Table of Contents

Introduction

Part I Background

Chapter 1 Sex Differences in Disease
1.1. Males More Vulnerable at Every Age
1.2. Vulnerability of Males Leads to Sex-Specific Disease
1.3. Summary and Speculations

Chapter 2 Evolution of the Human Sex Chromosomes and a Portrait of the Human X
2.1. Chromosomal Basis of Sex Determination
2.2. The Human Sex Chromosomes Evolved from Reptilian Autosomes
2.3. Degeneration of the Y Chromosome
2.4. Ohno's Law and the Conservation of the Original X
2.5. Residual Homology and the Pseudoautosomal Regions
2.6. Genetic Portrait of the Human X
2.7. Summary and Speculations

Chapter 3 X Chromosome Dosage Compensation: An Overview
3.1. X Chromosome Dosage Compensation
3.2. Heterochromatin and Chromosome Silencing
3.3. Role in Sex Determination
3.4. Mechanisms of Dosage Compensation in Other Organisms
3.5. Mechanisms of Dosage Compensation in Mammals
3.6. Summary and Speculations

Chapter 4 The Discovery of X Chromosome Inactivation
4.1. The Lyon Hypothesis
4.2. General Scheme of Mammalian Dosage Compensation
4.3. Summary and Speculations

Chapter 5 Experimental Models for X Inactivation Studies
5.1. Spontaneous Human Mutations that Interfere with Inactivation
5.2. X-Linked Protein Variants Distinguish Parental Origin of X Chromosomes
5.3. Characterizing the Inactive X in Human Cell Cultures and Clones
5.4. Mouse-Human Hybrids Separate Inactive from Active X
5.5. Mouse Embryonic Stem Cells for Manipulating the Early Steps in X Inactivation
5.6. Transgenic Mice as a Functional Assay
5.7. Assays for X Inactivation Patterns in Heterozygotes
5.8. Summary and Speculations

Part II. Themes and Variations of X Inactivation

Chapter 6 Theme 1: The Initial Steps-Creating the Active and Inactive X
6.1. Characteristics of the Inactive X Chromosome
6.2. Time of Initiation in the Embryo
6.3. Cis Inactivation
6.4. The Master Control Region: XIC and Xist
6.5. Silencing the Inactive X Chromosome
6.6. Single Active X Versus X Inactivation
6.7. Choosing the Active X Chromosome
6.8. Summary and Speculations

Chapter 7 Theme 2: Subsequent Steps-Spreading and Maintaining Inactivation
7.1. Spreading Inactivation by Modifying Chromatin
7.2. Maintaining Inactivation by DNA Methylation of CpG Islands
7.3. Escape from Inactivation
7.4. Transient X Inactivation in Germ Cells
7.5. Induced X Reactivation in Placental Cells
7.6. Role of DNA Replication in X Inactivation
7.7. Summary and Speculations

Chapter 8 Variations 1: Evolution of the X Inactivation Center
8.1. Variations on the Themes of X Inactivation
8.2. Divergence in the Physical Map
8.3. The Effect of Map Changes on X Inactivation in Mouse and Man

Chapter 9 Variations 2: Stability of the Inactive X
9.1. Stability of X Inactivation & DNA Methylation
9.2 Genes that Escape Inactivation
9.3. Summary and Speculations

Chapter 10 Variations 3: Choice of Active X
10.1. Primary Nonrandom X Inactivation
10.2. Paternal X Inactivation
10.3. Relationship of Paternal X Inactivation to Genomic Imprinting
10.4. Does Antisense Transcription Have a Role?
10.5. Evolution and Tinkering
10.6. Effect of Inactivation Timing
10.7. Summary and Speculations

Part III. Medical Consequences of X Inactivation

Chapter 11 The Single Active X
11.1. Coping with a Monosomy X
11.2. Dosage Compensation of the Active X
11.3. Sex Differences in Susceptibility to Disease
11.4. Viability of Turner Syndrome, Klinefelter Syndrome, and X Chromosome Aneuploidy
11.5. X Deletions, Ring X Chromosomes, X Duplications, and Functional Disomy
11.6. X/Autosome Translocations and Spreading of Inactivation
11.7. Polyploidy and the Choice of Active X
11.8. Summary and Speculations

Chapter 12 Mosaicism
12.1. The X-Linked Phenotype Is Dominant at the Cellular Level
12.2. Females Are Mosaics
12.3. Interaction between Mosaic Cell Populations
12.4. Skewing of X Inactivation Patterns
12.5. Effect of X Inactivation on Clinical Phenotype
12.6. "Manifesting" Heterozygotes
12.7. Summary and Speculations


Chapter 13 Epimutations, Chromatin Disorders and Sex Differences in Phenotype
13.1 Epimutations Usually Cause Somatic Diseases
13.2 Epimutations in Imprinting Disorders
13.3 Epigenetic Regulation of Autosomal Gene Expression by Sex Chromosomes
13.4 Disorders of the Epigenetic Machinery
13.5 Sex Differences in Manifestations of Chromatin Disorders
13.6 Treatment of Chromatin Disorders
13.7 Summary and Speculations

Chapter 14 Determinants of Female Phenotypes
14.1. The Dynamic Effect of Interacting Cell Populations on the Health of Females
14.2. The Effect of X Inactivation on Normal Female Phenotype and Cell Diversity
14.3. Epilogue

Appendix A Descriptions of Model X-linked and Other Relevant Diseases
Appendix B Sex Chromosome Aneuploidy, Polyploidy, and Parthenogenetic Conceptuses
Appendix C Effect of X Inactivation on Phenotype and Cell Selection in X-linked Disorders

Glossary
References
Index

About the Author

Barbara Migeon, MD, is Professor in the McKusick-Nathans Institute of Genetic Medicine and the Department of Pediatrics at the Johns Hopkins School of Medicine. She had fellowships in pediatrics, endocrinology and genetics and is board certified in pediatrics, biochemical genetics and cytogenetics. She was the founding director of the Hopkins PhD Program in Human Genetics. Her research has been focused on the molecular mechanisms of X inactivation
in human cell and the clinical consequences of the single active X chromosome.

Reviews

"This book provides a balanced overview of the field to date, allowing newcomers to the field to concentrate on the recent literature necessity...The information in the book is up-to-date and a superb introduction to the entire field for gradutate students and fellows."--Nature
"I thoroughly enjoyed reading this book...This important and enjoyable book should be read by physicians who care for women of all ages."--New England Journal of Medicine
"Migeon's eyewitness account of the discovery of X inactivation and the investigations of its mechanism is engaging...Biologists will appreciate the breadth of the book and the thorough referencing."--Science
"This is a magnificent discussion of the X chromosome function, mechanisms of expression, and the role of the X chromosome in embryogenesis and human pathology. Congratulations are due to Dr. Migeon for a job well done. This is a unique book
with very few omissions. Reading it is a pleasure and the author adheres to her goals and provides unique information in a manner I have not seen before. This book has no comparison and I look forward to updated editions." --Doody's