Head and jawsF07 - Joint formation (continued) Wnt14 GDF5...

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Unformatted text preview: Joint formation (continued) Wnt14 GDF5 Normal wing Wnt14 injected Normal mouse Noggin -/- mutant Noggin Wnt14 inhibits Sox9, the inducer of Col2a1. This suppresses chondrocyte formation and induces GDF5 GDF5 is required for joint formation (mutant lacks joints) Noggin is expressed throughout cartilage condensation & is required for joint formation (mutant lacks joints) Noggin, a Bmp antagonist, allows chondrocytes to respond to joint-inducing signals and blocks activity of BMPs. However, Wnt14 suppresses Noggin expression, & GDF5 antagonizes Noggin protein. As noggin is required to sense, joint Inducing signal, a new joint can Form only at a distance from inhibitory signal Joint Formation (again) Evolution of the vertebrate head skeleton: the tale of the neural crest Major Derivatives of the Ectoderm Germ Layer Regions of the neural crest Cranial - branchial arches, melanocytes, cranial bones & cartilages Cardiac S1-S3: walls of large arteries, septum that divides aorta from pulmonary circulation. Trunk S6 S28: melanocytes Sensory ganglia, sympathetic ganglia, adrenal medulla, Vagal S1-S7 and Sacral posterior to S28: Parasympathetic (enteric) ganglia of gut Neurulation with reference to formation of neural crest cells Neural Crest Neural Crest Neural crest tissue found ONLY IN VERTEBRATES. Often called the 4th germ layer. Forms melanocytes, much of the head skeleton, peripheral glial cells, peripheral & autonomic neurons, and chromaffin cells of the adrenal gland cells. Epithelial cells at margin of neural plate become migratory (amoeboid). Skull development is modular Neurocranium : Cartilagenous; Skull vault and base. Neural crest derived, except for parietal bone, which forms head mesoderm . Encloses brain and sense organs. Sensory capsules: Otic, Nasal, Optic. Dermatocranium : Bone (dermal). Neural crest origin, Bony plates of the skull. Viscerocranium : Cartilagenous; Neural crest derived. Pharyngeal arches. Fate map of neural crest shows its contribution to skull. Wnt1, a neural crest marker, was used to irreversibly activate a reporter gene in mouse neural crest. Blue shows cells that have expressed Wnt1 during their life....
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Head and jawsF07 - Joint formation (continued) Wnt14 GDF5...

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