title: Olfactory system and demyelination.
abstract: Within the central nervous system, the olfactory system represents one of the most exciting scenarios since it presents relevant examples of long-life sustained neurogenesis and continuous axonal outgrowth from the olfactory epithelium with the subsequent plasticity phenomena in the olfactory bulb. The olfactory nerve is composed of nonmyelinated axons with interesting ontogenetic interpretations. However, the centripetal projections from the olfactory bulb are myelinated axons which project to more caudal areas along the lateral olfactory tract. In consequence, demyelination has not been considered as a possible cause of the olfactory symptoms in those diseases in which this sense is impaired. One prototypical example of an olfactory disease is Kallmann syndrome, in which different mutations give rise to combined anosmia and hypogonadotropic hypogonadism, together with different satellite symptoms. Anosmin-1 is the extracellular matrix glycoprotein altered in the X-linked form of this disease, which participates in cell adhesion and migration, and axonal outgrowth in the olfactory system and in other regions of the central nervous system. Recently, we have described a new patho-physiological role of this protein in the absence of spontaneous remyelination in multiple sclerosis. In the present review, we hypothesize about how both main and satellite neurological symptoms of Kallmann syndrome may be explained by alterations in the myelination. We revisit the relationship between the olfactory system and myelin highlighting that minor histological changes should not be forgotten as putative causes of olfactory malfunction.
authors.affiliation: Grupo de Neurobiología del Desarrollo-GNDe, Hospital Nacional de Parapléjicos-SESCAM, Toledo, Spain.
authors.forename: D
authors.initials: D
authors.lastname: Garcia-Gonzalez
authors.forename: V
authors.initials: V
authors.lastname: Murcia-Belmonte
authors.forename: D
authors.initials: D
authors.lastname: Clemente
authors.forename: F
authors.initials: F
authors.lastname: De Castro
mesh_terms: D000818:Animals; D003711:Demyelinating Diseases / Q000235:genetics / Q000378:metabolism* / Q000473:pathology / Q000503:physiopathology; D016326:Extracellular Matrix Proteins / Q000235:genetics; D020022:Genetic Predisposition to Disease; D006801:Humans; D017436:Kallmann Syndrome / Q000235:genetics / Q000378:metabolism* / Q000473:pathology / Q000503:physiopathology; D009154:Mutation; D009186:Myelin Sheath / Q000378:metabolism* / Q000473:pathology; D009419:Nerve Tissue Proteins / Q000235:genetics; D000857:Olfaction Disorders / Q000235:genetics / Q000378:metabolism* / Q000473:pathology / Q000503:physiopathology; D009833:Olfactory Pathways / Q000378:metabolism* / Q000473:pathology / Q000503:physiopathology; D055696:Olfactory Perception / Q000235:genetics; D010641:Phenotype; D015398:Signal Transduction; D012903:Smell / Q000235:genetics
chemical_list: C076266:ANOS1 protein, human; D016326:Extracellular Matrix Proteins; D009419:Nerve Tissue Proteins
keywords: FGF2; FGFR1; Kallmann Syndrome; anosmin-1; lateral olfactory tract; multiple sclerosis; myelin; olfactory bulb; subventricular zone