Tissue lamination state switches neuronal translocation from active to passive in the vertebrate retina

Abstract

Neuronal migration is essential for establishing functional tissue architecture in the developing central nervous system. While cell-intrinsic mechanisms driving neuronal movement have been identified, how migratory strategies adapt to dynamic developmental tissue changes remains less understood. Here, we address this question using retinal bipolar cells generated across unlaminated and laminated stages. This enables direct comparison of neuronal translocation across tissue states. Combining quantitative live imaging with targeted perturbations, we show that the migration mode of bipolar cells switches depending on tissue lamination state. Bipolar cells born before photoreceptor layer formation undergo directed, microtubule-dependent somal translocation. In contrast, later-born cells exhibit passive, non-directed displacement driven by collective tissue movements. Interference with tissue-wide movements impairs this displacement, while disrupting photoreceptor layer formation restores directed translocation. Independent of strategy, cells achieve accurate laminar positioning, indicating that tissue context determines neuronal migration mode, a principle likely relevant across the developing neural and other tissues.