THOC2: A Key Component of the THO Complex in mRNA Export and Neurodevelopment
Comprehensive genomic and clinical overview of THOC2, a gene linked to X-linked intellectual disability and mRNA processing
Gene Information Card
| Symbol | THOC2 |
|---|---|
| Full Name | THO complex 2 |
| Gene Type | Protein coding |
| Chromosomal Location | Xq25 |
| NCBI Gene ID | 57187 ncbi.nlm.nih.gov/gene/57187 |
| Ensembl ID | ENSG00000125676 |
| UniProt ID | Q8NI27 |
| OMIM ID | 300395 |
| HGNC ID | 19073 |
| Aliases | CXorf3, THO2, hTREX120 |
Description
THOC2 encodes a core component of the THO complex, which is part of the TREX (transcription/export) complex. This complex is essential for efficient mRNA export from the nucleus to the cytoplasm, coupling transcription to mRNA processing and export. THOC2 is ubiquitously expressed and plays a critical role in cellular mRNA metabolism. Mutations in THOC2 cause X-linked intellectual disability (XLID) with variable neurological features, including developmental delay, speech impairment, and behavioral abnormalities.
Disease Associations
| Disease category | Pathophysiological mechanism | Genomic evidence |
|---|---|---|
| X-linked intellectual disability (XLID) with THOC2 variants | Loss-of-function or missense mutations in THOC2 impair THO/TREX complex assembly and mRNA export, leading to defective neuronal gene expression and synaptic function. | ClinVar, OMIM #300395 |
| THOC2-related neurodevelopmental disorder | Dominant-negative or hypomorphic alleles disrupt mRNA export in developing neurons, causing global developmental delay, hypotonia, and seizures. | ClinVar, PubMed studies |
Expression Profile
Tissue Expression
| Tissue | nTPM | level |
|---|---|---|
| Brain (cerebral cortex) | 12.5 | Medium |
| Testis | 15.3 | Medium |
| Lymph node | 10.1 | Medium |
| Liver | 8.7 | Low |
| Heart | 9.2 | Low |
Cell Line Expression
| Cell Line | nTPM | Notes |
|---|---|---|
| HEK293 | 14.0 | Embryonic kidney, high expression |
| HeLa | 11.5 | Cervical carcinoma, moderate |
| SH-SY5Y | 13.2 | Neuroblastoma, relevant for neuronal studies |
| K562 | 9.8 | Leukemia, moderate |
Data source：Human Protein Atlas（proteinatlas.org）
Mutations & Variants
Hotspot Mutations
| Variant | Type | Frequency | Functional Description |
|---|---|---|---|
| c.1280A>G (p.Asn427Ser) | Missense | Rare | Impaired THO complex assembly, reduced mRNA export |
| c.2263C>T (p.Arg755Trp) | Missense | Rare | Dominant-negative effect, associated with XLID |
| c.3445C>T (p.Arg1149*) | Nonsense | Very rare | Loss-of-function, predicted nonsense-mediated decay |
Mutation functional classification
Loss of Function (LOF)
Nonsense and frameshift mutations leading to truncated protein or mRNA decay, resulting in haploinsufficiency.
Gain of Function (GOF)
Not reported for THOC2; no activating mutations known.
Dominant Negative (DN)
Missense mutations (e.g., p.Arg755Trp) that disrupt THO complex integrity and inhibit wild-type function.
View complete mutation data：
Gene Ontology (GO)
| • mRNA export from nucleus (GO:0006406) | • transcription-coupled nucleotide-excision repair (GO:0006283) |
| • THO complex (GO:0000347) | • nucleus (GO:0005634) |
| • protein binding (GO:0005515) |
Pathways
• mRNA export (TREX complex pathway)
• Transcription-coupled repair (TCR)
Protein Summary
THOC2 is a 1593-amino acid protein (UniProt Q8NI27) that forms the scaffold of the THO subcomplex within TREX. It interacts with THOC1, THOC3, and other TREX components to facilitate the loading of export factors onto mRNA. The protein contains multiple coiled-coil domains and is predominantly nuclear. Structural studies indicate that THOC2 is essential for the stability of the entire THO complex.
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