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

PAX gene family

Reviewed July 2008

What are the PAX genes?

The PAX gene family plays a critical role in the formation of tissues and organs during embryonic development. The PAX gene family is also important for maintaining the normal function of certain cells after birth. To carry out these roles, the PAX genes provide instructions for making proteins that attach to specific areas of DNA and help control the activity (expression) of particular genes. On the basis of this action, PAX proteins are called transcription factors.

After birth, the PAX genes are usually turned off (inactivated), but in some tissues the PAX genes are active. These active genes aid in tissue re-growth and protect against cell death caused by cellular stress (such as increased sodium levels in the cell).

There are nine genes in the PAX gene family. These genes are divided into subgroups based on various aspects of similarity. Subgroup I includes PAX1 and PAX9; subgroup II includes PAX2, PAX5, and PAX8; subgroup III includes PAX3 and PAX7; and subgroup IV includes PAX4 and PAX6.

Mutations in PAX genes lead to disorders that involve the incomplete development of tissues in which a particular PAX gene is expressed. Additionally, the overexpression of PAX genes has been noted in a variety of cancers. It is thought that the cell protection function of PAX genes prevents cell death and permits tumor growth (proliferation).

Which genes are included in the PAX gene family?

The HUGO Gene Nomenclature Committee (HGNC) provides an index of gene families ( and their member genes.

Genetics Home Reference summarizes the normal function and health implications of these members of the PAX gene family: PAX2, PAX3, PAX6, and PAX8.

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

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

  • aniridia
  • coloboma
  • congenital hypothyroidism
  • craniofacial-deafness-hand syndrome
  • Gillespie syndrome
  • microphthalmia
  • Peters anomaly
  • renal coloboma syndrome
  • Waardenburg syndrome
  • WAGR syndrome

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

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

  • University of South Wales Department of Embryology (

What glossary definitions help with understanding the PAX gene family?

cell ; DNA ; embryonic ; expressed ; gene ; proliferation ; sodium ; stress ; tissue ; transcription ; tumor

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 PAX gene family.

  • Robson EJ, He SJ, Eccles MR. A PANorama of PAX genes in cancer and development. Nat Rev Cancer. 2006 Jan;6(1):52-62. Review. (
  • Muratovska A, Zhou C, He S, Goodyer P, Eccles MR. Paired-Box genes are frequently expressed in cancer and often required for cancer cell survival. Oncogene. 2003 Sep 11;22(39):7989-97. (
  • Chi N, Epstein JA. Getting your Pax straight: Pax proteins in development and disease. Trends Genet. 2002 Jan;18(1):41-7. 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: July 2008
Published: February 1, 2016