SMPX
Small Muscle Protein, X-linked
Gene Information Card
| Symbol | SMPX |
|---|---|
| Full Name | Small muscle protein, X-linked |
| Gene Type | Protein coding |
| Chromosomal Location | Xp22.12 |
| NCBI Gene ID | 23676 ncbi.nlm.nih.gov/gene/23676 |
| Ensembl ID | ENSG00000165219 |
| UniProt ID | Q9UQ90 |
| OMIM ID | 300226 |
| HGNC ID | 11168 |
| Aliases | DFNX4, Chisel, SMPX_HUMAN |
Description
The SMPX gene encodes a small, 88-amino acid protein that is highly expressed in skeletal and cardiac muscle. It is localized to the sarcomere and is thought to play a role in muscle mechanotransduction and maintenance of muscle structure. Mutations in SMPX cause X-linked non-syndromic hearing loss (DFNX4), likely due to dysfunction in the inner ear hair cells or supporting cells.
Disease Associations
| Disease category | Pathophysiological mechanism | Genomic evidence |
|---|---|---|
| X-linked non-syndromic hearing loss (DFNX4) | Loss-of-function mutations in SMPX lead to progressive sensorineural hearing loss, likely due to impaired mechanotransduction or structural integrity of cochlear hair cells. | ClinVar, OMIM |
| Hearing loss, X-linked 4 | Missense and nonsense variants in SMPX disrupt protein function, resulting in deafness. | NCBI Gene, OMIM |
Expression Profile
Tissue Expression
| Tissue | nTPM | level |
|---|---|---|
| Skeletal muscle | 24.5 | High |
| Heart | 18.2 | High |
| Testis | 1.2 | Low |
| Brain | 0.5 | Not detected |
Cell Line Expression
| Cell Line | nTPM | Notes |
|---|---|---|
| HeLa | 0.3 | Low expression |
| K562 | 0.1 | Not detected |
| HepG2 | 0.2 | Not detected |
Data source：Human Protein Atlas（proteinatlas.org）
Mutations & Variants
Hotspot Mutations
| Variant | Type | Frequency | Functional Description |
|---|---|---|---|
| c.2T>C (p.Met1Thr) | Missense | Rare | Loss of start codon, likely loss of function |
| c.106C>T (p.Arg36*) | Nonsense | Rare | Premature stop, loss of function |
| c.133G>A (p.Gly45Arg) | Missense | Rare | Impaired protein stability/function |
Mutation functional classification
Loss of Function (LOF)
Most SMPX mutations are loss-of-function (nonsense, frameshift, start-loss), leading to haploinsufficiency or truncated protein.
Gain of Function (GOF)
No gain-of-function mutations reported.
Dominant Negative (DN)
No dominant-negative mechanism described.
View complete mutation data：
Gene Ontology (GO)
| • protein binding (GO:0005515) | • striated muscle thin filament (GO:0005865) |
| • myofibril (GO:0030016) | • muscle contraction (GO:0006936) |
| • sensory perception of sound (GO:0007605) |
Pathways
• Striated muscle contraction (Reactome: R-HSA-390522)
• Muscle contraction (KEGG: hsa04260)
Protein Summary
The SMPX protein (UniProt Q9UQ90) is a small, 88-amino acid protein with a molecular weight of approximately 10 kDa. It is localized to the sarcomere in striated muscle and is also expressed in the cochlea. The protein contains a conserved domain of unknown function (DUF) and is involved in mechanotransduction. Loss of SMPX function leads to progressive hearing loss.
Related Services
Related Products
| Product name | Cat.No. | Species | Gene ID | |
|---|---|---|---|---|
| SMPX Knockout HEK293 Cell Line | EDJ-KQ8118 | Human | 23676 | Details Get a Quote |
| SMPX Knockout HeLa Cell Line | EDJ-KQ55793 | Human | 23676 | Details Get a Quote |
| SMPX Knockout A-549 Cell Line | EDJ-KQ64289 | Human | 23676 | Details Get a Quote |
| SMPX Knockout HCT 116 Cell Line | EDJ-KQ72737 | Human | 23676 | Details Get a Quote |
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