Lecture 2 - The Medium and the message
Generating different cell types will not make an animal. Arms and legs have the same cell types - muscle, bone and so on - yet are different. We differ from birds and sheep and chimpanzees, not so much because of cell types but because of how they are spatially patterned. How do the cells know what to do?
Some embryos can still form normal patterns when parts are removed or rearranged at early stages. If the early eye region of the frog embryo is grafted elsewhere in the embryo it behaves like the region to where it is placed. However, at a later stage it will develop as an eye even if grafted into the belly. Pattern formation and regulation can be thought of in terms of the French Flag Problem. How could a line of cells, each of which can become blue, white or red, become self organizing so as to look like the French Flag? A simple solution is that they know their position and interpret it according to a set of instructions which is common to every cell.
The development of an angel's wing can be thought of in terms of positional information. Different mechanisms provide the cells with knowledge of their position as if they were in a coordinate system. Frankenstein would be encouraged that the signals between cells may be a universal and simple language.
Communication between tissues coordinates development. Some of this communication is instructive. If the sheet of cells that would normally form the sole of the foot is combined with a tooth germ it forms enamel.
About the 1986 CHRISTMAS LECTURES
In the 1986 CHRISTMAS LECTURES, Professor Lewis Wolpert (1929-2021) explores developmental biology in a series titled 'Frankenstein's Quest'. Quoting the fictional Dr Frankenstein: "After days and nights of incredible labour and fatigue, I succeeded in discovering the cause of generation and life..." These lectures will look at how life really is generated.
All life comes from cells and all the animals we see about us come from just one cell, the fertilized egg. How does the egg give rise to bats and boys, gnats and girls, eyes and arms? The egg divides and gives rise to many cells which move, multiply, change, and communicate, and from these activities animals emerge through embryonic development. Like an imaginary Frankenstein, we will explore what we need to know in order to control development in order to create not a monster, but an angel.