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Oligodendrocyte development and differentiation in the rumpshaker mutation
M L Fanarraga1, I U Sommer, I R Griffiths
1Department of Veterinary Surgery, University of Glasgow, Scotland.
Abstract:
The jimpy rumpshaker (jprsh) mutation is an amino acid substitution in exon 4 (Ile186-->Thr) of the proteolipid protein (PLP) gene on the X chromosome. Affected mice show moderate hypomyelination of the central nervous system (CNS) with increased numbers of oligodendrocytes in the white matter of the spinal cord, a feature distinguishing them from other PLP mutations such as jp, in which premature cell death occurs with reduced numbers of oligodendrocytes. Myelin sheaths of jprsh immunostain for myelin basic protein (MBP) and DM-20, but very few contain PLP. This study examines the differentiation of oligodendrocytes cultured from the spinal cords of young mutant and wild type mice using various surface and cytoplasmic antigenic markers to define the stage of development. The majority of oligodendrocytes from mutant mice progress normally to express MBP; approximately 30%, relative to wild type, contain DM-20 at the in vivo age of 16 days, but very few immunostain for PLP or the O10 and O11 markers. The morphology of mutant cells in respect to membrane sheets and processes appears similar to normal. The jprsh oligodendrocyte is, therefore, characterized by a failure to express the markers indicative of the most mature cell; however, it is probably able to achieve a normal period of survival. These data, taken in conjunction with previous results, suggest that the PLP gene has at least two functions; one, probably involving PLP, is concerned with a structural role in normal myelin compaction; the other, perhaps related to DM-20 (or another lower molecular weight proteolipid), is essential for cell survival. The mutation in jprsh at residue 186 suggests that this region, which is common to PLP and DM-20, is not critical for this latter function.
Insights
The jimpy rumpshaker (jprsh) mutation in mice causes hypomyelination by affecting proteolipid protein (PLP) expression. Mutant oligodendrocytes fail to mature but likely survive, suggesting PLP has distinct roles in myelin structure and cell survival.
Area of Science:
- Neuroscience
- Genetics
- Cell Biology
Background:
- The jimpy rumpshaker (jprsh) mutation involves an amino acid substitution in the proteolipid protein (PLP) gene.
- Affected mice exhibit central nervous system (CNS) hypomyelination with increased oligodendrocytes, differing from other PLP mutations.
Purpose of the Study:
- To analyze oligodendrocyte differentiation in jprsh mutant mice using antigenic markers.
- To understand the functional impact of the jprsh mutation on myelin development and oligodendrocyte maturation.
Main Methods:
- Culturing oligodendrocytes from spinal cords of mutant and wild-type mice.
- Immunostaining for myelin basic protein (MBP), DM-20, PLP, and specific cell surface markers (O10, O11).
Main Results:
- Oligodendrocytes from jprsh mice express MBP but show reduced DM-20 expression and minimal PLP, O10, or O11 staining.
- Mutant oligodendrocytes exhibit normal morphology and likely normal survival despite failing to express mature cell markers.
- The jprsh mutation affects PLP expression critical for myelin compaction but not cell survival.
Conclusions:
- The PLP gene likely has dual functions: structural role in myelin compaction (via PLP) and essential role in cell survival (potentially via DM-20).
- The jprsh mutation at residue 186 highlights that this region is not critical for the cell survival function of PLP-related proteins.