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The official name of this gene is “secretion associated, Ras related GTPase 1B.”
SAR1B is the gene's official symbol. The SAR1B gene is also known by other names, listed below.
The SAR1B gene provides instructions for making a protein found in enterocytes, which are cells that line the intestine and absorb nutrients. Within enterocytes, the SAR1B protein aids in the transport of molecules called chylomicrons. As food is digested after a meal, chylomicrons are formed to carry fat and cholesterol from the intestine into the bloodstream. Chylomicrons are also necessary for the absorption of certain fat-soluble vitamins, such as vitamin E and vitamin D.
Chylomicrons are made up mostly of various types of fats (lipids); they also contain some proteins, mainly a protein called apolipoprotein B-48 that is produced only in the intestine. Because chylomicrons are made up of lipids and proteins, they are known as lipoproteins. Chylomicrons are released from enterocytes into the bloodstream so the body can use the lipids and fat-soluble vitamins they carry. Sufficient levels of fats, cholesterol, and vitamins are necessary for normal growth and development.
More than 10 mutations in the SAR1B gene have been found to cause chylomicron retention disease. Most of these mutations change one protein building block (amino acid) in the SAR1B protein. Other mutations lead to the production of an abnormally small version of the protein that cannot function properly. Mutations disrupt the SAR1B protein's ability to transport chylomicrons within cells, which prevents chylomicron release into the bloodstream. This retention of chylomicrons prevents dietary fats and fat-soluble vitamins from being used by the body, leading to the nutritional and developmental problems seen in people with chylomicron retention disease.
Cytogenetic Location: 5q31.1
Molecular Location on chromosome 5: base pairs 134,601,148 to 134,632,842
The SAR1B gene is located on the long (q) arm of chromosome 5 at position 31.1.
More precisely, the SAR1B gene is located from base pair 134,601,148 to base pair 134,632,842 on chromosome 5.
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 SAR1B 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.
amino acid ; apolipoprotein ; cholesterol ; chylomicrons ; gene ; GTP ; intestine ; protein ; secretion ; soluble ; vitamins
You may find definitions for these and many other terms in the Genetics Home Reference 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.