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CCDC103
dynein axonemal assembly factor 19
CCDC103 is located on the long (q) arm of chromosome 17, at band 17q21.31. Arm ratio per GRCh38 - banding schematic.
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Clinical tests that include this
Overview
CCDC103 provides instructions for producing dynein axonemal assembly factor 19, a protein critical for constructing the machinery that powers ciliary movement. Cilia are microscopic, finger-like projections on cell surfaces that beat in coordinated waves to move fluid and mucus. In the respiratory tract, cilia sweep mucus and trapped particles out of the airways. During embryonic development, cilia also establish the left-right body axis. When CCDC103 function is lost, cilia either fail to form properly or cannot beat effectively, resulting in a spectrum of clinical features collectively termed primary ciliary dyskinesia. This condition follows an autosomal recessive inheritance pattern, meaning both gene copies must carry pathogenic variants for disease to manifest.
What the gene does
The CCDC103 protein acts as an assembly factor for outer dynein arms, multi-subunit molecular motors that attach to the microtubule doublets forming the ciliary skeleton. Dynein arms generate the sliding forces between microtubules that bend the cilium, creating the characteristic back-and-forth beating motion. CCDC103 specifically facilitates the proper folding, transport, and attachment of heavy-chain dynein components to the ciliary axoneme. Without functional CCDC103, outer dynein arms either do not assemble onto the axoneme or are structurally defective, leading to immotile or dyskinetic cilia. The protein is thought to work in concert with other assembly factors in the cytoplasm before dynein complexes are transported into the cilium. Loss of CCDC103 therefore disrupts both the structural integrity and motility of cilia across multiple organ systems, from the respiratory epithelium to the fallopian tubes and sperm flagella.
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Chromosome location
CCDC103 is located on chromosome 17 at position 17q21.31. This chromosomal region contains several genes associated with respiratory and developmental phenotypes. The genomic structure and precise exon count have not been extensively detailed in routine clinical references, though the locus encodes a relatively compact protein of 242 amino acids.
Protein structure
The CCDC103 protein spans 242 amino acids and contains a coiled-coil domain extending from amino acid 8 to 32. Coiled-coil motifs typically mediate protein-protein interactions, allowing CCDC103 to engage with other dynein assembly factors or dynein subunits during motor complex construction. Beyond this region, detailed experimental characterisation of additional functional domains remains limited in published structural databases.
Key variants
Pathogenic variants in CCDC103 are predominantly loss-of-function changes, including nonsense mutations, frameshift insertions or deletions, and splice-site alterations that abolish protein expression or truncate the product. Missense variants affecting the coiled-coil domain or other functionally constrained regions can also impair dynein assembly. Because primary ciliary dyskinesia is autosomal recessive, affected individuals typically carry biallelic pathogenic variants-either two copies of the same variant or compound heterozygous changes on each chromosome.
No pathogenic or likely-pathogenic ClinVar variants recorded yet for this gene.
Associated conditions
Biallelic pathogenic variants in CCDC103 cause primary ciliary dyskinesia, a disorder characterised by chronic respiratory infections, recurrent sinusitis, bronchiectasis, and situs abnormalities such as situs inversus totalis or heterotaxy. Many individuals experience neonatal respiratory distress and develop progressive lung disease over time. Male infertility due to immotile sperm and female subfertility from impaired fallopian tube ciliary function are also common. In some cases, ciliary dysfunction during embryogenesis leads to complex congenital heart defects or laterality disorders.
No disease links recorded for this gene in our reference set.
Inheritance pattern
Conditions caused by pathogenic CCDC103 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
CCDC103 is included on several NHS Genomic Medicine Service gene panels. It appears as a green gene on the DDG2P panel, the Primary ciliary disorders panel, the Respiratory ciliopathies including non-CF bronchiectasis panel (R189), the Fetal anomalies panel (R21), and the Laterality disorders and isomerism panel (R139). Green classification indicates strong evidence linking the gene to the associated conditions, supporting its use in diagnostic sequencing for individuals presenting with respiratory or laterality phenotypes.
Sources: NHS GMS PanelApp · Genomics England PanelApp · NHS National Genomic Test Directory
Frequently asked questions
What does CCDC103 stand for?
CCDC103 stands for coiled-coil domain containing 103. The gene is also known as dynein axonemal assembly factor 19, reflecting its role in assembling dynein motor complexes within cilia.
How is CCDC103-related primary ciliary dyskinesia inherited?
CCDC103-related primary ciliary dyskinesia follows an autosomal recessive inheritance pattern. An individual must inherit a pathogenic variant from both parents to develop the condition. Carriers with one variant copy typically remain unaffected.
Can CCDC103 variants affect fertility?
Yes, research suggests that biallelic CCDC103 variants can lead to infertility in both males and females. In males, sperm flagella rely on dynein motors for motility, and defective assembly results in immotile sperm. In females, ciliary dysfunction in the fallopian tubes may impair egg transport.