Skip navigation

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

URL of this page:

ASXL1 gene

ASXL transcriptional regulator 1

Normal Function

The ASXL1 gene provides instructions for making a protein that is involved in a process known as chromatin remodeling. Chromatin is the complex of DNA and proteins that packages DNA into chromosomes. The structure of chromatin can be changed (remodeled) to alter how tightly DNA is packaged. When DNA is tightly packed, gene activity (expression) is lower than when DNA is loosely packed.

Through its role in chromatin remodeling, the ASXL1 protein regulates the expression of many genes, including a group of genes known as HOX genes, which play important roles in development before birth. The ASXL1 protein can turn on (activate) or turn off (repress) HOX genes depending on when they are needed.

The ASXL1 protein may have an additional role in gene regulation by signaling to molecules to add a methyl group (a process called methylation) to an area near a gene called the promoter region, which controls gene activity. When a promoter region is methylated, gene activity is repressed, and when a promoter region is not methylated, the gene is active.

Health Conditions Related to Genetic Changes

Bohring-Opitz syndrome

More than 20 mutations in the ASXL1 gene have been found to cause Bohring-Opitz syndrome, a condition that causes abnormal head size and shape, distinctive facial features, joint abnormalities, intellectual disability, and other signs and symptoms. Most of the ASXL1 gene mutations that cause Bohring-Opitz syndrome create a premature stop signal in the instructions for making the ASXL1 protein, resulting in either an abnormally short, nonfunctional protein or a complete lack of ASXL1 protein. These ASXL1 gene mutations are described as "loss-of-function" because they reduce the amount of functional ASXL1 protein available, which likely disrupts the regulation of the activity of HOX genes and other genes during development. Altered activity of HOX genes probably leads to the neurological and physical features of this condition.

More About This Health Condition

Systemic mastocytosis

MedlinePlus Genetics provides information about Systemic mastocytosis

More About This Health Condition


Mutations in the ASXL1 gene have been associated with cancerous conditions of blood-forming cells, such as acute myeloid leukemia, chronic myelomonocytic leukemia, and myelodysplastic syndrome. These mutations are somatic, which means they are acquired during a person's lifetime and are present only in cells that give rise to cancer.

The mutations associated with these conditions are likely "gain-of-function," which means that they lead to an overactive ASXL1 protein. Researchers believe that the overactive ASXL1 protein leads to poor regulation of gene activity. It is unclear how this altered gene regulation plays a role in the development of cancer, but it is likely that overactive genes promote the growth of cancers by allowing abnormal blood cells to grow and divide uncontrollably.

The ASXL1 gene mutations involved in these cancers are different from the ones that cause Bohring-Opitz syndrome (described above). People with Bohring-Opitz syndrome are not thought to have an increased risk of developing cancer.

Other Names for This Gene

  • additional sex combs like 1
  • additional sex combs like 1, transcriptional regulator
  • additional sex combs like transcriptional regulator 1
  • KIAA0978
  • putative Polycomb group protein ASXL1 isoform 1
  • putative Polycomb group protein ASXL1 isoform 2

Additional Information & Resources

Tests Listed in the Genetic Testing Registry

Scientific Articles on PubMed

Catalog of Genes and Diseases from OMIM

Gene and Variant Databases


  • Aravind L, Iyer LM. The HARE-HTH and associated domains: novel modules in the coordination of epigenetic DNA and protein modifications. Cell Cycle. 2012 Jan 1;11(1):119-31. doi: 10.4161/cc.11.1.18475. Epub 2012 Jan 1. Citation on PubMed or Free article on PubMed Central
  • Bohring A, Oudesluijs GG, Grange DK, Zampino G, Thierry P. New cases of Bohring-Opitz syndrome, update, and critical review of the literature. Am J Med Genet A. 2006 Jun 15;140(12):1257-63. doi: 10.1002/ajmg.a.31265. Citation on PubMed
  • Hoischen A, van Bon BW, Rodriguez-Santiago B, Gilissen C, Vissers LE, de Vries P, Janssen I, van Lier B, Hastings R, Smithson SF, Newbury-Ecob R, Kjaergaard S, Goodship J, McGowan R, Bartholdi D, Rauch A, Peippo M, Cobben JM, Wieczorek D, Gillessen-Kaesbach G, Veltman JA, Brunner HG, de Vries BB. De novo nonsense mutations in ASXL1 cause Bohring-Opitz syndrome. Nat Genet. 2011 Jun 26;43(8):729-31. doi: 10.1038/ng.868. Citation on PubMed
  • Inoue D, Matsumoto M, Nagase R, Saika M, Fujino T, Nakayama KI, Kitamura T. Truncation mutants of ASXL1 observed in myeloid malignancies are expressed at detectable protein levels. Exp Hematol. 2016 Mar;44(3):172-6.e1. doi: 10.1016/j.exphem.2015.11.011. Epub 2015 Dec 15. Citation on PubMed
  • Magini P, Della Monica M, Uzielli ML, Mongelli P, Scarselli G, Gambineri E, Scarano G, Seri M. Two novel patients with Bohring-Opitz syndrome caused by de novo ASXL1 mutations. Am J Med Genet A. 2012 Apr;158A(4):917-21. doi: 10.1002/ajmg.a.35265. Epub 2012 Mar 14. Citation on PubMed
  • Russell B, Johnston JJ, Biesecker LG, Kramer N, Pickart A, Rhead W, Tan WH, Brownstein CA, Kate Clarkson L, Dobson A, Rosenberg AZ, Vergano SA, Helm BM, Harrison RE, Graham JM Jr. Clinical management of patients with ASXL1 mutations and Bohring-Opitz syndrome, emphasizing the need for Wilms tumor surveillance. Am J Med Genet A. 2015 Sep;167A(9):2122-31. doi: 10.1002/ajmg.a.37131. Epub 2015 Apr 29. Citation on PubMed or Free article on PubMed Central

The information on this site should not be used as a substitute for professional medical care or advice. Contact a health care provider if you have questions about your health.