Spontaneous Curvature Sculpts Filament-Vesicle Morphogenesis.

Membrane-bound filaments are central to cellular morphogenesis, yet how spontaneous curvature regulates filament-membrane coupling under geometric confinement remains unclear. Here we show that spontaneous curvature fundamentally reorganizes filament-membrane morphogenesis in vesicles by biasing the competition between membrane deformation and filament bending. Using a unified curvature-elasticity framework that couples membrane and filament curvature energetics, we construct phase diagrams for vesicles enclosing filament loops and demonstrate that spontaneous curvature selects distinct symmetry-breaking pathways, leading to both continuous and discontinuous morphological transitions. In the rigid-filament limit, we further identify an intrinsic accommodation limit imposed by membrane elasticity together with area and volume conservation, beyond which no mechanically equilibrated configuration exists. These findings establish spontaneous curvature as a powerful design parameter for programming filament-membrane morphogenesis in biological and synthetic systems.