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KPTN
kaptin, actin binding protein
KPTN is located on the long (q) arm of chromosome 19, at band 19q13.32. Arm ratio per GRCh38 - banding schematic.
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Overview
KPTN encodes kaptin, an actin-binding protein predominantly expressed in the brain during development and in mature neural tissue. This gene is located on chromosome 19 and produces a 436-amino-acid protein essential for proper neurological function. Pathogenic changes in KPTN have been linked to neurodevelopmental conditions affecting cognitive ability and seizure control.
The protein participates in cellular processes involving the actin cytoskeleton, which provides structural support and enables cell movement and division. Research suggests that disruption of kaptin function particularly affects neurons, where precise control of cell shape and connectivity is fundamental to brain development and ongoing neural activity.
What the gene does
Kaptin functions as an actin-binding protein, interacting with actin filaments that form part of the cell's structural framework. The cytoskeleton regulates cell shape, movement, and internal organisation, processes especially important in developing and mature neurons. Evidence suggests that kaptin influences how cells respond to signals that control growth and differentiation.
Within neural cells, kaptin appears to coordinate aspects of cytoskeletal dynamics required for proper neuronal migration during brain development and for maintaining neuronal architecture in adulthood. The protein's actin-binding activity may regulate how neurons extend processes, form connections, and respond to developmental cues. When kaptin function is impaired, these cellular processes can be disrupted, potentially affecting brain structure and electrical activity patterns that underlie normal cognitive function and seizure threshold.
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Chromosome location
KPTN is located on the long arm of chromosome 19 at position 19q13.32. This chromosomal region contains numerous genes, and the specific band 19q13.32 has been associated with several inherited conditions. The gene spans multiple exons that are transcribed and processed to produce the mature messenger RNA template for kaptin protein synthesis.
Protein structure
Domain architecture has not been experimentally characterised in detail for this protein. Kaptin contains 436 amino acids and possesses regions capable of binding actin filaments, though the precise structural organisation of functional domains remains an area of ongoing research. Structural studies may help clarify how specific portions of the protein mediate its interaction with the actin cytoskeleton and other cellular components.
Key variants
Pathogenic variants in KPTN typically result in loss of normal protein function. These changes may include deletions, insertions, or single-nucleotide substitutions that alter the protein's ability to bind actin or participate in cytoskeletal regulation. The clinical impact of KPTN variants depends on how severely they disrupt kaptin activity, with complete loss of function generally associated with more pronounced neurological features.
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.184dup | p.Ile62fs | Pathogenic/Likely pathogenic | ★★☆☆ | See cases |
c.597_598dup | p.Ser200fs | Pathogenic/Likely pathogenic | ★★☆☆ | Macrocephaly-developmental delay syndrome |
c.714_731dup | p.Gln246_Asp247insMetTrpSerValLeuGln | Pathogenic/Likely pathogenic | ★★☆☆ | Inborn genetic diseases |
c.776C>A | p.Ser259Ter | Pathogenic | ★★☆☆ | Inborn genetic diseases |
c.777_783dup | p.Lys262fs | Pathogenic | ★★☆☆ | Macrocephaly-developmental delay syndrome |
c.397_398delAG | - | Pathogenic | ★☆☆☆ | Macrocephaly-developmental delay syndrome |
c.391del | p.Ala131fs | Pathogenic | ★☆☆☆ | Macrocephaly-developmental delay syndrome |
c.394+1G>T | - | Pathogenic | ★☆☆☆ | Macrocephaly-developmental delay syndrome |
c.599+1G>T | - | Pathogenic | ★☆☆☆ | Macrocephaly-developmental delay syndrome |
c.644_653dup | p.Leu219fs | Pathogenic | ★☆☆☆ | Macrocephaly-developmental delay syndrome |
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 KPTN are primarily associated with neurodevelopmental disorders characterised by intellectual disability and epilepsy. Affected individuals typically present in early childhood with developmental delays, learning difficulties, and seizures that may be difficult to control with standard treatments. The spectrum of clinical features can vary among individuals, but cognitive impairment and early-onset seizures represent core manifestations. Some affected individuals may also exhibit additional features such as behavioural differences or motor coordination challenges, reflecting the protein's importance in multiple aspects of brain development and function.
No disease links recorded for this gene in our reference set.
UK clinical status
KPTN appears on several NHS Genomic Medicine Service gene panels that guide clinical genetic testing for specific conditions. The gene is listed on the Intellectual Disability panel (R29) and the Early Onset or Syndromic Epilepsy panel (R59), both with green classification indicating sufficient evidence for clinical use. KPTN is also included in the Developmental Disorders Genotype-to-Phenotype (DDG2P) database with green status, reflecting established evidence linking variants in this gene to developmental conditions. These panel memberships support the use of KPTN testing when evaluating patients with unexplained intellectual disability or early seizure disorders within the NHS.
Sources: NHS GMS PanelApp · Genomics England PanelApp · NHS National Genomic Test Directory
Frequently asked questions
What does the KPTN gene do?
KPTN provides instructions for making kaptin, a protein that binds to actin filaments within cells. This interaction helps regulate the cell's structural framework, particularly important in developing and mature neurons where precise control of cell shape and connectivity is essential for normal brain function.
What conditions are associated with KPTN variants?
Pathogenic variants in KPTN are linked to neurodevelopmental disorders characterised by intellectual disability and early-onset epilepsy. Affected individuals typically experience developmental delays, learning difficulties, and seizures beginning in childhood.
Is KPTN testing available on the NHS?
Yes, KPTN is included on NHS Genomic Medicine Service panels for intellectual disability and early-onset or syndromic epilepsy. Testing may be offered through the NHS when a patient's clinical presentation suggests a genetic cause for these conditions.