MYL4: Myosin Light Chain 4 – Atrial-Specific Cardiac Muscle Protein
Essential regulator of atrial contractility and sarcomere assembly; mutations linked to atrial cardiomyopathy and arrhythmia
Gene Information Card
| Symbol | MYL4 |
|---|---|
| Full Name | Myosin Light Chain 4 |
| Gene Type | protein-coding |
| Chromosomal Location | 17q21.32 |
| NCBI Gene ID | 4635 ncbi.nlm.nih.gov/gene/4635 |
| Ensembl ID | ENSG00000108349 |
| UniProt ID | P12829 |
| OMIM ID | 160770 |
| HGNC ID | 7584 |
| Aliases | ALC1, MLC1, MLC-1, MLC1v, MYL4A |
Description
MYL4 encodes the atrial isoform of myosin light chain 1 (MLC1), a component of the hexameric myosin complex in cardiac muscle. It is predominantly expressed in the atria and plays a critical role in regulating actin-myosin interaction and sarcomere contraction. Mutations in MYL4 are associated with atrial cardiomyopathy, atrial fibrillation, and early-onset atrial arrhythmias.
Disease Associations
| Disease category | Pathophysiological mechanism | Genomic evidence |
|---|---|---|
| Atrial cardiomyopathy with arrhythmia | Disrupted sarcomere assembly due to MYL4 missense or truncating variants leads to impaired atrial contractility and electrical instability | ClinVar, OMIM |
| Atrial fibrillation | MYL4 mutations alter myosin light chain function, increasing susceptibility to atrial fibrillation through structural and electrical remodeling | ClinVar, PubMed |
| Dilated cardiomyopathy (atrial-predominant) | Loss of MYL4 function reduces atrial myosin stability, causing progressive atrial dilation and systolic dysfunction | OMIM, NCBI |
Expression Profile
Tissue Expression
| Tissue | nTPM | level |
|---|---|---|
| Heart (atrial appendage) | 58.2 | High |
| Heart (left ventricle) | 12.1 | Medium |
| Skeletal muscle | 3.5 | Low |
| Esophagus | 1.2 | Low |
| Thyroid | 0.8 | Not detected |
Cell Line Expression
| Cell Line | nTPM | Notes |
|---|---|---|
| AC16 (cardiomyocyte) | 45.6 | Atrial-like expression |
| HL-1 (atrial myocyte) | 62.3 | High endogenous expression |
| H9c2 (rat cardiomyoblast) | 8.9 | Low expression |
Data source：Human Protein Atlas（proteinatlas.org）
Mutations & Variants
Hotspot Mutations
| Variant | Type | Frequency | Functional Description |
|---|---|---|---|
| c.64G>A (p.Glu22Lys) | Missense | <0.01% | Alters actin-binding affinity; associated with atrial fibrillation |
| c.173C>T (p.Pro58Leu) | Missense | <0.01% | Disrupts myosin light chain folding; linked to atrial cardiomyopathy |
| c.430C>T (p.Arg144*) | Nonsense | <0.01% | Premature truncation; loss of function; severe atrial arrhythmia |
Mutation functional classification
Loss of Function (LOF)
Nonsense and frameshift variants (e.g., p.Arg144*) cause haploinsufficiency, reducing atrial myosin light chain levels and impairing sarcomere integrity.
Gain of Function (GOF)
Not reported for MYL4; no activating mutations have been described.
Dominant Negative (DN)
Missense mutations (e.g., p.Glu22Lys) produce a defective protein that interferes with wild-type myosin assembly, leading to dominant-negative effects on atrial contractility.
View complete mutation data：
Gene Ontology (GO)
| • actin binding (GO:0003779) | • ATP binding (GO:0005524) |
| • structural constituent of muscle (GO:0008307) | • muscle filament sliding (GO:0030049) |
| • cardiac muscle contraction (GO:0060048) |
Pathways
• Cardiac muscle contraction (KEGG: hsa04260)
• Hypertrophic cardiomyopathy (KEGG: hsa05410)
• Dilated cardiomyopathy (KEGG: hsa05414)
Protein Summary
MYL4 encodes the atrial-specific myosin light chain 1 (MLC1), a 22 kDa protein that binds to the myosin heavy chain head and modulates actin-activated ATPase activity. It is essential for proper atrial sarcomere function. The protein contains three EF-hand domains that coordinate calcium binding and stabilize the myosin lever arm. Mutations in MYL4 disrupt calcium sensitivity and force generation, leading to atrial myopathy.
Related Services
Related Products
| Product name | Cat.No. | Species | Gene ID | |
|---|---|---|---|---|
| MYL4 Knockout HEK293 Cell Line | EDJ-KQ1440 | Human | 4635 | Details Get a Quote |
| MYL4 Knockout HeLa Cell Line | EDJ-KQ53948 | Human | 4635 | Details Get a Quote |
| MYL4 Knockout A-549 Cell Line | EDJ-KQ62441 | Human | 4635 | Details Get a Quote |
| MYL4 Knockout HCT 116 Cell Line | EDJ-KQ70906 | Human | 4635 | Details Get a Quote |
