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


Reviewed November 2011

What is the official name of the EBP gene?

The official name of this gene is “emopamil binding protein (sterol isomerase).”

EBP is the gene's official symbol. The EBP gene is also known by other names, listed below.

What is the normal function of the EBP gene?

The EBP gene provides instructions for making an enzyme called 3β-hydroxysteroid-Δ8,Δ7-isomerase. This enzyme is responsible for one of the final steps in the production of cholesterol. Specifically, it converts a molecule called 8(9)-cholestenol to lathosterol. Other enzymes then modify lathosterol to produce cholesterol.

Cholesterol is a waxy, fat-like substance that is produced in the body and obtained from foods that come from animals (particularly egg yolks, meat, poultry, fish, and dairy products). Although too much cholesterol is a risk factor for heart disease, this molecule is necessary for normal embryonic development and has important functions both before and after birth. It is a structural component of cell membranes and plays a role in the production of certain hormones and acids used in digestion (bile acids).

How are changes in the EBP gene related to health conditions?

X-linked chondrodysplasia punctata 2 - caused by mutations in the EBP gene

More than 55 mutations in the EBP gene have been found to cause X-linked chondrodysplasia punctata 2, a condition that occurs almost exclusively in females and is characterized by bone, skin, and eye abnormalities. Some of the mutations responsible for this condition in females insert or delete a small amount of genetic material from the EBP gene, while others change single protein building blocks (amino acids) in the 3β-hydroxysteroid-Δ8,Δ7-isomerase enzyme. All of these mutations impair the normal function of the enzyme, preventing cells from producing enough cholesterol. A shortage of this enzyme also allows potentially toxic byproducts of cholesterol production to build up in the body. The combination of low cholesterol levels and an accumulation of other substances likely disrupts the growth and development of many body systems. It is not known, however, how this disturbance in cholesterol production leads to the specific features of X-linked chondrodysplasia punctata 2.

Rarely, a severe form of X-linked chondrodysplasia punctata 2 has been reported in males. These cases result from changes involving single amino acids in the 3β-hydroxysteroid-Δ8,Δ7-isomerase enzyme. Affected males have some of the same features as affected females, as well as changes in the structure of the brain, moderately to profoundly delayed development, and other birth defects.

Where is the EBP gene located?

Cytogenetic Location: Xp11.23-p11.22

Molecular Location on the X chromosome: base pairs 48,521,776 to 48,528,716

(Homo sapiens Annotation Release 107, GRCh38.p2) (NCBI (

The EBP gene is located on the short (p) arm of the X chromosome between positions 11.23 and 11.22.

The EBP gene is located on the short (p) arm of the X chromosome between positions 11.23 and 11.22.

More precisely, the EBP gene is located from base pair 48,521,776 to base pair 48,528,716 on the X chromosome.

See How do geneticists indicate the location of a gene? ( in the Handbook.

Where can I find additional information about EBP?

You and your healthcare professional may find the following resources about EBP helpful.

You may also be interested in these resources, which are designed for genetics professionals and researchers.

What other names do people use for the EBP gene or gene products?

  • 3-beta-hydroxysteroid-Delta(8),Delta(7)-isomerase
  • 3-beta-hydroxysteroid-delta-8,delta-7-isomerase
  • CDPX2
  • CPXD
  • D8-D7 sterol isomerase
  • delta(8)-Delta(7) sterol isomerase
  • emopamil-binding protein (sterol isomerase)
  • sterol 8-isomerase

See How are genetic conditions and genes named? ( in the Handbook.

What glossary definitions help with understanding EBP?

acids ; bile ; cell ; cholesterol ; digestion ; egg ; embryonic ; enzyme ; gene ; molecule ; protein ; toxic

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


  • Ausavarat S, Tanpaiboon P, Tongkobpetch S, Suphapeetiporn K, Shotelersuk V. Two novel EBP mutations in Conradi-Hünermann-Happle syndrome. Eur J Dermatol. 2008 Jul-Aug;18(4):391-3. doi: 10.1684/ejd.2008.0433. Epub 2008 Jun 23. (
  • Braverman N, Lin P, Moebius FF, Obie C, Moser A, Glossmann H, Wilcox WR, Rimoin DL, Smith M, Kratz L, Kelley RI, Valle D. Mutations in the gene encoding 3 beta-hydroxysteroid-delta 8, delta 7-isomerase cause X-linked dominant Conradi-Hünermann syndrome. Nat Genet. 1999 Jul;22(3):291-4. (
  • Furtado LV, Bayrak-Toydemir P, Hulinsky B, Damjanovich K, Carey JC, Rope AF. A novel X-linked multiple congenital anomaly syndrome associated with an EBP mutation. Am J Med Genet A. 2010 Nov;152A(11):2838-44. doi: 10.1002/ajmg.a.33674. (
  • Herman GE, Kelley RI, Pureza V, Smith D, Kopacz K, Pitt J, Sutphen R, Sheffield LJ, Metzenberg AB. Characterization of mutations in 22 females with X-linked dominant chondrodysplasia punctata (Happle syndrome). Genet Med. 2002 Nov-Dec;4(6):434-8. (
  • Ikegawa S, Ohashi H, Ogata T, Honda A, Tsukahara M, Kubo T, Kimizuka M, Shimode M, Hasegawa T, Nishimura G, Nakamura Y. Novel and recurrent EBP mutations in X-linked dominant chondrodysplasia punctata. Am J Med Genet. 2000 Oct 2;94(4):300-5. Review. (
  • Milunsky JM, Maher TA, Metzenberg AB. Molecular, biochemical, and phenotypic analysis of a hemizygous male with a severe atypical phenotype for X-linked dominant Conradi-Hunermann-Happle syndrome and a mutation in EBP. Am J Med Genet A. 2003 Jan 30;116A(3):249-54. (
  • NCBI Gene (
  • Steijlen PM, van Geel M, Vreeburg M, Marcus-Soekarman D, Spaapen LJ, Castelijns FC, Willemsen M, van Steensel MA. Novel EBP gene mutations in Conradi-Hünermann-Happle syndrome. Br J Dermatol. 2007 Dec;157(6):1225-9. Epub 2007 Oct 18. (


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: November 2011
Published: February 8, 2016