Different intracellular pathomechanisms produce diverse Myelin Protein Zero neuropathies in transgenic mice.
Missense mutations in 22 genes account for one-quarter of Charcot-Marie-Tooth (CMT) hereditary neuropathies. Myelin Protein Zero (MPZ, P0) mutations produce phenotypes ranging from adult demyelinating (CMT1B) to early onset [Déjérine-Sottas syndrome (DSS) or congenital hypomyelination] to predominantly axonal neuropathy, suggesting gain of function mechanisms. To test this directly, we produced mice in which either the MpzS63C (DSS) or MpzS63del (CMT1B) transgene was inserted randomly, so that the endogenous Mpz alleles could compensate for any loss of mutant P0 function. We show that either mutant allele produces demyelinating neuropathy that mimics the corresponding human disease. However, P0S63C creates a packing defect in the myelin sheath, whereas P0S63del does not arrive to the myelin sheath and is instead retained in the endoplasmic reticulum, where it elicits an unfolded protein response (UPR). This is the first evidence for UPR in association with neuropathy and provides a model to determine whether and how mutant proteins can provoke demyelination from outside of myelin.
DIBIT, San Raffaele Scientific Institute, 20132 Milan, Italy. l.wrabetz@hsr.it
Lawrence
L
Wrabetz
Maurizio
M
D'Antonio
Maria
M
Pennuto
Gabriele
G
Dati
Elisa
E
Tinelli
Pietro
P
Fratta
Stefano
S
Previtali
Daniele
D
Imperiale
Jurgen
J
Zielasek
Klaus
K
Toyka
Robin L
RL
Avila
Daniel A
DA
Kirschner
Albee
A
Messing
M Laura
ML
Feltri
Angelo
A
Quattrini
D000818:Animals; D002607:Charcot-Marie-Tooth Disease / Q000235:genetics* / Q000378:metabolism* / Q000473:pathology; D004195:Disease Models, Animal; D051379:Mice; D008822:Mice, Transgenic; D016297:Mutagenesis, Site-Directed; D018993:Myelin P0 Protein / Q000235:genetics* / Q000378:metabolism*; D009413:Nerve Fibers, Myelinated / Q000378:metabolism* / Q000473:pathology
D018993:Myelin P0 Protein