Unsupervised prepatterning in multicellular morphogenetic circuits

Pattern acquisition in morphogenetic signaling circuits may proceed through instruction-driven or instruction-free mechanisms, distinguished by the presence of exogenous cues. In developing epithelia, adaptive morphogenesis is known to reshape tissue architecture, but whether this arises from guided or spontaneous learning remains unresolved. Here we imaged voltage, calcium and transcriptional dynamics from up to 90,000 cells simultaneously in primary surface ectoderm (PSE) and higher-order blastemal zones (HBZs) while axolotl limb rudiments experienced repeated mechanical-strain tasks, as well as during unrewarded exposure to identical stimuli. As in earlier work, cellular state changes in task cohorts tracked the ensuing morphological improvements. Strikingly, nearly identical changes emerged in cohorts receiving only unrewarded exposure, indicating that the underlying plasticity resulted largely from unsupervised prepatterning. The highest plasticity was observed in medial HBZs and followed biochemical, rather than purely positional, learning rules. Only in task cohorts did we detect a ramping insulin-like growth-factor signal in anterior HBZs, consistent with a supervised reinforcement channel. The cellular data predicted that prior unsupervised exposure should accelerate later, reward-contingent morphogenesis; targeted regenerative assays confirmed this acceleration in vivo. These findings position spontaneous prepatterning as a key driver of competent, rapidly adaptable regeneration and suggest leveraging unsupervised regimes to prime tissues for therapeutic remodeling.