DHCR7 gene
Normal Function
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 figure and obtained from foods that come from animals (particularly egg yolks, meat, poultry, fish, and dairy products). It has significant 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 significant for the production of acids used in digestion (bile acids).
Related Information
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Health Conditions Related to Genetic Switches
Smith-Lemli-Opitz syndrome
More than one hundred twenty 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 switch interferes with the normal processing of 7-dehydrocholesterol reductase. Another common mutation occurs frequently in affected individuals of Mediterranean heritage. This mutation substitutes one protein building block (amino acid), called threonine, with another amino acid, methionine, at position ninety three in the enzyme (written as Thr93Met or T93M).
Most of the known DHCR7 mutations switch single amino acids in 7-dehydrocholesterol reductase. These mutations reduce the capability 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 brief enzyme; these mutations eliminate the activity of the enzyme. Without functional 7-dehydrocholesterol reductase, cells are incapable 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 bod systems. It is not known, however, how this disturbance in cholesterol production leads to the specific features of Smith-Lemli-Opitz syndrome.
Related Information
- What is a gene mutation and how do mutations occur?
- What kinds of gene mutations are possible?
- More about Mutations and Health
Chromosomal Location
Cytogenetic Location: 11q13.Four, which is the long (q) arm of chromosome eleven at position 13.Four
Molecular Location: base pairs 71,434,411 to 71,448,431 on chromosome eleven (Homo sapiens Annotation Release 108, GRCh38.p7) ( NCBI )