Coupled Instability and Probabilistic Control in TDP-43 Pathology

Amyotrophic lateral sclerosis (ALS) is commonly described as the cumulative outcome of discrete molecular defects in TDP-43 homeostasis, including nuclear transport failure, cytoplasmic mislocalization, stress granule persistence, proteolytic fragmentation, and RNA dysregulation. However, these processes are typically studied in isolation, limiting the ability to explain the heterogeneous and non-linear nature of disease onset and progression. Here, we propose a multi-axis instability framework from a systems biology perspective in which TDP-43 pathology is conceptualized as a coupled dynamical system evolving within a multi-dimensional state space. In this formulation, neuronal fate is governed not by single molecular variables but by the joint configuration of interacting stability axes, whose progressive coupling reduces stability margins and drives the system toward a tipping boundary separating reversible from irreversible regimes. We further introduce an endogenous sensing layer (“Beacon”) that integrates distributed molecular signals into a latent estimate of system state. Rather than triggering deterministic responses, this Beacon-derived estimate modulates compensatory mechanisms probabilistically, such that response likelihood and strength increase as stability margins shrink, while remaining inherently stochastic. Within this framework, disease onset corresponds to a probabilistic crossing of an instability manifold, beyond which feedback amplification dominates and trajectories converge toward a pathological basin of attraction. This perspective provides a unified interpretation of heterogeneous neuronal vulnerability and supports the development of composite biomarkers and state-dependent therapeutic strategies. Together, this work reframes ALS as a problem of coupled instability and probabilistic control, linking TDP-43 molecular pathology to system-level dynamics and providing a principled conceptual foundation for prediction, stratification, and intervention. While conceptual, the framework is grounded in established mechanisms of TDP-43 pathology and principles from complex systems theory.