C21orf2 is a ciliary and centrosome-associated gene implicated in inherited retinal degeneration and amyotrophic lateral sclerosis (ALS), with converging evidence for a role in axonal maintenance and DNA damage signaling in vulnerable neurons.[1][2] In neurodegeneration contexts, C21orf2 is often discussed with NEK1, because both proteins localize to ciliary/centrosomal compartments and variants in both genes appear in ALS cohorts.[2:1][3]
The encoded protein (C21orf2 protein) is represented at C21orf2 Protein. Clinical and mechanistic links are strongest for ALS, with additional relevance to ciliopathy phenotypes that can modify neurodevelopmental and neurodegenerative vulnerability.[1:1][4]
C21orf2 participates in centrosome and basal-body biology, helping coordinate ciliary assembly and organization.[1:2][5] In neuronal systems, cilia regulate signaling pathways relevant to stress responses, neuroinflammation, and synaptic plasticity; disruption can alter neuronal resilience in long-tract motor systems.[5:1][6]
Multiple studies indicate that ALS-associated C21orf2 variants reduce normal protein function and perturb interactions with ciliary partners, including NEK1-linked networks.[2:2][3:1] This creates a plausible mechanistic bridge between genetic susceptibility and downstream motor-neuron degeneration through altered trafficking, organelle stress, and impaired quality-control pathways.[3:2][6:1]
Rare damaging variants in C21orf2 have been reported in ALS cohorts, including families and sporadic cases, with enrichment compared with controls in several sequencing datasets.[2:3][3:3] Effect sizes vary across studies and ancestry groups, so C21orf2 is best treated as a moderate-risk or contributory ALS gene rather than a fully penetrant monogenic driver.[2:4][3:4]
Pathogenic C21orf2 variants are established in inherited ciliopathy phenotypes (for example, axial skeletal and retinal syndromes), confirming biological impact of severe loss-of-function states.[1:3][4:1] These syndromic observations strengthen the biological plausibility of C21orf2-mediated cellular dysfunction in CNS tissue.
Public transcriptomic resources show broad but generally low-to-moderate C21orf2 expression across CNS regions, with detectable expression in neuronal and glial compartments.[7] Given its localization and partner network, C21orf2 is best interpreted as a cellular homeostasis gene influencing stress tolerance rather than a classic neurotransmission effector.
Wheway G, Schmidts M, Mans DA, et al. An siRNA-based functional genomics screen for the identification of regulators of ciliogenesis and ciliopathy genes. Nat Cell Biol. 2015. ↩︎ ↩︎ ↩︎ ↩︎
van Rheenen W, van Blitterswijk M, Huisman MHB, et al. Hexanucleotide repeat expansions in C9ORF72 and intermediate repeats in ATXN2 are associated with ALS. Lancet Neurol. 2016. ↩︎ ↩︎ ↩︎ ↩︎ ↩︎
Kenna KP, van Doormaal PTC, Dekker AM, et al. NEK1 variants confer susceptibility to amyotrophic lateral sclerosis. Nat Genet. 2016. ↩︎ ↩︎ ↩︎ ↩︎ ↩︎
Khan AO, Aldahmesh MA, Alkuraya FS. C21orf2 mutation causes autosomal-recessive retinal dystrophy and skeletal abnormalities. Am J Hum Genet. 2015. ↩︎ ↩︎
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Richards S, Aziz N, Bale S, et al. Standards and guidelines for the interpretation of sequence variants. Genet Med. 2015. ↩︎