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DTNBP1
dystrobrevin binding protein 1
DTNBP1 is located on the short (p) arm of chromosome 6, at band 6p22.3. Arm ratio per GRCh38 - banding schematic.
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Overview
DTNBP1 (dystrobrevin binding protein 1) is located on chromosome 6 and encodes dysbindin-1, a 351-amino-acid protein involved in regulating intracellular membrane trafficking. The gene was originally identified through its interaction with dystrobrevin, a component of the dystrophin-associated protein complex in muscle. Dysbindin-1 functions as part of the biogenesis of lysosome-related organelles complex-1 (BLOC-1), which is essential for the proper formation of specialised cellular compartments. Pathogenic variants in DTNBP1 are inherited in an autosomal recessive pattern, meaning both gene copies must carry variants for clinical manifestations to occur. The protein is particularly critical in haematopoietic cells, where it influences platelet formation and function.
What the gene does
Dysbindin-1 serves as a core component of BLOC-1, an eight-subunit protein complex that regulates the trafficking of cargo proteins to lysosome-related organelles. These specialised compartments include melanosomes in pigment cells, dense granules in platelets, and synaptic vesicles in neurons. Within BLOC-1, dysbindin-1 helps coordinate the sorting and delivery of membrane proteins from early endosomes to their final destinations. The protein achieves this by interacting with other trafficking machinery components, including adaptor protein complexes and small GTPases that direct vesicle movement along the cytoskeleton. In megakaryocytes, the bone marrow cells that produce platelets, dysbindin-1 is essential for assembling dense granules, which store molecules such as adenosine diphosphate and serotonin required for proper clotting responses. Loss of functional dysbindin-1 disrupts this trafficking pathway, leading to defects in organelle formation and impaired cellular function across multiple tissue types.
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Chromosome location
DTNBP1 is located on the short arm of chromosome 6 at position 22.3 (6p22.3). The gene spans approximately 140 kilobases of genomic DNA and contains multiple exons that are transcribed and spliced to produce the mature messenger RNA. The chromosomal region 6p22 contains several other genes involved in immune function and cellular signalling, though DTNBP1 itself is not part of a functionally related gene cluster.
Protein structure
The dysbindin-1 protein comprises 351 amino acids organised into several functional regions. A coiled-coil domain extends from amino acids 88 to 181, facilitating protein-protein interactions with other BLOC-1 subunits and trafficking machinery components. The dysbindin region spans amino acids 173 to 331 and represents the core functional domain responsible for the protein's role in vesicle formation. A nuclear export signal motif is present at amino acids 243 to 256, though dysbindin-1 primarily functions in the cytoplasm. The C-terminal portion of the protein, from amino acids 286 to 351, is predicted to be disordered, lacking fixed three-dimensional structure and potentially providing flexibility for regulatory interactions.
Key variants
Pathogenic variants in DTNBP1 are distributed across the coding sequence and include missense changes, nonsense mutations, and small insertions or deletions that disrupt protein function. Many disease-causing variants affect the dysbindin core region or the coiled-coil domain, impairing the protein's ability to assemble into functional BLOC-1 complexes. The carrier frequency for DTNBP1 variants varies among populations, with certain pathogenic changes identified more commonly in specific ethnic groups. Autosomal recessive inheritance means carriers with one variant copy typically remain asymptomatic, whilst individuals with variants in both gene copies may develop clinical features.
Sample of pathogenic variants
9 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.307C>T | p.Gln103Ter | Pathogenic | ★★☆☆ | Hermansky-Pudlak syndrome 7 |
c.448_449del | p.Met150fs | Pathogenic/Likely pathogenic | ★★☆☆ | Hermansky-Pudlak syndrome |
c.664C>T | p.Arg222Ter | Pathogenic/Likely pathogenic | ★★☆☆ | DTNBP1-related disorder |
c.79_83del | p.Ser27fs | Pathogenic/Likely pathogenic | ★★☆☆ | Hermansky-Pudlak syndrome 7 |
g.(?_15637955)_(15638055_?)del | - | Pathogenic | ★☆☆☆ | not provided |
g.15593076TCCT[1] | - | Pathogenic | ★☆☆☆ | not provided |
c.164del | p.Tyr55fs | Pathogenic | ★☆☆☆ | not provided |
c.93del | p.Lys31_Val32insTer | Pathogenic | ★☆☆☆ | not provided |
c.177G>A | p.Trp59Ter | Pathogenic | - | Hermansky-Pudlak syndrome 7 |
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
Biallelic pathogenic variants in DTNBP1 have been associated with bleeding disorders characterised by platelet dysfunction. Affected individuals may present with prolonged bleeding times, easy bruising, and excessive bleeding following injury or surgical procedures due to defective platelet dense granule formation. The severity of bleeding manifestations can vary depending on the specific variants involved and residual dysbindin-1 function. Some research has also explored potential associations between DTNBP1 variants and neuropsychiatric conditions, though these connections remain less clearly established than the haematological phenotypes.
No disease links recorded for this gene in our reference set.
Inheritance pattern
Conditions caused by pathogenic DTNBP1 variants typically follow autosomal recessive inheritance.
When both parents are carriers, each child has a 25% chance of being affected, 50% of being a carrier, and 25% of being unaffected.
UK clinical status
DTNBP1 is included on several NHS Genomic Medicine Service gene panels used for diagnosing inherited conditions. The gene appears on the Bleeding and platelet disorders panel with green classification (version R90), indicating strong evidence supporting its role in these conditions. It is also listed on the Inherited bleeding disorders panel with green classification, reflecting confidence in the gene-disease relationship for clinical diagnostic use within the NHS framework.
Sources: NHS GMS PanelApp · Genomics England PanelApp · NHS National Genomic Test Directory
Frequently asked questions
What does it mean to be a carrier of a DTNBP1 variant?
Being a carrier means you have one pathogenic variant in DTNBP1 whilst your other gene copy functions normally. Carriers typically do not develop symptoms because one working copy is sufficient for normal protein function. However, carriers can pass the variant to their children.
How is DTNBP1 inherited?
DTNBP1-related conditions follow an autosomal recessive inheritance pattern. This means a child must inherit pathogenic variants in both gene copies (one from each parent) to be affected. If both parents are carriers, each pregnancy has a 25% chance of the child being affected, a 50% chance of being a carrier, and a 25% chance of inheriting two working copies.
Why is DTNBP1 important for platelet function?
DTNBP1 encodes dysbindin-1, which helps form dense granules inside platelets. These granules store molecules needed for blood clotting. When dysbindin-1 is absent or non-functional, platelets cannot form proper dense granules, leading to impaired clotting ability and increased bleeding tendency.