Modifying gastruloids to dissect mechanisms of tissue-specific induction.

How functional organisms arise from a single cell is a fundamental question in biology with direct relevance to understanding developmental defects and diseases. Dissecting developmental processes provides the basic, critical framework for understanding disease progression and treatment. Bottom-up approaches to recapitulate formation of various components of the embryo have been effective to probe symmetry-breaking, self-organisation, tissue patterning and morphogenesis. However, these studies have been mostly concerned with axial patterning, which is essentially longitudinal. Can these models generate the appendicular axes? If so, how far can self-organisation take these? Will experimentally induced organisers be required? This short review explores these questions, highlighting how minimal models are essential for understanding patterning and morphogenetic processes.