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Free Content Embryogenesis of the Olfactory System: Part I: Embryogenesis of the Olfactory Nasal Mucosa and the Olfactory Bulb

Olfaction is the oldest of human senses. It is the only sense in which sensory neurons project outside the calvaria to detect sensory signals. It is the only sense that transmits information directly to the oldest portion of the human brain (the paleocortex) without any intervening thalamic relay. It is the single sense generated and supported by the largest family of genes. The olfactory system develops as a coordinated interaction between the ingrowth of olfactory sensory neurons from the olfactory epithelium of the nose and the outgrowth of the olfactory diverticulum from the frontal lobe. It is supported by continual, lifelong replenishment of the system by olfactory progenitor neurons of the nose and progenitor interneurons from the subventricular zone of the brain.

Learning Objective: To understand more completely the development of the “peripheral” portion of the olfactory system.

Keywords: ACTIVINβB = protein complex involved in cell proliferation and differentiation; BMP = bone morphogenetic protein (BMP 2,4,7); CADHERIN = calcium-dependent adhesion proteins are a class of type 1 transmembrane proteins (they play roles in cell adhesion, and they are calcium ion dependent); COUP-TF1 = chicken ovalbumin upstream promotor transcription factor 1 (a nuclear hormone receptor); EGF = epidermal growth factor; EMX2 = homolog of the Drosophila empty spiracles gene (it is a transcription factor that helps pattern the brain); FGF = fibroblast growth factor(s) (FGF8 is one of these factors); GDF-11 = growth differentiation factor 11; HGF = hepatocyte growth factor; IGF-I = insulin growth factor I; LIF = leukemia inhibitory factor; NO = nitric oxide; Neuropilin = neuropilins are multifunctional non‐tyrosine kinase receptors that play a key role in mediating axonal guidance in the developing nervous system; OCT1 = octamer transcription factor, a stress sensor; ORN = olfactory receptor neuron; PAX = a group of paired box gene transcription factors, including PAX 6 and 7; RA = retinoic acid; SEMA3A = semaphorin 3a, whose proteins can be chemoattractive or chemorepulsive to apical dendrites; SHH = sonic hedgehog protein; SLIT1, SLIT2 = Slit homolog 1 and 2 genes, guidance molecules; SOX2 = sex-determined region Y-box is a neural-inducing homeobox gene; TENASCIN-C = a glycoprotein that is expressed in the extracellular matrix; it plays a role in restricting neurogenic areas of the central nervous system; WNT = gene family that presently consists of 19 genes that make ligands that are signaling molecules prominent in many areas of embryogenesis (WNT 1‐19); cAMP = cyclic adenosine monophosphate; iNOS = nitric oxide synthase

Document Type: Research Article

Publication date: February 1, 2018

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