C21orf2 — Chromosome 21 Open Reading Frame 2

C21orf2 — Chromosome 21 Open Reading Frame 2

Overview

C21orf2 — Chromosome 21 Open Reading Frame 2

Overview

<table class="infobox infobox-gene">
<tr>
<th class="infobox-header" colspan="2">C21orf2 — Chromosome 21 Open Reading Frame 2</th>
</tr>
<tr>
<td class="label">Symbol</td>
<td><strong>C21ORF2</strong></td>
</tr>
<tr>
<td class="label">Full Name</td>
<td>C21orf2 — Chromosome 21 Open Reading Frame 2</td>
</tr>
<tr>
<td class="label">Type</td>
<td>Gene</td>
</tr>
<tr>
<td class="label">NCBI</td>
<td><a href="https://www.ncbi.nlm.nih.gov/gene/?term=C21ORF2" target="_blank">Search NCBI</a></td>
</tr>
<tr>
<td class="label">Associated Diseases</td>
<td><a href="/wiki/als" style="color:#ef9a9a">Als</a>, <a href="/wiki/amyotrophic-lateral-sclerosis" style="color:#ef9a9a">Amyotrophic Lateral Sclerosis</a>, <a href="/wiki/ms" style="color:#ef9a9a">Ms</a></td>
</tr>
<tr>
<td class="label">KG Connections</td>
<td><a href="/atlas" style="color:#4fc3f7">28 edges</a></td>
</tr>
</table>

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](/entities/neurons).[@wheway2015][@van2016] In neurodegeneration contexts, C21orf2 is often discussed with [NEK1](/genes/nek1), because both proteins localize to ciliary/centrosomal compartments and variants in both genes appear in ALS cohorts.[@van2016][@kenna2016]

The encoded protein (C21orf2 protein) is represented at [C21orf2 Protein](/proteins/c21orf2-protein). Clinical and mechanistic links are strongest for [ALS](/diseases/amyotrophic-lateral-sclerosis), with additional relevance to ciliopathy phenotypes that can modify neurodevelopmental and neurodegenerative vulnerability.[@wheway2015][@khan2015]

Function

C21orf2 participates in centrosome and basal-body biology, helping coordinate ciliary assembly and organization.[@wheway2015][@reiter2017] 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.[@reiter2017][@liuyesucevitz2011]

Multiple studies indicate that ALS-associated C21orf2 variants reduce normal protein function and perturb interactions with ciliary partners, including NEK1-linked networks.[@van2016][@kenna2016] This creates a plausible mechanistic bridge between genetic susceptibility and downstream motor-neuron degeneration through altered trafficking, organelle stress, and impaired quality-control pathways.[@kenna2016][@liuyesucevitz2011]

Disease Associations

Amyotrophic Lateral Sclerosis

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.[@van2016][@kenna2016] 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.[@van2016][@kenna2016]

Ciliopathy-Related Syndromes

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.[@wheway2015][@khan2015] These syndromic observations strengthen the biological plausibility of C21orf2-mediated cellular dysfunction in CNS tissue.

Brain Expression and Cellular Context

Public transcriptomic resources show broad but generally low-to-moderate C21orf2 expression across CNS regions, with detectable expression in neuronal and glial compartments.[@gtex2020] Given its localization and partner network, C21orf2 is best interpreted as a cellular homeostasis gene influencing stress tolerance rather than a classic neurotransmission effector.

Clinical and Research Implications

• In ALS genetics panels, C21orf2 can be included alongside [TBK1](/genes/tbk1), [OPTN](/genes/optn), [TARDBP](/genes/tardbp), and [FUS](/entities/fus) for expanded risk profiling.
• Variant interpretation should use ACMG/AMP criteria and disease-specific curation frameworks due to uncertain penetrance for many missense changes.[@richards2015]
• Priority experiments include CRISPR isogenic motor-neuron models to quantify how C21orf2 variant classes alter ciliogenesis, axonal transport, and stress granule dynamics.

See Also

• [C21orf2 Protein](/proteins/c21orf2-protein)
• [NEK1](/genes/nek1)
• [Amyotrophic Lateral Sclerosis](/diseases/amyotrophic-lateral-sclerosis)
• [Axonal Transport Dysfunction](/mechanisms/axonal-transport-defects)

External Links

• [NCBI Gene: c21orf2](https://www.ncbi.nlm.nih.gov/gene/)
• [PubMed: c21orf2](https://pubmed.ncbi.nlm.nih.gov/?term=c21orf2+neurodegeneration)

References

Pathway Diagram

The following diagram shows the key molecular relationships involving C21orf2 — Chromosome 21 Open Reading Frame 2 discovered through SciDEX knowledge graph analysis: