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DCX
doublecortin
The DCX gene provides instructions for producing the doublecortin protein, which is essential for normal neuronal migration and brain development. The DCX gene is vital for guiding nerve cells (neurons) to their correct positions in the developing brain, a process known as neuronal migration.
DCX is located on the long (q) arm of chromosome X, at band Xq23. Arm ratio per GRCh38 - banding schematic.
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Overview
The DCX gene, also known as doublecortin, plays a fundamental role in the development of the human brain. It encodes a protein that is crucial for neuronal migration, the process by which newly formed nerve cells move to their designated locations within the brain.
Disruptions in the function of the DCX gene can lead to significant developmental abnormalities of the brain, affecting its structure and function. Such abnormalities can manifest as neurological conditions with varying degrees of severity.
What the gene does
The DCX gene provides instructions for the doublecortin protein, which is actively involved in neuronal migration during brain development. This protein attaches to microtubules, which are structural components of cells forming part of the cytoskeleton. By binding to microtubules, doublecortin helps to stabilise these structures.
Microtubules are essential for the movement of neurons, as they form an internal scaffolding that elongates in a specific direction, altering the cell's internal framework and facilitating neuronal propulsion. The stabilising action of doublecortin on microtubules is therefore critical for the precise positioning of neurons, ensuring the brain develops its complex and organised structure.
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Chromosome location
The DCX gene is situated on the long arm of the X chromosome at position 23, designated as Xq23. This genomic location is significant because genes on the X chromosome follow specific inheritance patterns, which can influence how conditions associated with these genes are expressed in males and females.
Protein structure
The doublecortin protein, encoded by the DCX gene, is composed of 365 amino acids. Its structure includes several key regions essential for its function. There is a Disordered region spanning amino acids 11-31, followed by a Doublecortin 1 domain from amino acids 53-139. Another crucial region is the Doublecortin 2 domain, located between amino acids 180-263. The protein concludes with another Disordered region from amino acids 275-365. These domains and regions work together to facilitate the protein's interaction with microtubules and its role in neuronal migration.
Key variants
Genetic variations within the DCX gene can alter the function of the doublecortin protein. These variants include changes such as missense, nonsense, and frameshift mutations, as well as larger deletions or duplications. The specific impact of a variant often depends on its location within the gene and how it affects the protein's ability to bind to microtubules or perform its other essential functions in neuronal migration.
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.200G>A | p.Gly67Glu | Pathogenic/Likely pathogenic | ★★☆☆ | DCX-related disorder |
c.478del | p.Gln160fs | Pathogenic | ★★☆☆ | Lissencephaly type 1 due to doublecortin gene mutation |
c.478dup | p.Gln160fs | Pathogenic | ★★☆☆ | Lissencephaly type 1 due to doublecortin gene mutation |
c.505C>T | p.Gln169Ter | Pathogenic | ★★☆☆ | Lissencephaly type 1 due to doublecortin gene mutation |
c.536C>G | p.Pro179Arg | Pathogenic/Likely pathogenic | ★★☆☆ | Lissencephaly type 1 due to doublecortin gene mutation |
c.544G>T | p.Val182Phe | Pathogenic/Likely pathogenic | ★★☆☆ | Lissencephaly type 1 due to doublecortin gene mutation |
c.681dup | p.Leu228fs | Pathogenic | ★★☆☆ | Abnormal cortical gyration |
c.684_685del | p.Tyr229fs | Pathogenic | ★★☆☆ | Lissencephaly type 1 due to doublecortin gene mutation |
c.703C>T | p.Gln235Ter | Pathogenic | ★★☆☆ | not provided |
c.705+1G>A | - | Pathogenic | ★★☆☆ | not provided |
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 DCX gene are associated with conditions characterised by abnormal brain development. These conditions primarily affect neuronal migration, leading to structural anomalies of the brain. The severity and specific presentation can vary depending on the nature of the genetic change.
No disease links recorded for this gene in our reference set.
UK clinical status
The DCX gene is recognised in the UK National Health Service (NHS) Genomic Medicine Service. It is listed on several Green panels within PanelApp, including DDG2P, Early onset or syndromic epilepsy, Foetal anomalies (R21), Intellectual disability, and Malformations of cortical development, indicating its established role in these conditions for diagnostic testing.
Sources: NHS GMS PanelApp · Genomics England PanelApp · NHS National Genomic Test Directory
Frequently asked questions
What is the primary function of the DCX gene?
The DCX gene provides instructions for the doublecortin protein, which is crucial for neuronal migration, the process where nerve cells move to their correct positions during brain development.
How does the doublecortin protein work?
The doublecortin protein binds to microtubules, which are structural components within cells. By stabilising these microtubules, it helps nerve cells to move effectively to their proper locations in the developing brain.
What happens if there is a variant in the DCX gene?
Variants in the DCX gene can lead to abnormal brain development due to impaired neuronal migration. This can result in neurological conditions affecting brain structure and function.
References
- González-Morón D, Vishnopolska S, Consalvo D. Germline and somatic mutations in cortical malformations: Molecular defects in Argentinean patients with neuronal migration disorders. PloS one. 2017. PMID: 28953922
- Fry AE, Cushion TD, Pilz DT. The genetics of lissencephaly. American journal of medical genetics. Part C, Seminars in medical genetics. 2014. PMID: 24862549
- Bahi-Buisson N, Souville I, Fourniol FJ. New insights into genotype-phenotype correlations for the doublecortin-related lissencephaly spectrum. Brain : a journal of neurology. 2013. PMID: 23365099
- Friocourt G, Marcorelles P, Saugier-Veber P. Role of cytoskeletal abnormalities in the neuropathology and pathophysiology of type I lissencephaly. Acta neuropathologica. 2011. PMID: 21046408
- Liu JS. Molecular genetics of neuronal migration disorders. Current neurology and neuroscience reports. 2011. PMID: 21222180