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


Reviewed March 2009

What is the official name of the KIF21A gene?

The official name of this gene is “kinesin family member 21A.”

KIF21A is the gene's official symbol. The KIF21A gene is also known by other names, listed below.

What is the normal function of the KIF21A gene?

The KIF21A gene provides instructions for making a protein called kinesin family member 21A. Proteins in the kinesin family are essential for the transport of materials within cells. Kinesin proteins function like freight trains that transport cargo, and their structure is suited for this cargo-carrying function. One end of the protein, called the motor domain, provides power to move the protein and its cargo along a track-like system made from structures called microtubules. The other end of the protein attaches (binds) to specific cargo, such as groups of proteins, for transport. The two ends of each kinesin are connected by a flexible region known as the stalk.

Kinesin family member 21A is found in developing nerve cells (neurons). Researchers believe that this protein carries cargo that is needed for the normal development and function of nerves in the head and face. In particular, this kinesin plays a critical role in the development of cranial nerve III, which emerges from the brain and controls several of the muscles that surround the eyes (extraocular muscles). These muscles direct eye movement and determine the position of the eyes.

Does the KIF21A gene share characteristics with other genes?

The KIF21A gene belongs to a family of genes called KIF (kinesins). It also belongs to a family of genes called WDR (WD repeat 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 KIF21A gene related to health conditions?

congenital fibrosis of the extraocular muscles - caused by mutations in the KIF21A gene

At least 11 mutations in the KIF21A gene have been identified in people with congenital fibrosis of the extraocular muscles. These mutations cause the most common form of the disorder, CFEOM1, and are a rare cause of another form of the condition called CFEOM3.

Each of the known KIF21A mutations changes a single protein building block (amino acid) in kinesin family member 21A. Most of these changes occur in the stalk region of the protein. These mutations alter the protein's structure, which likely interferes with its ability to transport cargo within neurons. As a result, several cranial nerves and the extraocular muscles they control do not develop normally. Abnormal development and function of these muscles leads to the characteristic features of congenital fibrosis of the extraocular muscles, including restricted eye movement and related problems with vision.

Where is the KIF21A gene located?

Cytogenetic Location: 12q12

Molecular Location on chromosome 12: base pairs 39,293,228 to 39,443,390

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

The KIF21A gene is located on the long (q) arm of chromosome 12 at position 12.

The KIF21A gene is located on the long (q) arm of chromosome 12 at position 12.

More precisely, the KIF21A gene is located from base pair 39,293,228 to base pair 39,443,390 on chromosome 12.

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

Where can I find additional information about KIF21A?

You and your healthcare professional may find the following resources about KIF21A 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 KIF21A gene or gene products?

  • CFEOM1
  • DKFZp779C159
  • FEOM
  • FEOM1
  • Fibrosis of extraocular muscles, congenital, 1, autosomal dominant
  • fibrosis of the extraocular muscles, congenital, 1
  • FLJ20052
  • KIAA1708
  • KIF2
  • KIF21A variant protein
  • Kinesin-like protein KIF2
  • Kinesin-like protein KIF21A
  • NY-REN-62 antigen
  • Renal carcinoma antigen NY-REN-62

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

What glossary definitions help with understanding KIF21A?

amino acid ; autosomal ; autosomal dominant ; carcinoma ; congenital ; cranial nerves ; domain ; extraocular muscles ; fibrosis ; gene ; motor ; protein ; renal

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


  • Chan WM, Andrews C, Dragan L, Fredrick D, Armstrong L, Lyons C, Geraghty MT, Hunter DG, Yazdani A, Traboulsi EI, Pott JW, Gutowski NJ, Ellard S, Young E, Hanisch F, Koc F, Schnall B, Engle EC. Three novel mutations in KIF21A highlight the importance of the third coiled-coil stalk domain in the etiology of CFEOM1. BMC Genet. 2007 May 18;8:26. (
  • Demer JL, Clark RA, Engle EC. Magnetic resonance imaging evidence for widespread orbital dysinnervation in congenital fibrosis of extraocular muscles due to mutations in KIF21A. Invest Ophthalmol Vis Sci. 2005 Feb;46(2):530-9. (
  • Heidary G, Engle EC, Hunter DG. Congenital fibrosis of the extraocular muscles. Semin Ophthalmol. 2008 Jan-Feb;23(1):3-8. doi: 10.1080/08820530701745181. Review. (
  • Lu S, Zhao C, Zhao K, Li N, Larsson C. Novel and recurrent KIF21A mutations in congenital fibrosis of the extraocular muscles type 1 and 3. Arch Ophthalmol. 2008 Mar;126(3):388-94. doi: 10.1001/archopht.126.3.388. (
  • Marszalek JR, Weiner JA, Farlow SJ, Chun J, Goldstein LS. Novel dendritic kinesin sorting identified by different process targeting of two related kinesins: KIF21A and KIF21B. J Cell Biol. 1999 May 3;145(3):469-79. (
  • NCBI Gene (
  • Tiab L, d'Allèves Manzi V, Borruat FX, Munier F, Schorderet D. Mutation analysis of KIF21A in congenital fibrosis of the extraocular muscles (CFEOM) patients. Ophthalmic Genet. 2004 Dec;25(4):241-6. (
  • Yamada K, Andrews C, Chan WM, McKeown CA, Magli A, de Berardinis T, Loewenstein A, Lazar M, O'Keefe M, Letson R, London A, Ruttum M, Matsumoto N, Saito N, Morris L, Del Monte M, Johnson RH, Uyama E, Houtman WA, de Vries B, Carlow TJ, Hart BL, Krawiecki N, Shoffner J, Vogel MC, Katowitz J, Goldstein SM, Levin AV, Sener EC, Ozturk BT, Akarsu AN, Brodsky MC, Hanisch F, Cruse RP, Zubcov AA, Robb RM, Roggenkäemper P, Gottlob I, Kowal L, Battu R, Traboulsi EI, Franceschini P, Newlin A, Demer JL, Engle EC. Heterozygous mutations of the kinesin KIF21A in congenital fibrosis of the extraocular muscles type 1 (CFEOM1). Nat Genet. 2003 Dec;35(4):318-21. Epub 2003 Nov 2. (
  • Yamada K, Chan WM, Andrews C, Bosley TM, Sener EC, Zwaan JT, Mullaney PB, Oztürk BT, Akarsu AN, Sabol LJ, Demer JL, Sullivan TJ, Gottlob I, Roggenkäemper P, Mackey DA, De Uzcategui CE, Uzcategui N, Ben-Zeev B, Traboulsi EI, Magli A, de Berardinis T, Gagliardi V, Awasthi-Patney S, Vogel MC, Rizzo JF 3rd, Engle EC. Identification of KIF21A mutations as a rare cause of congenital fibrosis of the extraocular muscles type 3 (CFEOM3). Invest Ophthalmol Vis Sci. 2004 Jul;45(7):2218-23. (


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: March 2009
Published: February 8, 2016