Gemini of Cajal bodies
Nuclear bodies frequently found near or associated with Cajal bodies (also called coiled bodies or CBs). Gemini of coiled bodies, or 'gems', are similar in size and shape to CBs, and often indistinguishable under the microscope. Unlike CBs, gems do not contain small nuclear ribonucleoproteins (snRNPs); they contain a protein called survivor of motor neurons (SMN) whose function relates to snRNP biogenesis. Gems are believed to assist CBs in snRNP biogenesis, and to play a role in the etiology of spinal muscular atrophy (SMA). [GO:0097504]
Synonyms: Gemini of coiled bodies; Gems
Part of: nuclear lumen (GO:0031981)
Components
| Component | Type | Part of / acts on | Grounding | Genes | Stoichiometry | Essential | Role |
|---|---|---|---|---|---|---|---|
| SMN protein | Protein | part of | Reviewed label only (reviewed name; no accession asserted) | UNKNOWN | Marker and resident protein concentrated in Gemini of Cajal bodies.
|
Taxonomic distribution
NCBITaxon:9606Homo sapiens — VARIABLE: Human HeLa cells were used to define gems as several SMN-containing nuclear foci frequently near or associated with coiled/Cajal bodies. [PMID:8670859]
Canonical examples
NCBITaxon:9606Homo sapiens — Liu and Dreyfuss localized SMN to two to six gem foci in HeLa nuclei and named them Gemini of coiled bodies because of their close association with coiled bodies. [PMID:8670859]
Functions
- snRNP biogenesis association — Gemini of Cajal bodies are SMN-containing nuclear bodies implicated in the same nuclear snRNP-biogenesis axis as Cajal bodies.
GO:0097504GO:0097504 states that gems contain SMN and are believed to assist Cajal bodies in snRNP biogenesis.DOI:10.1086/301992Matera and Frey 1998 reviewed gems and coiled bodies in the context of spinal muscular atrophy and small nuclear ribonucleoprotein biogenesis.
Mechanism graphs
SMN marks gems near Cajal bodies (FUNCTION)
Gemini of Cajal bodies are SMN-containing nuclear bodies that often sit near Cajal bodies and are associated with snRNP biogenesis.
| Subject | Predicate | Object | Evidence |
|---|---|---|---|
| SMN protein | localizes to | Gemini of Cajal bodies |
|
| Gemini of Cajal bodies | are associated with | Cajal body |
|
| Gemini of Cajal bodies | associated with | snRNP biogenesis association |
|
Discussions
- CURATION_TODO (OPEN): Resolve exact SMN paralog, Gemin subunit, SMN-complex and Cajal-body boundary claims for Gemini of Cajal bodies. This first GO:0097504 record captures the GO term, SMN localization and gem/Cajal-body adjacency while leaving SMN1-versus-SMN2, Gemin protein, full SMN-complex, and gem-versus-Cajal-body identity boundaries to a later pass.
Evidence
GO:0097504Gene Ontology cellular-component term for Gemini of Cajal bodies and the exact Gems and Gemini of coiled bodies synonyms.GO:0016604Gene Ontology cellular-component parent term for nuclear body.GO:0031981Gene Ontology cellular-component term for the nuclear lumen; gems are nuclear bodies.PMID:8670859Liu and Dreyfuss 1996, A novel nuclear structure containing the survival of motor neurons protein, EMBO Journal.DOI:10.1086/301992Matera and Frey 1998, Coiled bodies and gems: Janus or gemini?, American Journal of Human Genetics.DOI:10.1146/annurev.cellbio.16.1.273Gall 2000, Cajal bodies: the first 100 years, Annual Review of Cell and Developmental Biology.
Curation history
2026-09-28T08:10:23Zcodex · CREATED_RECORD — Scaffolded by scripts/new_record.py2026-09-28T08:11:41Zcodex · EXPANDED_RECORD — Added GO gem synonymy, nuclear-body parentage, nuclear-lumen parthood, an SMN label-only component, human HeLa scope, snRNP-biogenesis association evidence, a nonmechanistic SMN/gems graph, and an SMN-complex/Cajal-body boundary TODO.