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Biology 4361 Neural Crest Cells July 24, 2008
Neural Crest ­ Overview Neural crest derivatives NC cell specification and migration NC regions Trunk Vagal Cranial
Cardiac Ectodermal Derivatives Neural crest – “4 th germ layer”
Neural Crest Derivatives T. Halliday, 1980 Michael Sereda, M. D.
J. Briscoe Styracosaurus albertensis © Franco Andreone Lora Bryson Neural Crest Derivatives
Neural Crest Cells Neurons, Schwann cells, pigment cells Initiation – interactions between neural plate and presumptive epidermis ­ NC undergos epithelial­to­mesenchymal transformation ­ stimulated by Wnts, BMPs, FGFs
Neural Crest Migration S.J Kimber Migration pathways are controlled Soluble factors also control migration of certain NC cell populations; e.g. by extracellular matrices and by glial­derived neurotrophic factor chemotactic factors ­ permissive and instructive signals ­ produced by the gut mesenchyme attracts vagal and sacral NC cells
­ negative signals also Neural Crest Regions Cranial midbrain forebrain hindbrain Vagal (named after the vagus nerve – innervates the heart)
Cardiac Trunk Sacral Trunk Neural Crest midbrain forebrain hindbrain Two migration pathways: Ventrolateral – early migration; into and through the anterior (not posterior) half of each somite ­ cells that remain in the somite = dorsal root ganglia (sensory neurons) Vagal ­ cells that travel through the somite form sympathetic ganglia, adrenal medulla, aortic nerve clusters Ventrolateral Sacral somite
Trunk Neural Crest midbrain forebrain hindbrain Vagal Two migration pathways:
Ventrolateral – early migration; into and through the anterior (not posterior) half of each somite Dorsolateral – later migration; travel between ectoderm and somite mesoderm; later move into epidermis ­ form melanocytes Ventrolateral Sacral Dorsolateral Vagal and Sacral Neural Crest Cranial midbrain forebrain hindbrain Cardiac Vagal and sacral neural crest cells generate the parasympathetic (enteric) ganglia of the gut Trunk
Cranial Neural Crest Cranial
midbrain forebrain hindbrain Cranial (cephalic) neural crest cells form craniofacial mesenchyme; creates (among others) ­ facial cartilage and bone ­ cranial neurons ­ glia ­ connective tissue Cranial NC cells also enter pharyngeal arches and pouches; form ­ thymic cells ­ odontoblasts of tooth primordia ­ bones of the middle ear and jaw Cranial NC Migration into Pharyngeal Arches Pharyngeal arches Neural crest cell migrate into pharyngeal arches 1
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Human embryo 31 d Mammalian Facial Development NC cells contribute: skeletal elements (face, hyoid, etc.) cartilage elements (e.g. in trachea) inner ear bones cranial nerves (V, VII, IX, X,)
Nasal placode upper and lower jaws Stomodeum Neural Crest Cells in Head and Face
Bone – Intramembranous Ossification Cranial NC cells form facial skeleton:
­ NC­derived mesenchyme condenses into nodules ­ some become osteoblasts – secrete collagen­proteoglycan osteoid matrix – binds calcium ­ osteocytes – osteoblasts that become embedded in the bony matrix ­ periosteum – membrane surrounding bones Osteoblasts Osteocytes Bone spicule – calcifiction Cardiac Neural Crest Cells The heart forms in the neck region, just below the pharyngeal arches Cardiac NC cells form the endothelial lining of the aortic arches ­ also forms the septum between the aorta and pulmonary artery; divides the truncus arteriosus
Cardiac Neural Crest Cranial midbrain forebrain hindbrain Vagal Cardiac Trunk Sacral
Cardiac neural crest cells develop into melanocytes, neurons, cartilage, or connective tissue of the 3 rd , 4 th , & 6 th pharyngeal arches