Hypertrophic cardiomyopathy (HCM) is the most common inherited heart disease, affecting roughly 1 in 500 people, yet for decades its molecular origins remained frustratingly abstract — clinicians knew which genes mutated, but not precisely how those mutations disrupted the physical machinery of contraction. A high-resolution structural map of the cardiac thick filament may now change that calculus entirely.
Published in PNAS, this structural biology study resolves the native cardiac thick filament — the core contractile assembly built from myosin, titin, myosin-binding protein C, and associated regulatory proteins — at near-atomic detail. By capturing the filament in its physiological, macromolecular context rather than as isolated protein fragments, the researchers identified specific protein–protein interfaces where HCM-linked mutations cluster. These pathogenic interfaces appear to govern the transition between the filament's "off" (super-relaxed) and "on" (force-generating) states, a regulatory toggle that, when disrupted, is thought to produce the hypercontractility and pathological hypertrophy characteristic of HCM.
This finding is potentially paradigm-shifting for drug development. Most existing HCM therapies — including the recently approved myosin inhibitors mavacamten and aficamten — were developed with incomplete structural knowledge of their target. Knowing the precise geometry of pathogenic interfaces opens a rational design pathway for next-generation small molecules that could stabilize the filament's off-state with far greater selectivity. It also provides a structural framework for interpreting the roughly 1,500 known HCM-associated variants: mutations at or near identified interfaces would now carry stronger mechanistic weight as truly causative rather than merely correlated. Key limitations to acknowledge: structural snapshots do not capture filament dynamics under physiological loading, and translation from structural insight to clinical therapy involves substantial additional steps. Nevertheless, as a foundation for structure-guided medicine in inherited cardiomyopathy, this work represents a meaningful advance.