## Abstract Duplication of __PLP1__, an X‐linked gene encoding the major myelin membrane protein of the human CNS, is the most frequent cause of Pelizaeus‐Merzbacher disease (PMD). Transgenic mice with extra copies of the wild type __Plp1__ gene, a valid model of PMD, also develop a dysmyelinating
PLP/DM20 Expression and turnover in a transgenic mouse model of pelizaeus-merzbacher disease
✍ Scribed by Saadia A. Karim; Jennifer A. Barrie; Mailis C. Mcculloch; Paul Montague; Julia M. Edgar; Debrah L. Iden; Thomas J. Anderson; Klaus-Armin Nave; Ian R. Griffiths; Mark McLaughlin
- Publisher
- John Wiley and Sons
- Year
- 2010
- Tongue
- English
- Weight
- 950 KB
- Volume
- 58
- Category
- Article
- ISSN
- 0894-1491
No coin nor oath required. For personal study only.
✦ Synopsis
Abstract
The most common cause of Pelizaeus‐Merzbacher (PMD) is due to duplication of the PLP1 gene but it is unclear how increased gene dosage affects PLP turnover and causes dysmyelination. We have studied the dynamics of PLP/DM20 in a transgenic mouse model of PMD with increased gene dosage of the proteolipid protein gene (Plp1). The turnover of PLP/DM20 were investigated using an ex‐vivo brain slice system and cultured oligodendrocytes. Homozygous mice have reduced PLP translation, markedly enhanced PLP degradation, and markedly reduced incorporation of PLP into myelin. Proteasome inhibition (MG132) prevented the enhanced degradation. Numerous autophagic vesicles are present in homozygous transgenic mice that may influence protein dynamics. Surprisingly, promoting autophagy with rapamycin decreases the degradation of nascent PLP suggesting autophagic vacuoles serve as a cellular storage compartment. We suggest that there are multiple subcellular fates of PLP/DM20 when overexpressed: the vast majority being degraded by the proteasome, a proportion sequestered into autophagic vacuoles, probably fused with endolysosomes, and only a small proportion entering the myelin sheath, where its association with lipid rafts is perturbed. Transgenic oligodendrocytes have fewer membrane sheets and this phenotype is improved with siRNA‐mediated knockdown of PLP expression that promotes the formation of MBP+ myelin‐like sheets. This finding suggests that RNAi technology is in principle applicable to improve CNS myelination when compromised by PLP/DM20 overexpression. © 2010 Wiley‐Liss, Inc.
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