Cutting, pasting and painting: experimental embryology and neural development: Development

Key Points This article briefly discusses the role of experimental embryology (and experimental embryologists) in discovering the principles of vertebrate neural development. It provides a historical account of the roles of cutting, pasting and painting, as well as modifications of these techniques that have led to new approaches, in elucidating the principles of neural development. Experimental embryologists have mainly used four vertebrate models to work out the principles of neural development: amphibians, chicks, mice and zebrafish. The strengths and weaknesses of these four vertebrate models are discussed. Experimental embryology is founded on three main techniques. 'Cutting' involves either ablation — the removal and discarding of a tissue, a group of cells or single cells to test whether they are required for a particular developmental event — or the isolation of tissues and cells for further testing. 'Pasting' involves transplanting tissues or cells from donor to host embryos. 'Painting' involves the use of labelled cells for the purpose of tracking cell movements and fates during further development. The central principle of vertebrate neural development is that the nervous system and associated structures, such as the nose, eyes, ears and (in some organisms) lateral line, arise through a series of inductive interactions between neighbouring cells. The use of cutting, pasting and painting by experimental embryologists has revealed several key principles of neural development that are related to the central principle. The techniques of experimental embryology have contributed to the elucidation of a number of principles of vertebrate neural development. This review outlines the crucial series of experiments that led to the discovery of neural induction, and recent modifications of experimental embryological techniques that have been used to begin to work out its molecular mechanisms. The goal of experimental embryology seems rather simple: to manipulate embryos in systematic ways to elucidate mechanisms of development. Such manipulation involves variations in three main techniques — cutting, pasting and painting — and all three techniques have contributed enormously to the establishment of key principles of neural development.