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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.
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).
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.
Cytogenetic Location: 11q13.4
Molecular Location on chromosome 11: base pairs 71,434,410 to 71,448,430
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 71,434,410 to base pair 71,448,430 on chromosome 11.
See How do geneticists indicate the location of a gene? (http://ghr.nlm.nih.gov/handbook/howgeneswork/genelocation) in the Handbook.
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.
See How are genetic conditions and genes named? (http://ghr.nlm.nih.gov/handbook/mutationsanddisorders/naming) in the Handbook.
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 (http://www.ghr.nlm.nih.gov/glossary).
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? (http://ghr.nlm.nih.gov/handbook/consult/findingprofessional) in the Handbook.