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


Reviewed February 2010

What is the official name of the SMC1A gene?

The official name of this gene is “structural maintenance of chromosomes 1A.”

SMC1A is the gene's official symbol. The SMC1A gene is also known by other names, listed below.

What is the normal function of the SMC1A gene?

The SMC1A gene provides instructions for making a protein that is part of a family called the structural maintenance of chromosomes (SMC) family. Within the nucleus, SMC proteins help regulate the structure and organization of chromosomes.

The protein produced from the SMC1A gene (which is usually called the SMC1 protein) helps control the activity of chromosomes during cell division. Before cells divide, they must copy all of their chromosomes. The copied DNA from each chromosome is arranged into two identical structures, called sister chromatids, which are attached to one another during the early stages of cell division. The SMC1 protein is part of a protein group called the cohesion complex that holds the sister chromatids together.

Researchers believe that the SMC1 protein also plays important roles in stabilizing cells' genetic information, repairing damaged DNA, and controlling the activity of certain genes that are essential for normal development.

Does the SMC1A gene share characteristics with other genes?

The SMC1A gene belongs to a family of genes called SMC (structural maintenance of chromosomes proteins).

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 SMC1A gene related to health conditions?

Cornelia de Lange syndrome - caused by mutations in the SMC1A gene

More than 20 mutations in the SMC1A gene have been identified in people with Cornelia de Lange syndrome. These mutations account for about 5 percent of all cases of this condition.

Most of the SMC1A gene mutations responsible for Cornelia de Lange syndrome change single protein building blocks (amino acids) used to make the SMC1 protein. These genetic changes alter the structure and function of the protein, disrupting its ability to regulate genes involved in development. These changes in gene regulation are likely responsible for the developmental problems characteristic of Cornelia de Lange syndrome.

Studies suggest that mutations in the SMC1A gene usually cause a form of Cornelia de Lange syndrome with relatively mild features. Compared to mutations in the NIPBL gene, which are a more common cause of the disorder, SMC1A gene mutations tend to cause less significant delays in development and growth and are less likely to cause major birth defects.

Where is the SMC1A gene located?

Cytogenetic Location: Xp11.22-p11.21

Molecular Location on the X chromosome: base pairs 53,374,148 to 53,422,727

The SMC1A gene is located on the short (p) arm of the X chromosome between positions 11.22 and 11.21.

The SMC1A gene is located on the short (p) arm of the X chromosome between positions 11.22 and 11.21.

More precisely, the SMC1A gene is located from base pair 53,374,148 to base pair 53,422,727 on the X chromosome.

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

Where can I find additional information about SMC1A?

You and your healthcare professional may find the following resources about SMC1A 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 SMC1A gene or gene products?

  • DXS423E
  • KIAA0178
  • segregation of mitotic chromosomes 1
  • SMC1
  • SMC1-alpha
  • SMC1L1
  • SMCB

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

What glossary definitions help with understanding SMC1A?

acids ; cell ; cell division ; chromatid ; chromosome ; cohesion ; DNA ; gene ; gene regulation ; nucleus ; protein ; segregation ; sister chromatid ; sister chromatid cohesion ; syndrome

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


  • Borck G, Zarhrate M, Bonnefont JP, Munnich A, Cormier-Daire V, Colleaux L. Incidence and clinical features of X-linked Cornelia de Lange syndrome due to SMC1L1 mutations. Hum Mutat. 2007 Feb;28(2):205-6. (
  • Deardorff MA, Kaur M, Yaeger D, Rampuria A, Korolev S, Pie J, Gil-Rodríguez C, Arnedo M, Loeys B, Kline AD, Wilson M, Lillquist K, Siu V, Ramos FJ, Musio A, Jackson LS, Dorsett D, Krantz ID. Mutations in cohesin complex members SMC3 and SMC1A cause a mild variant of cornelia de Lange syndrome with predominant mental retardation. Am J Hum Genet. 2007 Mar;80(3):485-94. Epub 2007 Jan 17. (
  • Gene Review: Cornelia de Lange Syndrome (
  • Gervasini C, Russo S, Cereda A, Parenti I, Masciadri M, Azzollini J, Melis D, Aravena T, Doray B, Ferrarini A, Garavelli L, Selicorni A, Larizza L. Cornelia de Lange individuals with new and recurrent SMC1A mutations enhance delineation of mutation repertoire and phenotypic spectrum. Am J Med Genet A. 2013 Nov;161A(11):2909-19. doi: 10.1002/ajmg.a.36252. Epub 2013 Oct 2. (
  • Liu J, Feldman R, Zhang Z, Deardorff MA, Haverfield EV, Kaur M, Li JR, Clark D, Kline AD, Waggoner DJ, Das S, Jackson LG, Krantz ID. SMC1A expression and mechanism of pathogenicity in probands with X-Linked Cornelia de Lange syndrome. Hum Mutat. 2009 Nov;30(11):1535-42. doi: 10.1002/humu.21095. (
  • Mannini L, Cucco F, Quarantotti V, Krantz ID, Musio A. Mutation spectrum and genotype-phenotype correlation in Cornelia de Lange syndrome. Hum Mutat. 2013 Dec;34(12):1589-96. doi: 10.1002/humu.22430. Epub 2013 Sep 16. Review. (
  • Mannini L, Liu J, Krantz ID, Musio A. Spectrum and consequences of SMC1A mutations: the unexpected involvement of a core component of cohesin in human disease. Hum Mutat. 2010 Jan;31(1):5-10. doi: 10.1002/humu.21129. Review. (
  • Musio A, Selicorni A, Focarelli ML, Gervasini C, Milani D, Russo S, Vezzoni P, Larizza L. X-linked Cornelia de Lange syndrome owing to SMC1L1 mutations. Nat Genet. 2006 May;38(5):528-30. Epub 2006 Apr 9. (
  • NCBI Gene (
  • Revenkova E, Focarelli ML, Susani L, Paulis M, Bassi MT, Mannini L, Frattini A, Delia D, Krantz I, Vezzoni P, Jessberger R, Musio A. Cornelia de Lange syndrome mutations in SMC1A or SMC3 affect binding to DNA. Hum Mol Genet. 2009 Feb 1;18(3):418-27. doi: 10.1093/hmg/ddn369. Epub 2008 Nov 7. (


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: February 2010
Published: September 1, 2015