A missense mutation in Tbce causes progressive motor neuronopathy in mice.
Mice that are homozygous with respect to the progressive motor neuronopathy (pmn) mutation (chromosome 13) develop a progressive caudio-cranial degeneration of their motor axons from the age of two weeks and die four to six weeks after birth. The mutation is fully penetrant, and expressivity does not depend on the genetic background. Based on its pathological features, the pmn mutation has been considered an excellent model for the autosomal recessive proximal childhood form of spinal muscular atrophy (SMA). Previously, we demonstrated that the genes responsible for these disorders were not orthologous. Here, we identify the pmn mutation as resulting in a Trp524Gly substitution at the last residue of the tubulin-specific chaperone e (Tbce) protein that leads to decreased protein stability. Electron microscopy of the sciatic and phrenic nerves of affected mice showed a reduced number of microtubules, probably due to defective stabilization. Transgenic complementation with a wildtype Tbce cDNA restored a normal phenotype in mutant mice. Our observations indicate that Tbce is critical for the maintenance of microtubules in mouse motor axons, and suggest that altered function of tubulin cofactors might be implicated in human motor neuron diseases.
Martin
Natalia
N
Unité de Génétique des Mammifères, Institut Pasteur, 25 Rue du Docteur Roux, F-75724 Paris Cedex 15, France.
Jaubert
Jean
J
Gounon
Pierre
P
Salido
Eduardo
E
Haase
Georg
G
Szatanik
Marek
M
Guénet
Jean-Louis
JL
D000595:Amino Acid Sequence; D000818:Animals; D001369:Axons / Q000378:metabolism; D015152:Blotting, Northern; D019556:COS Cells; D002874:Chromosome Mapping; D003389:Cranial Nerve Diseases / Q000235:genetics*; D003433:Crosses, Genetic; D004252:DNA Mutational Analysis; D005822:Genetic Vectors; D006367:HeLa Cells; D006801:Humans; D017403:In Situ Hybridization; D051379:Mice; D008822:Mice, Transgenic; D008856:Microscopy, Fluorescence; D018832:Molecular Chaperones / Q000235:genetics* / Q000502:physiology; D008969:Molecular Sequence Data; D009154:Mutation; D020125:Mutation, Missense; D012333:RNA, Messenger / Q000378:metabolism; D013997:Time Factors; D014162:Transfection
D018832:Molecular Chaperones; D012333:RNA, Messenger; C469269:Tbce protein, mouse