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FKTN

fukutin

The FKTN gene provides instructions for producing the fukutin enzyme, which is critical for a protein modification process called glycosylation, particularly impacting muscle and brain development. FKTN is a gene that encodes the fukutin enzyme, playing a key role in the glycosylation of alpha-dystroglycan.

Chromosome 9q31.2 Autosomal recessive HGNC:3622 Tier C
FKTN 9q31.2 p arm q arm 9

FKTN is located on the long (q) arm of chromosome 9, at band 9q31.2. Arm ratio per GRCh38 - banding schematic.

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Clinical tests that include this

Carrier Screening panel
FKTN is 1 of 1,008 genes on this panel
Expanded carrier screening for recessive and X-linked conditions

Overview

The FKTN gene is responsible for encoding the fukutin enzyme, which is found in many body tissues, with high concentrations in the heart, brain, and skeletal muscles. This enzyme is primarily located within the Golgi apparatus, where it contributes to the modification of newly synthesised proteins.

Fukutin's role in protein modification is crucial for the proper function of key structural proteins, such as alpha-dystroglycan, which is vital for muscle integrity and neurological development.

What the gene does

Fukutin plays an integral part in protein glycosylation, a chemical process that involves adding sugar molecules to specific proteins. Specifically, fukutin works alongside other enzymes to attach ribitol phosphate molecules to existing sugar chains on the alpha-dystroglycan protein. This glycosylation is fundamental for alpha-dystroglycan to function correctly.

Alpha-dystroglycan acts as an anchor, connecting the internal structural framework of cells (cytoskeleton) to the surrounding extracellular matrix. In skeletal muscles, this connection is vital for stabilising and protecting muscle fibres. In the brain, alpha-dystroglycan helps guide the movement of neurons during early developmental stages.

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Chromosome location

The FKTN gene is situated on chromosome 9 at position q31.2. This location refers to the long arm of chromosome 9, specifically within band 31.2.

Protein structure

The FKTN gene encodes a protein composed of 461 amino acids. A specific region spanning amino acids 6-27 has been identified as required and sufficient for interaction with POMGNT1, highlighting a key functional area of the fukutin enzyme.

Domain map · 461 amino acids
Required and sufficient for interaction with POMGNT1 (6–27)Required and sufficien6–271~231461
Region - functional region
🧬 Explore 3D structure on AlphaFold
UniProt:O75072Length:461 aaStructure:AlphaFold

Key variants

Variants within the FKTN gene can alter the fukutin enzyme's function, impacting the crucial glycosylation process. These genetic changes are typically inherited in an autosomal recessive manner. Such variants can lead to a spectrum of conditions, primarily affecting muscle and brain development.

The table below shows the top 10 pathogenic or likely-pathogenic variants currently classified in ClinVar for FKTN.
View all on ClinVar →

Sample of pathogenic variants

10 pathogenic / likely-pathogenic variants from ClinVar, ranked by review status (expert-panel-reviewed first). This is a sample; recurrent founder variants in a specific population may not appear here - see the full ClinVar listing via the link above.

Variant (HGVS) Protein change Classification Evidence Associated condition
c.1045-6C>G
single nucleotide variant
 - Pathogenic ★★☆☆ Walker-Warburg congenital muscular dystrophy
c.1117G>T
single nucleotide variant
 p.Glu373Ter Pathogenic/Likely pathogenic ★★☆☆ Walker-Warburg congenital muscular dystrophy
c.1167del
Deletion
 p.Lys389fs Pathogenic/Likely pathogenic ★★☆☆ Cardiovascular phenotype
c.1272dup
Duplication
 p.Lys425Ter Pathogenic/Likely pathogenic ★★☆☆ Walker-Warburg congenital muscular dystrophy
c.164G>A
single nucleotide variant
 p.Trp55Ter Pathogenic/Likely pathogenic ★★☆☆ Cardiomyopathy
c.180dup
Duplication
 p.Phe61fs Pathogenic ★★☆☆ Walker-Warburg congenital muscular dystrophy
c.540del
Deletion
 p.Ser180fs Pathogenic/Likely pathogenic ★★☆☆ Walker-Warburg congenital muscular dystrophy
c.78C>G
single nucleotide variant
 p.Tyr26Ter Pathogenic ★★☆☆ Muscular dystrophy-dystroglycanopathy (congenital with brain and eye anomalies), type A, 4
c.82_83insGT
Insertion
 p.Tyr28fs Pathogenic/Likely pathogenic ★★☆☆ Walker-Warburg congenital muscular dystrophy
c.910+1G>C
single nucleotide variant
 - Pathogenic/Likely pathogenic ★★☆☆ Walker-Warburg congenital muscular dystrophy

Evidence stars indicate ClinVar review status. Individual variant interpretation should always be performed by a qualified clinical laboratory - many variants remain classified as Variants of Uncertain Significance (VUS) pending more research.

Associated conditions

Pathogenic variants in the FKTN gene are associated with several forms of congenital muscular dystrophy. These include Fukuyama congenital muscular dystrophy, which primarily affects individuals of Japanese ancestry, and Walker-Warburg syndrome, a more severe form characterised by significant eye and brain abnormalities. Variants in FKTN have also been linked to muscular dystrophy-dystroglycanopathy, type B4 (MDDGB4), which typically presents with muscle weakness and delayed motor skill development.

No disease links recorded for this gene in our reference set.

Inheritance pattern

Conditions caused by pathogenic FKTN variants typically follow autosomal recessive inheritance.

♀ Carrier parent 1 altered copy ♂ Carrier parent 1 altered copy Affected Carrier Carrier Unaffected Affected Carrier Unaffected Circles = females · Squares = males

When both parents are carriers, each child has a 25% chance of being affected, 50% of being a carrier, and 25% of being unaffected.

Carrier frequency by population How common is heterozygous FKTN carrier status across ancestry groups?

UK clinical status

In the UK, the FKTN gene is included in several NHS Genomic Medicine Service national testing panels via PanelApp. These include panels for conditions such as Arthrogryposis, Congenital muscular dystrophy (R79), Foetal anomalies (R21), Hydrocephalus (R86), and Paediatric or syndromic cardiomyopathy (R135).

Green-listed
High evidence · clinically actionable in NHS testing
Included in NHS GMS signed-off panels
Arthrogryposis · R83 NHS GMS → Congenital muscular dystrophy · R79 NHS GMS → Fetal anomalies · R21 NHS GMS → Hydrocephalus · R86 NHS GMS → Likely inborn error of metabolism · R98 NHS GMS → Limb girdle muscular dystrophies, myofibrillar myopathies and distal myopathies · R82 NHS GMS → Paediatric or syndromic cardiomyopathy · R135 NHS GMS → Structural eye disease · R36 NHS GMS →
NHS Genomic Medicine Service Jeen carrier screening

Sources: NHS GMS PanelApp · Genomics England PanelApp · NHS National Genomic Test Directory

Frequently asked questions

What is the primary function of the FKTN gene?

The FKTN gene provides instructions for the fukutin enzyme, which is crucial for the glycosylation of proteins like alpha-dystroglycan. This process is essential for muscle stability and brain development.

What conditions are associated with variants in the FKTN gene?

Variants in the FKTN gene are linked to several congenital muscular dystrophies, including Fukuyama congenital muscular dystrophy, Walker-Warburg syndrome, and muscular dystrophy-dystroglycanopathy, type B4 (MDDGB4).

How is alpha-dystroglycan related to the FKTN gene?

Alpha-dystroglycan requires modification by the fukutin enzyme to function correctly. This protein helps anchor the cell's internal structure to the extracellular matrix, protecting muscle fibres and guiding neuron migration in the brain.

References

  1. Kanagawa M, Kobayashi K, Tajiri M. Identification of a Post-translational Modification with Ribitol-Phosphate and Its Defect in Muscular Dystrophy. Cell reports. 2016. PMID: 26923585
  2. Gerin I, Ury B, Breloy I. ISPD produces CDP-ribitol used by FKTN and FKRP to transfer ribitol phosphate onto α-dystroglycan. Nature communications. 2016. PMID: 27194101
  3. Yis U, Uyanik G, Heck PB. Fukutin mutations in non-Japanese patients with congenital muscular dystrophy: less severe mutations predominate in patients with a non-Walker-Warburg phenotype. Neuromuscular disorders : NMD. 2011. PMID: 20961758
  4. Cotarelo RP, Valero MC, Prados B. Two new patients bearing mutations in the fukutin gene confirm the relevance of this gene in Walker-Warburg syndrome. Clinical genetics. 2008. PMID: 18177472
  5. Saito Y, Yamamoto T, Mizuguchi M. Altered glycosylation of alpha-dystroglycan in neurons of Fukuyama congenital muscular dystrophy brains. Brain research. 2006. PMID: 16466646
  6. Murakami T, Hayashi YK, Noguchi S. Fukutin gene mutations cause dilated cardiomyopathy with minimal muscle weakness. Annals of neurology. 2006. PMID: 17036286
  7. Godfrey C, Escolar D, Brockington M. Fukutin gene mutations in steroid-responsive limb girdle muscular dystrophy. Annals of neurology. 2006. PMID: 17044012
  8. Toda T, Kobayashi K, Takeda S. Fukuyama-type congenital muscular dystrophy (FCMD) and alpha-dystroglycanopathy. Congenital anomalies. 2003. PMID: 12893968
  9. de Bernabé DB, van Bokhoven H, van Beusekom E. A homozygous nonsense mutation in the fukutin gene causes a Walker-Warburg syndrome phenotype. Journal of medical genetics. 2003. PMID: 14627679
  10. Hayashi YK, Ogawa M, Tagawa K. Selective deficiency of alpha-dystroglycan in Fukuyama-type congenital muscular dystrophy. Neurology. 2001. PMID: 11445638
  11. Kondo-Iida E, Kobayashi K, Watanabe M. Novel mutations and genotype-phenotype relationships in 107 families with Fukuyama-type congenital muscular dystrophy (FCMD). Human molecular genetics. 1999. PMID: 10545611
Educational content. This page is not medical or genetic advice, is not individually reviewed by a clinician for each reader, and should not replace a consultation with a qualified healthcare professional or genetic counsellor. If you are considering genetic testing or acting on a test result, book a consultation.
Data sources Last updated 27 September 2026. Content compiled from HGNC · MedlinePlus Genetics · ClinGen · Genomics England PanelApp · NHS National Genomic Test Directory · ClinVar · UniProt · AlphaFold .