Jouzeau, Fey and Salier (1999) Genomics 57, 352-364; Olivier, Soury, Ruminy, Husson, Parmentier, Daveau and Salier (2000) Biochem. J. 350, 589-597], which belongs to the cystatin superfamily. We compared the expressions of fetuin-B and fetuin-A at the RNA level and established that both genes are most highly expressed in liver tissue. Like fetuin-A, fetuin-B mRNA is also highly expressed in tongue and placenta tissues. We demonstrated for the first time that fetuin-B is also expressed at the protein level in sera and several organs of mouse, rat and human. We isolated contiguous genomic clones containing both fetuin-B and fetuin-A genes, indicating that these genes are closely linked at the genome level. The close proximity of both these genes may explain our observation that fetuin-B expression was decreased in fetuin-A-deficient mice. Unlike fetuin-A, the amount of fetuin-B protein in human serum varied with gender and was higher in females than in males. Functional analysis revealed that fetuin-B, similarly to fetuin-A, is an inhibitor of basic calcium phosphate precipitation, albeit less active when compared with fetuin-A. Therefore fetuin-B may have a function that is partly overlapping, if not identical, with the function of fetuin-A.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Blood Proteins / genetics
  • Blood Proteins / metabolism*
  • Blood Proteins / physiology*
  • Calcium Phosphates / chemistry
  • Chemical Precipitation
  • DNA, Complementary
  • Female
  • Fetuin-B
  • Gene Components
  • Humans
  • Liver / metabolism
  • Male
  • Mice
  • Mice, Inbred C57BL
  • Mice, Inbred DBA
  • Mice, Knockout
  • RNA, Messenger / metabolism
  • Rats
  • Sex Factors
  • Tissue Distribution
  • alpha-2-HS-Glycoprotein
  • alpha-Fetoproteins / genetics
  • alpha-Fetoproteins / metabolism*
  • alpha-Fetoproteins / physiology*


  • AHSG protein, human
  • Ahsg protein, mouse
  • Blood Proteins
  • Calcium Phosphates
  • DNA, Complementary
  • FETUB protein, human
  • Fetub protein, mouse
  • Fetub protein, rat
  • Fetuin-B
  • RNA, Messenger
  • alpha-2-HS-Glycoprotein
  • alpha-Fetoproteins
  • alpha-tricalcium phosphate
  • tetracalcium phosphate
  • calcium phosphate, monobasic, anhydrous
  • calcium phosphate
  • calcium phosphate, dibasic, anhydrous