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


Reviewed July 2007

What is the official name of the DHCR7 gene?

The official name of this gene is “7-dehydrocholesterol reductase.”

DHCR7 is the gene's official symbol. The DHCR7 gene is also known by other names, listed below.

What is the normal function of the DHCR7 gene?

The DHCR7 gene provides instructions for making an enzyme called 7-dehydrocholesterol reductase. This enzyme is responsible for the final step in cholesterol production in many types of cells. Specifically, 7-dehydrocholesterol reductase converts a molecule called 7-dehydrocholesterol to 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). It has important functions both before and after birth. Cholesterol plays a critical role in embryonic development by interacting with signaling proteins that control early development of the brain, limbs, genital tract, and other structures. It is also a structural component of cell membranes and myelin, the fatty covering that insulates nerve cells. Additionally, cholesterol is used to make certain hormones and is important for the production of acids used in digestion (bile acids).

How are changes in the DHCR7 gene related to health conditions?

Smith-Lemli-Opitz syndrome - caused by mutations in the DHCR7 gene

More than 120 mutations that cause Smith-Lemli-Opitz syndrome have been identified in the DHCR7 gene. The most common mutation, which is written as IVS8-1G>C, alters a single DNA building block (nucleotide) in the gene. This change interferes with the normal processing of 7-dehydrocholesterol reductase. Another common mutation occurs frequently in affected individuals of Mediterranean heritage. This mutation replaces one protein building block (amino acid), called threonine, with another amino acid, methionine, at position 93 in the enzyme (written as Thr93Met or T93M).

Most of the known DHCR7 mutations change single amino acids in 7-dehydrocholesterol reductase. These mutations reduce the ability of this enzyme to convert 7-dehydrocholesterol to cholesterol. Other mutations insert or delete nucleotides in the DHCR7 gene or lead to the production of an abnormally short enzyme; these mutations eliminate the activity of the enzyme. Without functional 7-dehydrocholesterol reductase, cells are unable to produce enough cholesterol. In addition, potentially toxic byproducts of cholesterol production (such as 7-dehydrocholesterol) can build up in the blood and other tissues. The combination of low cholesterol levels and an accumulation of related 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 Smith-Lemli-Opitz syndrome.

Where is the DHCR7 gene located?

Cytogenetic Location: 11q13.4

Molecular Location on chromosome 11: base pairs 71,434,411 to 71,448,431

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

The DHCR7 gene is located on the long (q) arm of chromosome 11 at position 13.4.

The DHCR7 gene is located on the long (q) arm of chromosome 11 at position 13.4.

More precisely, the DHCR7 gene is located from base pair 71,434,411 to base pair 71,448,431 on chromosome 11.

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

Where can I find additional information about DHCR7?

You and your healthcare professional may find the following resources about DHCR7 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 DHCR7 gene or gene products?

  • 7-DHC reductase
  • D7SR
  • delta-7-dehydrocholesterol reductase
  • sterol delta-7-reductase

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

What glossary definitions help with understanding DHCR7?

acids ; amino acid ; bile ; cell ; cholesterol ; digestion ; DNA ; egg ; embryonic ; enzyme ; gene ; methionine ; molecule ; mutation ; nucleotide ; protein ; syndrome ; threonine ; toxic

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


  • Correa-Cerro LS, Porter FD. 3beta-hydroxysterol Delta7-reductase and the Smith-Lemli-Opitz syndrome. Mol Genet Metab. 2005 Feb;84(2):112-26. Epub 2004 Dec 19. Review. (
  • Jira PE, Waterham HR, Wanders RJ, Smeitink JA, Sengers RC, Wevers RA. Smith-Lemli-Opitz syndrome and the DHCR7 gene. Ann Hum Genet. 2003 May;67(Pt 3):269-80. Review. (
  • NCBI Gene (
  • Nowaczyk MJ, Martin-Garcia D, Aquino-Perna A, Rodriguez-Vazquez M, McCaughey D, Eng B, Nakamura LM, Waye JS. Founder effect for the T93M DHCR7 mutation in Smith-Lemli-Opitz syndrome. Am J Med Genet A. 2004 Mar 1;125A(2):173-6. (
  • Nowaczyk MJ, Waye JS. The Smith-Lemli-Opitz syndrome: a novel metabolic way of understanding developmental biology, embryogenesis, and dysmorphology. Clin Genet. 2001 Jun;59(6):375-86. Review. (
  • Porter FD. RSH/Smith-Lemli-Opitz syndrome: a multiple congenital anomaly/mental retardation syndrome due to an inborn error of cholesterol biosynthesis. Mol Genet Metab. 2000 Sep-Oct;71(1-2):163-74. Review. (
  • Tulenko TN, Boeze-Battaglia K, Mason RP, Tint GS, Steiner RD, Connor WE, Labelle EF. A membrane defect in the pathogenesis of the Smith-Lemli-Opitz syndrome. J Lipid Res. 2006 Jan;47(1):134-43. Epub 2005 Oct 28. (
  • Waye JS, Krakowiak PA, Wassif CA, Sterner AL, Eng B, Nakamura LM, Nowaczyk MJ, Porter FD. Identification of nine novel DHCR7 missense mutations in patients with Smith-Lemli-Opitz syndrome (SLOS). Hum Mutat. 2005 Jul;26(1):59. (
  • Yu H, Patel SB. Recent insights into the Smith-Lemli-Opitz syndrome. Clin Genet. 2005 Nov;68(5):383-91. Review. Erratum in: Clin Genet. 2005 Dec;68(6):570. (


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 2007
Published: February 1, 2016