MYH6 (Alpha-Myosin Heavy Chain)
Details
MYH6 encodes the α-myosin heavy chain, a myosin isoform expressed predominantly in the adult human atrium (in contrast to MYH7/β-myosin, which predominates in the ventricle). Its atrial-predominant expression makes MYH6 of particular interest in atrial arrhythmias. Rare variants in MYH6 have been associated with sick sinus syndrome, dilated cardiomyopathy, and early-onset atrial fibrillation.
Key Facts
- Atrial expression: MYH6 is the dominant myosin heavy chain isoform in adult human atrium; its dysfunction may therefore selectively impair atrial contractile function and promote atrial structural remodeling. This makes MYH6 variants a plausible cause of AF via an "atrial myopathy" mechanism. (sources/eoaf-jama-2021)
- Sick sinus syndrome: A rare MYH6 missense variant (p.Arg721Trp) was associated with high risk of sick sinus syndrome in a large Icelandic cohort (Holm 2011), establishing MYH6 as a cardiac disease gene beyond sarcomeric function.
- Early-onset AF: In 1293 patients with early-onset AF who underwent WGS, MYH6 was the third most prevalent gene with P/LP variants: 10 participants (7% of all disease-associated variants). Median age at AF diagnosis was 43 years (IQR 36–56). (sources/eoaf-jama-2021)
- Clinical implication: Together with MYH7, MYH6 findings support the importance of myosin heavy chain subunits in atrial structure and function. The atrial-predominant expression of MYH6 may explain why loss-of-function variants manifest primarily as AF rather than ventricular cardiomyopathy.
Contradictions / Open Questions
- Evidence base concentrated in founder populations — generalizability uncertain: The foundational association of MYH6-R721W with sick sinus syndrome derives from a large Icelandic cohort, which may reflect a founder effect. The early-onset AF findings (10 of 1293 patients) come from a predominantly white North American/European cohort. Whether MYH6 variants carry the same risk in diverse populations is unknown, limiting the generalizability of current evidence to global guideline application. (sources/eoaf-jama-2021)
- Mechanism of AF in MYH6 — atrial myopathy vs. direct arrhythmogenesis unresolved: MYH6's atrial-predominant expression supports an "atrial myopathy" model where structural remodeling drives AF. However, it is also plausible that myosin heavy chain dysfunction creates direct electrophysiological changes in atrial myocytes. The mechanism is clinically relevant: an atrial myopathy mechanism would predict AF recurrence post-cardioversion regardless of rhythm control strategy, while direct arrhythmogenesis might respond better to pharmacological suppression. (sources/eoaf-jama-2021)
- No management guidelines specific to MYH6-AF: Despite its identification as a disease-associated gene in early-onset AF, no guideline specifically addresses MYH6 variant management. Whether identified MYH6 P/LP variants should prompt cascade screening, ILR implantation, or prophylactic anticoagulation in pre-AF individuals is unstated — all management defaults to standard AF protocols without genotype modification. (sources/eoaf-jama-2021)
Connections
- Related to concepts/Early-Onset-Atrial-Fibrillation
- Related to concepts/Genetic-Testing-in-AF
- Related to entities/Atrial-Fibrillation
- Related to entities/MYH7