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The Fragile X Syndrome – Where Do We Go?

Review ARTICLE Provisionally accepted The full-text will be published soon. Notify me

Front. Mol. Neurosci. | doi: 10.3389/fnmol.2019.00135

Structural and Functional Abnormalities in the Olfactory System of Fragile X Syndrome Models

  • 1Laboratory of Cellular and Neuronal Dynamics, University of Chile, Chile
  • 2Geroscience Center for Health and Brain Metabolism (GERO), Chile
  • 3Biomedical Research Center, Autonomous University of Chile, Chile
  • 4Center for Biomedical and Applied Research, Faculty of Medical Sciences, University of Santiago, Chile, Chile
  • 5Buck Institute for Research on Aging, United States
  • 6Laboratory of Physiology, Department of Biology, Faculty of Science, University of Chile, Chile
  • 7Universidad de Chile, Chile

Fragile Syndrome X (FXS) is the most common inherited form of intellectual disability. It is produced by mutation of the Fmr1 gene that encodes for the Fragile Mental Retardation Protein (FMRP), an important RNA-binding protein that regulates the expression of multiple proteins located in neuronal synapses. Individuals with FXS exhibit abnormal sensory information processing frequently leading to hypersensitivity across sensory modalities and consequently a wide array of behavioral symptoms. Insects and mammals engage primarily their sense of smell to create proper representations of the external world and guide adequate decision-making processes. This feature in combination with the exquisitely organized neuronal circuits found throughout the olfactory system and the wide expression of FMRP in brain regions that process olfactory information makes it an ideal model to study sensory alterations in FXS models. In the last decade several groups have taken advantage of these features and have used the olfactory system of fruit fly and rodents to understand neuronal alteration giving rise to sensory perception issues. In this review we will discuss molecular, morphological and physiological aspects of the olfactory information processing in FXS models. We will highlight the decreased inhibitory/excitatory synaptic balance and the diminished synaptic plasticity found in this system resulting in behavioral alteration of individuals in the presence of odorant stimuli.

Keywords: Olfactory coding, olfactory behavior, Fmr1-KO mouse, FMRP, dfmr1, structural plasticity, excitation/ inhibition balance

Received: 14 Jan 2019; Accepted: 09 May 2019.

Edited by:

Teresa Duda, Salus University, United States

Reviewed by:

Claudia Bagni, Département des Neurosciences Fondamentales, Faculté de Biologie et de Médecine, Université de Lausanne, Switzerland
Thomas O. Maurin, Centre National de la Recherche Scientifique (CNRS), France  

Copyright: © 2019 Bodaleo, Tapia-Monsalves, Cea-Del Rio, Gonzalez-Billault and Nunez-Parra. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence: Dr. Alexia Nunez-Parra, Laboratory of Physiology, Department of Biology, Faculty of Science, University of Chile, Santiago, Chile,