MRC National Institute for Medical Research, London
Science for Health
2009 meeting - Making an embryo from a fertilised egg
Making an embryo from a fertilised egg is one of the most complicated phenomena the human mind has ever contemplated. Using instructions encoded by the genome, an organisation gradually emerges in which the position of head and tail, inside and outside, or right and left, are defined in outline and then in increasing detail. Developmental biologists have made huge advances in understanding these processes at a molecular level in the last three decades. Remarkably, many of the proteins involved have homologues that perform similar functions throughout the animal kingdom. Our speakers are well known for their important and distinctive contributions to our growing understanding of how order emerges in embryos.
How cells of the embryo become different from each other - Professor Jim Smith FRS
Almost twenty years ago, Jim Smith discovered a protein called activin that could make undifferentiated cells form specialised tissues such as muscle, blood or nervous tissue depending on its concentration. Activin was the first of a group of proteins with similar properties that are called morphogens because they play a critical role in establishing the morphology and shape of an early embryo. The key idea is that a gradient of declining morphogen concentration is generated around a discrete source within the embryo and this induces a characteristic spatial pattern of different tissue types. There is now evidence that morphogens diffuse through intercellular space, and that receptors on target cells interpret the concentration as a simple binary choice: to switch a gene on or not. Many morphogens cooperate in creating the detailed organisation of an embryo.
How brain tissue sub-divides into functionally distinct units - Dr David Wilkinson
A sheet of tissue that develops on the surface of vertebrate embryos is the starting point for creating the phenomenally complex architecture of the brain and spinal cord. The next step is to subdivide the tissue into building blocks with sharply defined borders, each with a distinctive identity that will underpin the formation of a set of nerves with distinct and specific functions. In the prospective hindbrain, these segments, known as rhombomeres, express a characteristic set of genes in alternate segments. Early in development of the hindbrain, when cells are acquiring an identity, they cannot migrate from one rhombomere into another; presumably ensuring that each segment is not corrupted by cells with inappropriate identities. David discovered this is achieved by a novel mechanism involving cell surface receptors that makes cells from adjacent rhombomeres repel each other. This mechanism is important elsewhere in the body for creating and maintaining correct organisation; when it becomes defective, it contributes to the spreading of cancer cells.
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