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KIF21A gene
Reviewed by Medicinsk Expert•Last updated: 2026-10-22•Gene

KIF21A gene

The KIF21A gene provides instructions for a protein that regulates microtubule growth, which is critical for the proper development of neurons.

Normal Function

The KIF21A gene provides instructions for making a protein that is part of the kinesin family. Many proteins in the kinesin family are essential for the transport of materials within cells. Kinesin proteins function like freight trains that transport cargo along a track-like system made from structures called microtubules. Some kinesins also help maintain microtubules. As well as functioning like a track, microtubules make up the structural framework of cells and help cells move.

The KIF21A protein is found in nerve cells (neurons) and many other cell types. Researchers believe that this protein plays an important role in neuron development by helping control the growth of microtubules. By blocking microtubule growth at critical times, the KIF21A protein may help direct the path of neuron extensions known as axons so they can reach their correct locations. Once in the right position, axons relay messages to and from the brain to control muscle movement and detect sensations such as touch, pain, and heat.

For proper neuron development, the KIF21A protein must be turned on and off at particular times. When a segment of the protein known as the regulatory region interacts with another segment of the protein known as the motor domain, the protein is turned off (which is known as autoinhibition).

Health Conditions Related to Genetic Changes

Congenital fibrosis of the extraocular muscles

At least 12 mutations in the KIF21A gene have been identified in people with congenital fibrosis of the extraocular muscles (CFEOM). These mutations cause the most common form of the disorder, CFEOM1, and are a rare cause of another form of the condition called CFEOM3. Individuals with CFEOM are unable to move their eyes normally. They have difficulty looking upward or, less commonly, side-to-side, and most also have droopy eyelids (ptosis). In addition, people with CFEOM3 can have intellectual disability or other neurological problems.

Each of the known KIF21A gene mutations changes a single protein building block (amino acid) in the KIF21A protein. Most of these changes occur in the regulatory region of the protein. These mutations alter the protein's structure, which interferes with its ability to turn itself off. As a result, the KIF21A protein is always on (constitutively active) and cannot regulate microtubule growth. Without proper control of microtubule elongation, the axons of nerves develop abnormally and do not reach the muscles they control. Nerves in the head and face (cranial nerves) that control muscles that surround the eyes (extraocular muscles) are particularly affected. Problems with cranial nerve development impair extraocular muscle function, resulting in the characteristic features of CFEOM such as restricted eye movement and droopy eyelids.

Other Names for This Gene

  • CFEOM
  • CFEOM1
  • DKFZp779C159
  • FEOM
  • FEOM1
  • Fibrosis of extraocular muscles, congenital, 1, autosomal dominant
  • fibrosis of the extraocular muscles, congenital, 1
  • FLJ20052
  • KI21A_HUMAN
  • KIAA1708
  • KIF2
  • KIF21A variant protein
  • Kinesin-like protein KIF2
  • Kinesin-like protein KIF21A
  • NY-REN-62 antigen
  • Renal carcinoma antigen NY-REN-62

Frequently Asked Questions

CFEOM is characterized by severe limitations in eye movement, often resulting in the eyes being fixed in a downward position (ptosis) and an inability to look up or move the eyes side-to-side. Patients typically present with these symptoms at birth, and the condition is generally non-progressive, meaning the eye position does not worsen over time but remains fixed. How does the KIF21A protein regulate the development of nerve pathways in the brain?::The KIF21A protein helps control the growth of microtubules within neurons. By blocking microtubule growth at specific times, it directs the path of axons, ensuring they reach their correct destinations in the body. This precise guidance is essential for establishing proper connections for muscle movement and sensory perception. Is CFEOM caused by KIF21A mutations inherited in a predictable pattern?::Yes, CFEOM caused by KIF21A mutations is typically inherited in an autosomal dominant pattern. This means that only one copy of the altered gene in each cell is sufficient to cause the condition. However, many cases arise from new (de novo) mutations in the gene that did not occur in the family's previous generations, so a parent may not have the condition. Can the eye movement issues associated with KIF21A mutations be corrected with surgery?::Surgical intervention is often used to manage the cosmetic and functional aspects of CFEOM, such as correcting drooping eyelids (ptosis) or improving the alignment of the eyes. While surgery can improve the appearance and reduce double vision in some cases, it cannot restore full, normal eye movement because the underlying issue is the structural fibrosis of the muscles and the developmental error in the nerve pathways.
Source: MedlinePlus, National Library of Medicine

MedlinePlus brings together authoritative health information from the National Library of Medicine (NLM), the National Institutes of Health (NIH), and other government agencies and health-related organizations.

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