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


Reviewed October 2008

What is the official name of the SAR1B gene?

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.

What is the normal function of the SAR1B gene?

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.

How are changes in the SAR1B gene related to health conditions?

chylomicron retention disease - caused by mutations in the SAR1B gene

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.

Where is the SAR1B gene located?

Cytogenetic Location: 5q31.1

Molecular Location on chromosome 5: base pairs 134,601,149 to 134,632,843

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

The SAR1B gene is located on the long (q) arm of chromosome 5 at position 31.1.

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 134,601,149 to base pair 134,632,843 on chromosome 5.

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

Where can I find additional information about SAR1B?

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.

What other names do people use for the SAR1B gene or gene products?

  • GTP-binding protein Sara
  • SAR1a gene homolog 2
  • SAR1 gene homolog B (S. cerevisiae)
  • SAR1 homolog B (S. cerevisiae)
  • SARA2
  • secretion associated, Ras related GTPase 1B

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

What glossary definitions help with understanding SAR1B?

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.


  • Charcosset M, Sassolas A, Peretti N, Roy CC, Deslandres C, Sinnett D, Levy E, Lachaux A. Anderson or chylomicron retention disease: molecular impact of five mutations in the SAR1B gene on the structure and the functionality of Sar1b protein. Mol Genet Metab. 2008 Jan;93(1):74-84. Epub 2007 Oct 22. (
  • Hussain MM, Fatma S, Pan X, Iqbal J. Intestinal lipoprotein assembly. Curr Opin Lipidol. 2005 Jun;16(3):281-5. Review. (
  • NCBI Gene (
  • Shoulders CC, Naoumova RP. The genes and proteins of atherogenic lipoprotein production. Biochem Soc Trans. 2004 Feb;32(Pt 1):70-4. Review. (
  • Shoulders CC, Stephens DJ, Jones B. The intracellular transport of chylomicrons requires the small GTPase, Sar1b. Curr Opin Lipidol. 2004 Apr;15(2):191-7. Review. (
  • Silvain M, Bligny D, Aparicio T, Laforêt P, Grodet A, Peretti N, Ménard D, Djouadi F, Jardel C, Bégué JM, Walker F, Schmitz J, Lachaux A, Aggerbeck LP, Samson-Bouma ME. Anderson's disease (chylomicron retention disease): a new mutation in the SARA2 gene associated with muscular and cardiac abnormalities. Clin Genet. 2008 Dec;74(6):546-52. doi: 10.1111/j.1399-0004.2008.01069.x. Epub 2008 Sep 11. (


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: October 2008
Published: February 8, 2016