| Citation | Making use of novel and very precise methods, Lawrence has made a detailed analysis of cell lineage in developing insect epidermis. He has made a major contribution to our understanding of the arrangement of cells and their products in development. His early experiments made an extensive analysis of cuticular structures resulting from the transplantation of pieces of abdominal epidermis in Oncopeltus and Rhodnius. He showed that the polarity of cuticular structures could be wholly explained by assuming that the diffusion of one substance in one direction gives a gradient of morphogenetic values. He also showed that the cuticular differentiation of cells is an adjacent segment. Cells in adjacent segments were shown to be separated by lineage from an early embryonic stage, but not by the absence of gap junctions or electric coupling. His experiments starting in 1971 provided the strongest evidence yet for Garcia-Bellido's (1973) concept of developmental compartments. In particular Lawrence was the first to demonstrate compartment -specific gene expression by showing that the engrailed mutation in Drosophila effects only posterior wing structures. His more recent work has established the existence of dorsal and ventral compartments, as well as the widespread occurrence of compartments in non-thoracic segments such as those comprising the head and abdomen. |