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


Reviewed August 2011

What is the official name of the RASA1 gene?

The official name of this gene is “RAS p21 protein activator 1.”

RASA1 is the gene's official symbol. The RASA1 gene is also known by other names, listed below.

What is the normal function of the RASA1 gene?

The RASA1 gene provides instructions for making a protein called p120-RasGAP. This protein helps regulate the RAS/MAPK signaling pathway, which transmits signals from outside the cell to the cell's nucleus. The RAS/MAPK signaling pathway helps direct several important cell functions, including the growth and division (proliferation) of cells, the process by which cells mature to carry out specific functions (differentiation), and cell movement. The p120-RasGAP protein is a negative regulator of the RAS/MAPK signaling pathway, which means it is involved in turning off these signals when they are not needed.

The exact role of p120-RasGAP is not fully understood. However, it appears to be essential for the normal development of the vascular system, which is the complex network of arteries, veins, and capillaries that carry blood to and from the heart.

Does the RASA1 gene share characteristics with other genes?

The RASA1 gene belongs to a family of genes called SH2 domain containing (SH2 domain containing).

A gene family is a group of genes that share important characteristics. Classifying individual genes into families helps researchers describe how genes are related to each other. For more information, see What are gene families? ( in the Handbook.

How are changes in the RASA1 gene related to health conditions?

capillary malformation-arteriovenous malformation syndrome - caused by mutations in the RASA1 gene

Several dozen mutations in the RASA1 gene have been found to cause capillary malformation-arteriovenous malformation syndrome (CM-AVM), which is a condition characterized by abnormalities of the vascular system. Most of the mutations responsible for CM-AVM prevent the production of functional p120-RasGAP protein. As a result, this protein is unavailable to control RAS/MAPK signaling. It is unclear how changes in this tightly regulated signaling pathway lead to the specific vascular abnormalities seen in people with CM-AVM.

Parkes Weber syndrome - caused by mutations in the RASA1 gene

Several mutations in the RASA1 gene have been identified in people with Parkes Weber syndrome. When the condition is caused by RASA1 gene mutations, affected individuals usually have multiple vascular abnormalities known as capillary malformations. Parkes Weber syndrome is also characterized by other abnormalities of the vascular system and overgrowth of one limb, most commonly a leg.

Like the RASA1 gene mutations that cause CM-AVM, the mutations responsible for Parkes Weber syndrome prevent the production of functional p120-RasGAP protein. A loss of this protein's activity disrupts the normal regulation of RAS/MAPK signaling. It is unclear how a lack of p120-RasGAP leads to the specific vascular abnormalities and limb overgrowth that occur in Parkes Weber syndrome.

cancers - associated with the RASA1 gene

At least three mutations in the RASA1 gene have been detected in a form of skin cancer called basal cell carcinoma. These mutations are described as somatic, which means they occur during a person's lifetime and are present only in the cells that become cancerous. Researchers suspect that the RASA1 gene mutations lead to a loss of p120-RasGAP protein function, which may allow RAS/MAPK signaling to proceed in an uncontrolled way. This unchecked RAS/MAPK signaling could lead to unregulated cell proliferation and the formation of a cancerous tumor. RASA1 gene mutations are found in only a small percentage of all basal cell carcinomas, and they are not thought to be a major cause of these cancers.

Where is the RASA1 gene located?

Cytogenetic Location: 5q13.3

Molecular Location on chromosome 5: base pairs 87,267,801 to 87,391,926

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

The RASA1 gene is located on the long (q) arm of chromosome 5 at position 13.3.

The RASA1 gene is located on the long (q) arm of chromosome 5 at position 13.3.

More precisely, the RASA1 gene is located from base pair 87,267,801 to base pair 87,391,926 on chromosome 5.

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

Where can I find additional information about RASA1?

You and your healthcare professional may find the following resources about RASA1 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 RASA1 gene or gene products?

  • DKFZp434N071
  • GAP
  • GTPase-activating protein
  • p120
  • p120GAP
  • p120RASGAP
  • RASA
  • ras GTPase-activating protein 1
  • RAS p21 protein activator (GTPase activating protein) 1
  • triphosphatase-activating protein

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

What glossary definitions help with understanding RASA1?

arteries ; arteriovenous ; cancer ; capillaries ; carcinoma ; cell ; cell proliferation ; cM ; differentiation ; gene ; malformation ; nucleus ; proliferation ; protein ; RAS ; syndrome ; tumor ; vascular ; veins

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


  • Boon LM, Mulliken JB, Vikkula M. RASA1: variable phenotype with capillary and arteriovenous malformations. Curr Opin Genet Dev. 2005 Jun;15(3):265-9. Review. (
  • Eerola I, Boon LM, Mulliken JB, Burrows PE, Dompmartin A, Watanabe S, Vanwijck R, Vikkula M. Capillary malformation-arteriovenous malformation, a new clinical and genetic disorder caused by RASA1 mutations. Am J Hum Genet. 2003 Dec;73(6):1240-9. Epub 2003 Nov 24. (
  • Friedman E, Gejman PV, Martin GA, McCormick F. Nonsense mutations in the C-terminal SH2 region of the GTPase activating protein (GAP) gene in human tumours. Nat Genet. 1993 Nov;5(3):242-7. (
  • Gene Review: RASA1-Related Disorders (
  • Kulkarni SV, Gish G, van der Geer P, Henkemeyer M, Pawson T. Role of p120 Ras-GAP in directed cell movement. J Cell Biol. 2000 Apr 17;149(2):457-70. (
  • NCBI Gene (
  • Revencu N, Boon LM, Mulliken JB, Enjolras O, Cordisco MR, Burrows PE, Clapuyt P, Hammer F, Dubois J, Baselga E, Brancati F, Carder R, Quintal JM, Dallapiccola B, Fischer G, Frieden IJ, Garzon M, Harper J, Johnson-Patel J, Labrèze C, Martorell L, Paltiel HJ, Pohl A, Prendiville J, Quere I, Siegel DH, Valente EM, Van Hagen A, Van Hest L, Vaux KK, Vicente A, Weibel L, Chitayat D, Vikkula M. Parkes Weber syndrome, vein of Galen aneurysmal malformation, and other fast-flow vascular anomalies are caused by RASA1 mutations. Hum Mutat. 2008 Jul;29(7):959-65. doi: 10.1002/humu.20746. (


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: August 2011
Published: February 1, 2016