Journal Article

Mutant HSPB8 causes motor neuron-specific neurite degeneration

Joy Irobi, Leonardo Almeida-Souza, Bob Asselbergh, Vicky De Winter, Sofie Goethals, Ines Dierick, Jyothsna Krishnan, Jean-Pierre Timmermans, Wim Robberecht, Peter De Jonghe, Ludo Van Den Bosch, Sophie Janssens and Vincent Timmerman

in Human Molecular Genetics

Volume 19, issue 16, pages 3254-3265
Published in print August 2010 | ISSN: 0964-6906
Published online June 2010 | e-ISSN: 1460-2083 | DOI: http://dx.doi.org/10.1093/hmg/ddq234

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Missense mutations (K141N and K141E) in the α-crystallin domain of the small heat shock protein HSPB8 (HSP22) cause distal hereditary motor neuropathy (distal HMN) or Charcot-Marie-Tooth neuropathy type 2L (CMT2L). The mechanism through which mutant HSPB8 leads to a specific motor neuron disease phenotype is currently unknown. To address this question, we compared the effect of mutant HSPB8 in primary neuronal and glial cell cultures. In motor neurons, expression of both HSPB8 K141N and K141E mutations clearly resulted in neurite degeneration, as manifested by a reduction in number of neurites per cell, as well as in a reduction in average length of the neurites. Furthermore, expression of the K141E (and to a lesser extent, K141N) mutation also induced spheroids in the neurites. We did not detect any signs of apoptosis in motor neurons, showing that mutant HSPB8 resulted in neurite degeneration without inducing neuronal death. While overt in motor neurons, these phenotypes were only very mildly present in sensory neurons and completely absent in cortical neurons. Also glial cells did not show an altered phenotype upon expression of mutant HSPB8. These findings show that despite the ubiquitous presence of HSPB8, only motor neurons appear to be affected by the K141N and K141E mutations which explain the predominant motor neuron phenotype in distal HMN and CMT2L.

Journal Article.  6954 words.  Illustrated.

Subjects: Genetics and Genomics

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