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Preparation of Rat Oligodendrocyte Progenitor Cultures and Quantification of Oligodendrogenesis Using Dual-infrared Fluorescence Scanning
Published on: February 17, 2016
Differential and cell development-dependent localization of myelin mRNAs in oligodendrocytes
H de Vries1, J C de Jonge, C Schrage
1Department of Physiological Chemistry, Faculty of Medical Sciences, University of Groningen, The Netherlands.
Abstract:
In oligodendrocytes (OLG), the mRNAs for the various myelin proteins localize to different intracellular sites. Whereas the confinement of myelin basic protein (MBP) mRNA to the processes of the cell has been well established, we demonstrate that most other myelin mRNA species are mainly present in the perinuclear region. Using in situ hybridization of cultured rat OLG we found that mRNAs are localized to at least three different locations: 1) to the perinuclear region [myelin-associated glycoprotein (MAG) mRNA]; 2) mainly to the processes (the mRNA for the 14-kDa isoform of MBP); and 3) to both the perinuclear region and the primary processes [2',3'-cyclic nucleotide phosphodiesterase (CNPase) and proteolipid protein (PLP) mRNAs]. Thus, depending on their primary structure, the mRNA species in OLG either remain near the nucleus or localize to primary or secondary processes before their translation. The myelin mRNA localization correlates well with that of the proteins encoded in them, as demonstrated by immunocytochemistry. Since different isoforms of MBP have different locations in transfected HeLa cells (Staugaitis et al.: J Cell Biol 110:1719-1727, 1990), we also have investigated the localization of the various mRNAs in OLG, using exon 2-minus and exon 2-specific probes in situ hybridization. The exon 2-minus MBP mRNAs are transported far into the processes, whereas exon 2-specific mRNA was only detected in the cell body. This suggests that sorting and trafficking of MBP mRNA are regulated by the presence or absence of the exon 2 sequence. Furthermore, during maturation of OLG, exon 2-plus mRNAs disappear, whereas exon 2-minus mRNAs increase. The developmentally regulated expression of exon 2-plus transcripts suggest a role of their protein products in differentiation rather than in myelination.
Insights
Myelin mRNA localization in oligodendrocytes varies by protein. Myelin basic protein (MBP) mRNA is trafficked to processes, while other myelin mRNAs stay near the nucleus, impacting protein distribution.
Area of Science:
- Neuroscience
- Cell Biology
- Molecular Biology
Background:
- Oligodendrocytes (OLG) synthesize myelin proteins essential for nerve insulation.
- The intracellular localization of myelin protein mRNAs is crucial for their efficient translation and protein distribution.
Purpose of the Study:
- To investigate the intracellular localization patterns of various myelin protein mRNAs in cultured rat oligodendrocytes.
- To determine how mRNA localization correlates with protein localization and to explore the role of specific mRNA sequences in trafficking.
Main Methods:
- In situ hybridization was used to detect and localize specific myelin protein mRNAs (MBP, MAG, CNPase, PLP) in cultured rat oligodendrocytes.
- Immunocytochemistry was employed to confirm the localization of the corresponding proteins.
- Exon 2-specific and exon 2-minus probes were utilized to analyze the role of the exon 2 sequence in MBP mRNA trafficking.
Main Results:
- Different myelin mRNAs exhibit distinct localization patterns: MAG mRNA in the perinuclear region, 14-kDa MBP mRNA in processes, and CNPase/PLP mRNAs in both regions.
- mRNA localization generally correlated with the localization of their encoded proteins.
- Exon 2-minus MBP mRNA was found in processes, while exon 2-specific mRNA was confined to the cell body, indicating exon 2's role in MBP mRNA sorting.
- Exon 2-plus MBP mRNAs decreased, and exon 2-minus mRNAs increased during oligodendrocyte maturation.
Conclusions:
- Myelin mRNA localization in oligodendrocytes is diverse, with mRNAs either remaining near the nucleus or trafficking to cellular processes based on their sequence.
- The presence or absence of the exon 2 sequence in MBP mRNA regulates its sorting and trafficking.
- The developmental regulation of MBP mRNA isoforms suggests distinct roles for their protein products in oligodendrocyte differentiation versus myelination.
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