Developmental Biology: A Very Short Introduction

Citation

Wolpert, L. (2011). Developmental Biology: A Very Short Introduction. Oxford University Press.

Chapter Summary

The book is number 280 in Oxford's Very Short Introductions series: an introduction and eleven short chapters in about 130 pages. The cover describes it as a concise account of what is known about development. It starts from the first steps of growth and covers one of the most active areas of biological research. The publisher introduces Wolpert as a distinguished developmental biologist; he is also the original author of the textbook now published as Wolpert's Principles of Development. The book moves from cells and whole embryos to particular processes and organ systems, and ends with regeneration and evolution.

Introduction

The introduction sets out the wonder of development: a fertilised egg about a tenth of a millimetre across contains the information to build a human being. It then sketches the history of embryology. Hippocrates explained development by heat and moisture. Aristotle posed the choice between preformation and epigenesis and favoured epigenesis. Preformationism dominated in the seventeenth century. The question was settled by the cell theory, by Weismann's idea that inheritance passes only through the germ cells, and finally by the discovery of DNA and genes coding for proteins.

Chapter 1: Cells

This chapter establishes the book's framework. Development results from the coordinated behaviour of cells, which is largely determined by the proteins each cell contains. Four processes are introduced: pattern formation, morphogenesis (change in form), cell differentiation and growth. The chapter explains that to understand genetic control of development, the genes specifically involved must be identified.

Chapters 2–3: Vertebrates; Invertebrates and plants

Chapter 2 follows vertebrate embryos through cleavage, the blastula or epiblast, gastrulation and the formation of the neural tube. It explains how the head-to-tail and back-to-belly axes are set up, how left–right asymmetry of internal organs arises, and how Hox genes give positional identity along the body. Chapter 3 turns to the fruit fly Drosophila, the nematode Caenorhabditis elegans and the plant Arabidopsis. Nematode cell fates are often specified cell by cell, rather than by gradients of signalling molecules. In plants, most structures are made after the embryo stage from meristems.

Chapters 4–6: Morphogenesis; Germ cells and sex; Cell differentiation and stem cells

Chapter 4 explains how animal embryos change shape during gastrulation through cell contraction, adhesion and division. It contrasts plants, where form arises from oriented cell division and expansion driven by internal pressure. Chapter 5 describes the functions of germ cells and the chromosomes and hormones of sexual development, in animals and in flowering plants. Chapter 6 explains differentiation as the result of patterns of gene activity controlled by transcription factors and chemical modification of DNA. It also discusses stem cells, blood formation and programmed cell death.

Chapters 7–8: Organs; Nervous system

Chapter 7 shows how positional information, specified by a gradient, can pattern organs. The examples are the vertebrate limb, the fly's adult appendages, insect and vertebrate eyes, the vascular system and the flower. Chapter 8 divides nervous system development into four stages: specifying neural identity, growing axons to their targets, forming synapses, and refining connections by eliminating branches and cells.

Chapters 9–11: Growth, cancer, and ageing; Regeneration; Evolution

Chapter 9 deals, as its title says, with growth and with what happens when growth control fails in cancer and as the body ages. Chapter 10 distinguishes two kinds of regeneration. In epimorphosis, a new structure grows, as in a salamander's limb. In morphallaxis, existing tissue is repatterned with little cell division, as in Hydra. Mammalian bone repair is also discussed. Chapter 11 argues that the evolution of multicellular animals and plants results from changes in embryonic development. These in turn come from genetic changes in when and where genes are expressed, and from new protein functions.

Key Concepts

Introduction and Chapter 1: Cells

• Epigenesis versus preformation: the historical question of whether embryonic structures arise progressively or exist from the start.
• Germ plasm: Weismann's idea that offspring inherit only through germ cells.
• The four developmental processes: pattern formation, morphogenesis, cell differentiation and growth.

Chapters 2–3: Vertebrates; Invertebrates and plants

• Body axes: the antero-posterior, dorso-ventral and left–right axes of the embryo.
• Gastrulation: the rearrangement of cell layers that lays down the body plan.
• Hox genes: genes that specify position along the head-to-tail axis.
• Mosaic development and meristems: cell-by-cell fate specification in nematodes, and continued growth from meristems in plants.

Chapters 4–6: Morphogenesis; Germ cells and sex; Cell differentiation and stem cells

• Cell adhesion and contraction: the cellular forces that shape animal embryos.
• Germ line: the only cells able to form a new organism in most animals.
• Transcription factors: proteins that control which genes are active in a given cell.
• Stem cells: cells that can renew themselves and give rise to specialised cell types.

Chapters 7–11: Organs; Nervous system; Growth, cancer, and ageing; Regeneration; Evolution

• Positional information: a cell's knowledge of where it is, often read from a gradient.
• Axon guidance and synaptic refinement: how neurons find targets and how connections are pruned.
• Epimorphosis and morphallaxis: regeneration by new growth versus repatterning of existing tissue.
• Evolution through development: changes in the timing and location of gene expression as a source of new forms.

Critical Analysis

Strengths

• Written by the author of a major textbook. The book distils the outlook of the original author of Principles of Development. Its emphasis on positional information and on the four basic processes gives readers a coherent way of thinking about any embryo.
• Comparative range in a small space. Vertebrates, flies, nematodes, a model plant, salamanders and Hydra all appear. Plants are compared with animals in several chapters (morphogenesis, germ cells, organs). Readers see both the general principles and the differences between organisms.
• Historical opening. The introduction places modern developmental biology in a long history of ideas, from Hippocrates and Aristotle to Weismann. This helps a newcomer see which questions the field was built to answer.
• Links beyond the embryo. Chapters on stem cells, cancer and ageing, regeneration and evolution show where developmental biology connects with medicine and evolutionary biology.

Limitations

• Published in 2011. Work since then on stem-cell reprogramming, organoids, genome editing and single-cell analysis is not covered.
• Very compressed. Eleven chapters in about 130 pages can only name the main processes. Molecular signalling pathways and experimental evidence are necessarily brief.
• Not a course text. The book is designed for quick orientation. It is not organised for systematic study in the way a course textbook is, and it cannot be relied on to prepare for an examination.

Where It Fits in the Course

This is the shortest book on the developmental biology list and the natural starting point. Jamie Davies's Life Unfolding is also written for general readers. It concentrates on the human body and on self-organisation, and runs to about three hundred pages; it suits readers who want a longer narrative after Wolpert. For a first course textbook, Slack and Dale's Essential Developmental Biology is a compact text that establishes general principles through a few model organisms. Barresi and Gilbert's Developmental Biology covers the major model organisms in more depth and connects development with evolution, regeneration, disease and the environment.

Wolpert's Principles of Development, now edited by Cheryll Tickle and colleagues, is the full-length descendant of Wolpert's own approach. It assumes prior cell and molecular biology and is the natural next step for readers who liked this book's framing. Carroll, Grenier and Weatherbee's From DNA to Diversity develops Wolpert's last chapter into a full account of how changes in developmental genes produce animal diversity.

How to Use This Book

School biology is enough background. The book suits students preparing for a first developmental biology course, students of other biological subjects who want an overview, and general readers.

• Read first: the Introduction and Chapter 1, which set up the four processes the rest of the book returns to.
• Core: Chapters 2–4 and 6–7. These cover embryos of the main model organisms, morphogenesis, differentiation and positional information, the material that every textbook builds on.
• By interest: Chapter 8 for neuroscience students; Chapters 6, 9 and 10 for those interested in stem cells and medicine; Chapter 11 for evolutionary biologists.
• Alongside a textbook: read the matching Wolpert chapter before each textbook unit. Afterwards, note which experiments and molecules the textbook adds to his outline.

Since the book dates from 2011, treat its account of stem cells and techniques as a starting point and update it from a recent textbook.