Johnson 2009 egg-blast

Johnson 2009 egg-blast - From Mouse Egg to Mouse Embryo:...

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Unformatted text preview: From Mouse Egg to Mouse Embryo: Polarities, Axes, and Tissues Martin H. Johnson Department of Physiology, Development, and Neuroscience and the Center for Trophoblast Research, The Anatomy School, Cambridge CB2 3DY, United Kingdom; email: mhj21@cam.ac.uk Annu. Rev. Cell Dev. Biol. 2009. 25:483512 First published online as a Review in Advance on July 20, 2009 The Annual Review of Cell and Developmental Biology is online at cellbio.annualreviews.org This articles doi: 10.1146/annurev.cellbio.042308.113348 Copyright c 2009 by Annual Reviews. All rights reserved 1081-0706/09/1110-0483$20.00 Key Words trophoblast, inner cell mass, blastocyst, PAR genes, ezrin, Cdx2 Abstract This review describes the three classical models (mosaic, positional, and polarization) proposed to explain blastocyst formation and summarizes the evidence concerning them. It concludes that the polarization model incorporates elements of the other two models and best explains most known information. I discuss key requirements of a molecular basis for the generation and stabilization of polarity and identify ezrin/E- cadherin, PAR proteins, and Cdx2 as plausible key molecular players. I also discuss the idea of a network process operating to build cell al- locations progressively into committed differences. Finally, this review critically considers the possibility of developmental information being encoded within the oocyte and zygote. No final decision can be reached on a mechanism of action underlying any encoded information, but a cell interaction process model is preferred over one that relies solely on differential inheritance. 483 A n n u . R e v . C e l l D e v . B i o l . 2 9 . 2 5 : 4 8 3- 5 1 2 . D o w n l o a d e d f r o m w w w . a n n u a l r e v i e w s . o r g b y S t a t e U n i v e r s i t y o f N e w Y o r k- S t o n y B r o o k o n 9 / 1 6 / 1 . F o r p e r s o n a l u s e o n l y . Contents INTRODUCTION . . . . . . . . . . . . . . . . . . 484 THE EXPANDED BLASTOCYST: BACKGROUND. . . . . . . . . . . . . . . . . . 484 Time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 484 Morphological Transitions, Shapes, and Axes. . . . . . . . . . . . . . . . 485 Cell Lineages . . . . . . . . . . . . . . . . . . . . . . 486 THE THREE MODELS PROPOSED TO EXPLAIN HOW A BLASTOCYST IS GENERATED . 488 The Mosaic Model. . . . . . . . . . . . . . . . . 488 The Positional Model . . . . . . . . . . . . . . 489 The Polarization Model . . . . . . . . . . . . 489 REEVALUATION OF THE THREE MODELS AND THEIR RELATIONSHIPS . . . . . . . . . . . . . . . . 491 MOLECULAR BASIS OF POLARITY GENERATION AND STABILIZATION. . . . . . . . . . . 492 E-Cadherin, -Catenin, Actin, Ezrin, and Laminin/Integrins. . . . 492 PAR Proteins . . . . . . . . . . . . . . . . . . . . . . 494 CDX2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 495 SUMMARY . . . . . . . . . . . . . . . . . . . . . . . . . . 496 DOES POSITIONAL INFORMATION EXIST WITHIN THE EGG OR ZYGOTE? . . . . . . . . . . . . . . . . . . . . . . . . 497ZYGOTE?...
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Johnson 2009 egg-blast - From Mouse Egg to Mouse Embryo:...

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