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Genetics Home Reference: your guide to understanding genetic conditions     A service of the U.S. National Library of Medicine®

PG gene family

Reviewed January 2010

What are the PG genes?

The PG genes provide instructions for making proteins called proteoglycans. A proteoglycan is a molecule that is made up of a core protein attached to one or more sugar molecules called glycosaminoglycan (GAG) chains. Some functions of proteoglycans are determined by their GAG chains.

Proteoglycans can be divided into two classes based on their cellular location: cell surface proteoglycans and extracellular matrix proteoglycans. Cell surface proteoglycans are anchored to the cell membrane, where they interact with other proteins such as growth factors and signaling proteins that are important for cell growth and maintenance. Extracellular matrix proteoglycans are found in the extracellular matrix, which is the intricate lattice of proteins and other molecules that forms in the spaces between cells. These proteoglycans interact with other proteins to facilitate the assembly of the extracellular matrix and ensure its stability. The two classes of proteoglycans are further subdivided into groups based on their core proteins.

Changes in proteoglycan structure and function are associated with several disorders. The signs and symptoms of these disorders vary depending on the proteoglycan gene that is altered. For example, mutations in the DCN gene cause congenital stromal corneal dystrophy, a condition that results in visual impairment, while mutations in the COL9A2 gene cause a disorder of bone development called multiple epiphyseal dysplasia.

Which genes are included in the PG gene family?

The HUGO Gene Nomenclature Committee (HGNC) provides a list of genes in the PG family (

Genetics Home Reference summarizes the normal function and health implications of these members of the PG gene family: ACAN, COL9A1, COL9A2, COL9A3, DCN, GPC3, SMC3, and VCAN.

What conditions are related to genes in the PG gene family?

Genetics Home Reference includes these conditions related to genes in the PG gene family:

  • congenital stromal corneal dystrophy
  • Cornelia de Lange syndrome
  • familial osteochondritis dissecans
  • multiple epiphyseal dysplasia
  • Simpson-Golabi-Behmel syndrome
  • Stickler syndrome
  • Wagner syndrome

Where can I find additional information about the PG gene family?

You may find the following resources about the PG gene family helpful.

  • Essentials of Glycobiology (second edition, 2009): Proteoglycans and Sulfated Glycosaminoglycans (
  • Madame Curie Bioscience Database: Proteoglycans (
  • Molecular Biology of the Cell (fourth edition, 2002): Proteoglycans Are Composed of GAG Chains Covalently Linked to a Core Protein (
  • Molecular Biology of the Cell (fourth edition, 2002): The linkage between a GAG chain and its core protein in a proteoglycan molecule (image) (

What glossary definitions help with understanding the PG gene family?

cell ; cell membrane ; collagen ; congenital ; dysplasia ; extracellular ; extracellular matrix ; gene ; heparan sulfate ; leucine ; molecule ; protein ; proteoglycan ; sulfate

You may find definitions for these and many other terms in the Genetics Home Reference Glossary (


These sources were used to develop the Genetics Home Reference summary for the PG gene family.

  • Schaefer L, Iozzo RV. Biological functions of the small leucine-rich proteoglycans: from genetics to signal transduction. J Biol Chem. 2008 Aug 1;283(31):21305-9. doi: 10.1074/jbc.R800020200. Epub 2008 May 6. Review. (
  • Kirn-Safran C, Farach-Carson MC, Carson DD. Multifunctionality of extracellular and cell surface heparan sulfate proteoglycans. Cell Mol Life Sci. 2009 Nov;66(21):3421-34. doi: 10.1007/s00018-009-0096-1. Epub 2009 Jul 24. Review. (
  • Schaefer L, Schaefer RM. Proteoglycans: from structural compounds to signaling molecules. Cell Tissue Res. 2010 Jan;339(1):237-46. doi: 10.1007/s00441-009-0821-y. Epub 2009 Jun 10. Review. (
  • Schwartz NB, Domowicz M. Proteoglycans in brain development. Glycoconj J. 2004;21(6):329-41. Review. (


The resources on this site should not be used as a substitute for professional medical care or advice. Users seeking information about a personal genetic disease, syndrome, or condition should consult with a qualified healthcare professional. See How can I find a genetics professional in my area? ( in the Handbook.

Reviewed: January 2010
Published: April 17, 2014