CONTENTS Cranial Placodes 389 Vertebrae formation 431 U SIDELIGHTS SPECULATIONS Cranial Neural Crest C Dorsal Aorta Formation 432 Migration and Specification 391 Tendon Formation: The Syndetome 432 NEURONAL SPECIFICATION AND AXONAL INTERMEDIATE MESODERM: THE UROGENITAL SPECIFICITY 392 SYSTEM 434 The Generation of Neuronal Diversity 393 The Progression of Kidney Types 434 Pattern Generation in the Nervous System 394 Specification of the Intermediate Mesoderm Cell adhesion and contact guidance by attraction Pax2/8 and Lim1 435 and repulsion 396 Guidance by diffusible molecules 398 Reciprocal Interactions of Developing Kidney Tissues 436 Target selection 399 Mechanisms of reciprocal induction 437 Forming the synapse: Activity-dependent Coda 442 development 402 Differential survival after innervation: Neurotrophic factors 403 CHAPTER 12 H SIDELIGHTS SPECULaTIoNs The Brainbow 404 Paths to glory: The travels of the retinal ganglion Lateral Plate Mesoderm and the axons 404 Endoderm 445 The Development of Behaviors: Constancy and Plasticity 408 LATERAL PLATE MESODERM 445 Heart Development 446 CHAPTER 11 Specification of heart tissue 446 Migration of cardiac precursor cells 448 Paraxial and intermediate Determination of anterior and posterior cardiac Mesoderm 413 domains 450 Heart cell differentiation 450 PARAXIAL MESODERM: THE SOMITES AND Fusion of the heart rudiments and initial heartbeats THEIR DERIVATIVES 414 Formation of the Somites 415 Looping and formation of heart chambers 453 Periodicity of somite formation 417 I S/DELIGHTS SPECULATIONS Redirecting Blood Flow in the Newborn Mammal 455 Where somites form: The Notch pathway 417 I SIDELIGHTS SPECULATIONS Coordinating Waves and Formation of Blood Vessels 456 Clocks in Somite Formation 419 Constraints on the construction of blood vessels 456 Separation of somites from the unsegmented Vasculogenesis: The initial formation of blood mesoderm 420 ls458 Epithelialization of the somites 420 Angiogenesis: Sprouting of blood vessels and Somite specification along the anterior-posterior remodeling of vascular axis 420 Arterial and venous differentiation 462 Differentiation of the somites 421 Determination of the sclerotome 424 Anti-angiogenesis in normal and abnormal Determination of the central dermamyotome 425 Determination of the myotome 425 The lymphatic vessels 465 Myogenesis: The Generation of Muscle 426 Hematopoiesis: The Stem Cell Concept 466 Myogenic bHLH proteins 426 Sites of hematopoiesis 466 Specification of muscle progenitor cells 426 Committed stem cells and their fates 468 Hematopoietic inductive microenvironments 47( Osteogenesis: The Development of Bones 428 Stem cell niche construction 470 Endochondral ossification 428xii CONTENTS Cranial Placodes 389 • SIDELIGHTS & SPECULATIONS Cranial Neural Crest Cell Migration and Specification 391 NEURONAL SPECIFICATION AND AXONAL SPECIFICITY 392 The Generation of Neuronal Diversity 393 Pattern Generation in the Nervous System 394 Cell adhesion and contact guidance by attraction and repulsion 396 Guidance by diffusible molecules 398 Target selection 399 Forming the synapse: Activity-dependent development 402 Differential survival after innervation: Neurotrophic factors 403 • SIDELIGHTS & SPECULATIONS The Brainbow 404 Paths to glory: The travels of the retinal ganglion axons 404 The Development of Behaviors: Constancy and Plasticity 408 CHAPTER 11 Paraxial and Intermediate Mesoderm 413 PARAXIAL MESODERM: THE SOMITES AND THEIR DERIVATIVES 414 Formation of the Somites 415 Periodicity of somite formation 417 Where somites form: The Notch pathway 417 • SIDELIGHTS & SPECULATIONS Coordinating Waves and Clocks in Somite Formation 419 Separation of somites from the unsegmented mesoderm 420 Epithelialization of the somites 420 Somite specification along the anterior-posterior axis 420 Differentiation of the somites 421 Determination of the sclerotome 424 Determination of the central dermamyotome 425 Determination of the myotome 425 Myogenesis: The Generation of Muscle 426 Myogenic bHLH proteins 426 Specification of muscle progenitor cells 426 Myoblast fusion 427 Osteogenesis: The Development of Bones 428 Endochondral ossification 428 Vertebrae formation 431 Dorsal Aorta Formation 432 Tendon Formation: The Syndetome 432 INTERMEDIATE MESODERM: THE UROGENITAL SYSTEM 434 The Progression of Kidney Types 434 Specification of the Intermediate Mesoderm: Pax2/8 and Lim1 435 Reciprocal Interactions of Developing Kidney Tissues 436 Mechanisms of reciprocal induction 437 Coda 442 CHAPTER 12 Lateral Plate Mesoderm and the Endoderm 445 LATERAL PLATE MESODERM 445 Heart Development 446 Specification of heart tissue 446 Migration of cardiac precursor cells 448 Determination of anterior and posterior cardiac domains 450 Heart cell differentiation 450 Fusion of the heart rudiments and initial heartbeats 452 Looping and formation of heart chambers 453 • SIDELIGHTS & SPECULATIONS Redirecting Blood Flow in the Newborn Mammal 455 Formation of Bloodvessels 456 Constraints on the construction of blood vessels 456 Vasculogenesis: The initial formation of blood vessels 458 Angiogenesis: Sprouting of blood vessels and remodeling of vascular beds 461 Arterial and venous differentiation 462 Organ-specific capillary formation 463 Anti-angiogenesis in normal and abnormal development 465 The lymphatic vessels 465 Hematopoiesis: The Stem Cell Concept 466 Sites of hematopoiesis 466 Committed stem cells and their fates 468 Hematopoietic inductive microenvironments 470 Stem cell niche construction 470