Book contents
- Frontmatter
- Contents
- Preface
- Acknowledgements
- Read me first …
- Glossary
- Dedication
- Introduction: A disease for every gene?
- I From molecular biology to human genetics
- II From molecular genetics to human biochemistry
- III From molecular biochemistry to human cell biology
- IV From molecular cell biology to human physiology
- 16 Development
- 17 Metabolism
- 18 Blood
- 19 Immunity
- 20 Neurobiology
- V From molecular physiology to human molecular biology
- Index
16 - Development
Published online by Cambridge University Press: 01 June 2011
- Frontmatter
- Contents
- Preface
- Acknowledgements
- Read me first …
- Glossary
- Dedication
- Introduction: A disease for every gene?
- I From molecular biology to human genetics
- II From molecular genetics to human biochemistry
- III From molecular biochemistry to human cell biology
- IV From molecular cell biology to human physiology
- 16 Development
- 17 Metabolism
- 18 Blood
- 19 Immunity
- 20 Neurobiology
- V From molecular physiology to human molecular biology
- Index
Summary
The molecular narrative of how life begins is one of the most fascinating in biology. How does a multifaceted organism arise from an amorphous cell mass? How are patterns imposed on tissues arising from a common cellular progenitor? And what genetic constellations determine phenotypes as diverse as blue eyes, a left-sided heart, or an artistic temperament?
Embryonic induction
Life begins when egg integrins meet sperm ADAMs
Embryogenesis is initiated by a five-step process: chemoattraction of sperm to the egg; sperm–egg surface binding; discharge of sperm vesicle contents onto the egg surface (acrosome reaction); sperm penetration of the egg-coat; and fusion of sperm-egg membranes, permitting restoration of the diploid genome.
Mature ova attract sperm by releasing subpicomolar chemotactic factors within the female genital tract. Spermatozoa lured to the egg by speciesspecific chemoattractants are first made hypermotile by bicarbonate-induced cAMP signaling, then activated by egg-coat extracellular matrix ZP3 (zona pellucida) oligosaccharides that bind human-specific galactosyltransferases on the sperm surface. Membrane clustering of these enzymes activates sperm sensor G-protein-coupled receptors, causing transmembrane influx of sodium ions; this is followed by tyrosine phosphorylation of the ZP3 receptor, leading in turn to sperm pronuclear binding of the ZP2 receptor in the inner membrane leaflet (Figure 16.2). Nitric oxide synthase from activated sperm stimulates a wave of egg nitrosation within seconds of fertilization, thereby activating egg development. Mobilization of calcium follows diffusion of the sperm calcium-regulatory protein oscillin into the ovum.
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- Chapter
- Information
- Human Molecular BiologyAn Introduction to the Molecular Basis of Health and Disease, pp. 391 - 414Publisher: Cambridge University PressPrint publication year: 2002