BIOL 370 – Developmental Biology Topic #13 Neural Crest Cells and Axonal Specificity Lange In this chapter, we continue to look at more advanced development of the ectoderm. The foci we shall have in this chapter, however, will examine how the ectoderm will be further developed specifically in the • NEURAL CREST CELLS • AXONAL SPECIFICITY Within each of the above, we will specifically examine: • Formation of the facial skeleton, pigment cells, and the peripheral nervous system using neural crest cells • Formation of axonal growth cones The key underlying concept with this chapter is to recognize how progression in development of the neural crest cells and the axonal growth cones both require the cells to significantly migrate for successful development. We shall be examining some of the chemical signals that help guide these processes. Figure 10.1 Neural crest cell migration (Part 2) NOTICE THE SMALL SIZE OF THE NEURAL CREST CELLS Experiment 1 & 2 are the same experiment in two different trials. flourscent dextran was injected into the neural crest cells and their movement during development followed. Figure 10.2 Model for neural crest lineage segregation and the heterogeneity of neural crest cells Four types of cells are in the neural crest zone (all are committed cells, but are progenitors): • • • • C = cartilage/bone G = glia N = neurons M = melanocytes Figure 10.4 Regions of the chick neural crest • Cranial portion of neural crest bones & cartilage of face and neck, cranial nerves • Cardiac portion of neural crest differentiates and divides pulmonary arteries and aorta • Vagal & Sacral portions of neural crest form parasympathetic nervous system of the digestive system • Trunk portions of the neural crest sympathetic neurons, melanocytes, and adrenal medula. Cranial portion of neural crest bones & cartilage of face and neck, cranial nerves Figure 10.12 During craniofacial development, mesencephalic cranial neural crest cells migrate to become the mesenchyme of the future face and much of the skull Figure 10.17 The influence of mesoderm and ectoderm on the axial identity of cranial neural crest cells and the role of Hoxa2 in regulating second-arch morphogenesis Cardiac portion of neural crest differentiates and divides pulmonary arteries and aorta Figure 10.15 The septum that separates the truncus arteriosus into the pulmonary artery and the aorta forms from cells of the cardiac neural crest The appearance of the “normal” human heart in section. Ventral Septal Defect - the most common congenital cardiac anomalies. • Found in 30-60% of all newborns with a congenital heart defect • This equates to about 2-6 per 1000 births. • During heart formation, when the heart begins as a hollow tube, it begins to partition, forming septa. Patent Ductus Arteriosus Prior to parturition, a blood vessel called the ductus arteriosus connects the pulmonary artery — the artery carrying blood to your lungs — and the aorta, the large artery that carries blood away from the heart. In mammals, prior to parturition, the ductus arteriosus allows blood to bypass the lungs because the embryo receives oxygen through the placenta and umbilical cord. Transposition of the Great Arteries With this defect, the positions of the and the pulmonary artery, are reversed (transposed). Due to this transposition of the great arteries, the aorta arises from the right ventricle instead of the left ventricle and the pulmonary artery arises from the left ventricle instead of the right. This prevents nourishing oxygenated blood from reaching the body. Vagal & Sacral portions of neural crest form parasympathetic nervous system of the digestive system Parasympathetic Sympathetic Eye Brain stem Salivary glands Heart Eye Skin* Cranial Sympathetic ganglia Salivary glands Cervical Lungs Lungs T1 Heart Stomach Thoracic Stomach Pancreas Pancreas Liver and gallbladder L1 Liver and gallbladder Adrenal gland Lumbar Bladder Bladder Genitals Genitals Human Anatomy and Physiology, 7e by Elaine Marieb & Katja Hoehn Sacral Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings. Trunk portions of the neural crest sympathetic neurons, melanocytes, and adrenal medula Figure 10.5 Neural crest cell migration in the trunk of the chick embryo Neural crest cell movement shown in the dark, teal blue layers. Figure 10.6 All migrating neural crest cells are stained red by antibody to HNK-1 (Also, see Lipinski et. al., 1983) Figure 10.8 Entry of neural crest cells into the gut and adrenal gland In “A” the fluorescence is highlighting enteric ganglia that control peristaltic movement In “B” the solid circle represents the adrenal medulla, the green fluorescence Two different stainings are seen in “A”. The neural crest cells are migrating into the adrenal as seen by the red stained cells for Sox8. The green stain (SF1) identifies adrenal cortex cells. Figure 10.9 Neural crest cell migration in the dorsolateral pathway through the skin In this mouse image (A), the purple is staining melanoblasts. In the chick (B), the arrows point to melanoblasts Melanoblasts will of course create melanocytes. Figure 10.10 Cranial neural crest cell migration in the mammalian head (Part 1) Pharyngeal Arches are early regions that develop into a multitude of structures. Figure 10.10 Cranial neural crest cell migration in the mammalian head (Part 3) Figure 10.11 Intramembranous ossification Below, we see the chick head as bone formation (ossification of cartilage) occurs. Figure 10.28 The trigeminal ganglion has three main branches Trigeminal Ganglia branches into: • Ophthalmic nerve • Maxillary nerve • Mandibular nerve Bone Morphogenetic Protein 4 The growth of these nerve branches is governed by the BMP4 gene. Figure 10.29 Embryonic axon from a rat dorsal root ganglion turning in response to a source of NT3 Neurotrophin 3 NT3 is a neurotrophic factor in the nerve growth factor family (NGF) family of neurotrophins. It is a protein growth factor which has activity on certain neurons in the nervous system In the images, we see how NT3 added to the region near rat dorsal root ganglion causes turning of the growing axon cones towards the chemical. Figure 10.30 Differentiation of a motor neuron synapse with a muscle in mammals An example of growth cones being used to differentiate a neuromuscular junction. Figure 10.31 Effects of NGF and BDNF on axonal outgrowths Nerve Growth Factor (NGF) and Brain-Derived Neurotrophic Factor (BDNF) are both neurotropins, but their effects are specialized. NGF effect pronounced BDNF effect minimal NGF effect pronounced BDNF effect pronounced NGF effect minimal BDNF effect pronounced Figure 10.32 Making a “brainbow” • A brainbow is a construct in which neuroanatomists can process and define individual neurons in the brain from neighboring neurons using a wide hue of fluorescent proteins. • Random expression of different ratios of red, green, and blue derivatives, it is possible to flag each neuron with a distinctive color. • This process has been a major contribution to the field of connectomics, or the study of neural connections in the brain. • The study of neural pathways is also known as hodology by earlier neuroanatomists. Jeff W. Lichtman Joshua R. Sanes The technique behind creating a “brainbow” was originally developed in the Spring of 2007 by a team led by Jeff W. Lichtman and Joshua R. Sanes. End.