Multicellular plants and animals consist of a precise arrangement of different types of cells. These cells are grouped into organs and tissues that are specialised to carry out particular roles. This complicated organisation is formed progressively as the embryo develops, starting from a single cell, the fertilised egg. Developmental biologists study the mechanisms underlying this remarkable transformation of a single cell into a complex organism.
This brief guide describes why developmental biology is relevant to us, what happens during development, how development is studied, some general principles that have been discovered, and its’ relationships with other fields of biology.
[toggle title_open=”Why is developmental biology relevant?” title_closed=”Why is developmental biology relevant?” hide=”yes” border=”yes” style=”default” excerpt_length=”0″ read_more_text=”Read More” read_less_text=”Read Less” include_excerpt_html=”no”]In addition to being a fascinating subject, developmental biology has great practical relevance for us humans. By studying the development of a living organism we can understand the steps required to build all of its organs and tissues. We are not able to observe in detail the development of a human embryo inside the mother, and for obvious ethical reasons, we do not perform experiments on these embryos.
It has been discovered that many important mechanisms of development are the same in all types of animals. Knowledge of how other animals develop will allow us to understand how some human diseases are caused by defects in development, and how to repair our body when some of its parts are not functioning due to disease or damage.
Why is that?
If a car begins to show some problems, the mechanic who knows how its parts fit together to make it function will be able to identify what went wrong and which parts need restoring in order to resolve the problems. Similarly, discoveries by developmental biologists of how, for instance, a liver is built, will enable us to find better ways to cure diseases affecting the development or maintenance of that organ.[/toggle]
[toggle title_open=”What happens during development?” title_closed=”What happens during development?” hide=”yes” border=”yes” style=”default” excerpt_length=”0″ read_more_text=”Read More” read_less_text=”Read Less” include_excerpt_html=”no”]During development, an initially simple structure progressively transforms into a more complex one. The amazing nature of this transformation can be seen by looking at early steps of development in which a complicated and precise pattern forms in a short period of time: see the movie of the first 17 hours of zebrafish development.
[zebrafish movie and acknowledgement]
RO Karlstrom and DA Kane (1996) Development 123:461, with permission of the Company of Biologists.
The formation of this complex pattern involves a number of processes that are tightly coordinated with each other. What these processes are can be illustrated by thinking about the structure of your arm:
- It has many different types of cells that make the tissues (skin, bones, nails…).
- These cells and tissues are all in the correct location (skin and nails on the outside, bones on the inside), with differences in their organisation from shoulder to finger tips, thumb to little finger, front to back.
- There is the correct number of the different types of cells.
- Each of the tissues has the correct shape.
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Since organisms are incredibly complicated, achieving a complete understanding of how they develop is a major challenge. Advances are made by addressing specific questions that are less difficult. For example, how is the overall organisation of body tissues formed? How do chambers and valves form to make a functioning heart? How does the nervous system get wired up? How do flowers, leaves and roots form? What underlies general features of development, such as the formation of cell types at the correct places? How is the size of each tissue and the organism as a whole correctly controlled? To address these questions, studies are carried out at the level of tissues, cells, and their molecular components in order to discover:
- Which genes control development
- The functions of each gene
- Which cells each gene is active in
- The normal destiny of a particular cell
- How the destiny of a cell is controlled
- How tissues are assembled
The methods used to investigate development include genetic screens, alteration of the functions of specific genes, labelling and transplantation of cells, and visualisation of cells and molecules in living tissues.
[toggle title_open=”What are model organisms?” title_closed=”What are model organisms?” hide=”yes” border=”yes” style=”default” excerpt_length=”0″ read_more_text=”Read More” read_less_text=”Read Less” include_excerpt_html=”no”]Most developmental biology studies focus on specific organisms that have been chosen as models. This is partly for a historical reason, since previous work that accumulates knowledge of one particular organism is a basis for the next experiments. Another reason is that different organisms have distinct experimental advantages.[/toggle]
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Studies of the development of many different organisms have uncovered a number of general principles, including:
- Many mechanisms are conserved between diverse organisms. Consequently, findings that can be made more rapidly in simple organisms, such as fruitflies, help in understanding more complicated ones, such as humans.
- During development, most cells become progressively more restricted in what type of cell they can form. However, stem cells in embryos and adult tissues retain the ability to form a wide range of cell types.
- Some proteins that turn genes on or off are switches for the formation of particular types of cells, such as nerve cells and muscle cells.
- Signalling between cells is essential as it coordinates developmental processes, induces cell types to form, and controls the organisation of cells within tissues.
- Molecules interact to form circuits and by uncovering these circuits we can understand important aspects of development. The circuits can be positive (self-reinforcing) or negative (self-inhibitory) and underlie the decision making of cells.
For Developmental Biologists
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UK societies whose work is closely related to that of the BSDB:
- American Association for the Advancement of Science (AAAS)
- American Society for Biochemistry and Molecular Biology
- American Society for Cell Biology (ASCB)Asia-Pacific Developmental Biology Network (APDBN)
- The Anatomical Society of Great Britain and Ireland
- Biochemical Society (UK)
- British Association for the Advancement of Science
- British Biophysical Society
- British Pharmacological Society
- British Society for Immunology
- Federation of American Societies for Experimental Biology (FASEB)
- German Society of Developmental Biology
- Institute of Biologists
- International Society of Developmental Biologists
- National Centre for 3Rs (NC3Rs)
- Save British Science (SBS)
- Scottish Developmental Biology Group
- Society for Developmental Biology, USA (SDB)
- Société Français de Biologie du Développement (SFBD)
- Spanish Society of Developmental Biology
- The Society For Experimental Biology (SEB)
- The Society of Systematic Biologists, USA
- UK Life Sciences Committee (UKLSC)
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- The Society for Developmental Biology has a Virtual Library and tutorials, books, and teaching aids
- Biosciences Virtual Library
- FlyBase the Drosophila database
- Flyview: the Drosophilia gene expression database
- The Berkeley Drosophila Genome Project : access to lots of different information on Drosophila
- WormBase: the Caenorhabditis elegans database
- Caenorhabditis elegans WWW server at University of Texas Southwestern Medical Center
- Zebrafish Information Server at the University of South Carolina
- The Xenopus Molecular Marker Resource
- The Kidney Developmental Database
- Tbase: the database of transgenic and targeted mice
- The Mouse Atlas Project
- The Chick EST project at UMIST