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


Reviewed April 2010

What is the official name of the HAX1 gene?

The official name of this gene is “HCLS1 associated protein X-1.”

HAX1 is the gene's official symbol. The HAX1 gene is also known by other names, listed below.

What is the normal function of the HAX1 gene?

The HAX1 gene provides instructions for making a protein called HS-1-associated protein X-1 (HAX-1). This protein is involved in the regulation of apoptosis, which is the process by which cells self-destruct when they are damaged or no longer needed. Apoptosis is a common process that occurs throughout life. The HAX-1 protein is also thought to be involved in cell movement (migration). The HAX-1 protein is found primarily in the mitochondria, the energy-producing centers within cells.

Different versions of the HAX-1 protein can be produced from the HAX1 gene by a mechanism called alternative splicing. This mechanism produces different version of the protein by cutting and rearranging the genetic instructions in different ways. The purpose of these multiple versions of the HAX-1 protein is unclear.

How are changes in the HAX1 gene related to health conditions?

severe congenital neutropenia - caused by mutations in the HAX1 gene

At least 10 mutations in the HAX1 gene have been found to cause severe congenital neutropenia, a condition characterized by a shortage (deficiency) of neutrophils. Neutrophils are a type of white blood cell that play a role in inflammation and in fighting infection. Most of the mutations that cause severe congenital neutropenia change single protein building blocks (amino acids) in the HAX-1 protein. HAX1 gene mutations that cause severe congenital neutropenia result in the production of a nonfunctional HAX-1 protein. A lack of functional HAX-1 protein disrupts regulation of apoptosis, leading to the premature death of neutrophils. A deficiency of neutrophils results in recurrent infections, episodes of inflammation, and other immune problems in people with severe congenital neutropenia.

People with certain HAX1 gene mutations have neurological problems such as seizures and developmental delay in addition to severe congenital neutropenia. These mutations disrupt two of the alternatively spliced versions of the HAX-1 protein. The gene mutations that lead to severe congenital neutropenia alone disrupt only one version of the HAX-1 protein. It is unclear how nonfunctional HAX-1 proteins cause neurological features seen in some affected individuals.

Where is the HAX1 gene located?

Cytogenetic Location: 1q21.3

Molecular Location on chromosome 1: base pairs 154,272,563 to 154,275,875

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

The HAX1 gene is located on the long (q) arm of chromosome 1 at position 21.3.

The HAX1 gene is located on the long (q) arm of chromosome 1 at position 21.3.

More precisely, the HAX1 gene is located from base pair 154,272,563 to base pair 154,275,875 on chromosome 1.

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

Where can I find additional information about HAX1?

You and your healthcare professional may find the following resources about HAX1 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 HAX1 gene or gene products?

  • HAX-1
  • HCLS1-associated protein X-1
  • HS1-associating protein X-1
  • HS1 binding protein
  • HS1-binding protein 1
  • HS1BP1
  • HSP1BP-1

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

What glossary definitions help with understanding HAX1?

acids ; alternative splicing ; apoptosis ; cell ; congenital ; deficiency ; developmental delay ; gene ; infection ; inflammation ; mitochondria ; neurological ; neutropenia ; neutrophils ; protein ; splicing

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


  • Boztug K, Klein C. Novel genetic etiologies of severe congenital neutropenia. Curr Opin Immunol. 2009 Oct;21(5):472-80. doi: 10.1016/j.coi.2009.09.003. Epub 2009 Sep 24. Review. (
  • Fadeel B, Grzybowska E. HAX-1: a multifunctional protein with emerging roles in human disease. Biochim Biophys Acta. 2009 Oct;1790(10):1139-48. doi: 10.1016/j.bbagen.2009.06.004. Epub 2009 Jun 12. Review. (
  • NCBI Gene (
  • Xia J, Bolyard AA, Rodger E, Stein S, Aprikyan AA, Dale DC, Link DC. Prevalence of mutations in ELANE, GFI1, HAX1, SBDS, WAS and G6PC3 in patients with severe congenital neutropenia. Br J Haematol. 2009 Nov;147(4):535-42. doi: 10.1111/j.1365-2141.2009.07888.x. Epub 2009 Sep 22. (
  • Zeidler C, Germeshausen M, Klein C, Welte K. Clinical implications of ELA2-, HAX1-, and G-CSF-receptor (CSF3R) mutations in severe congenital neutropenia. Br J Haematol. 2009 Feb;144(4):459-67. doi: 10.1111/j.1365-2141.2008.07425.x. Epub 2008 Dec 10. Review. (


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: April 2010
Published: February 8, 2016