Programmed cell death in the dysmyelinating mutants
1Department of Anatomy and Cell Biology, Wayne State University School of Medicine, Detroit, MI 48201, USA.
Abstract:
A large number of genetic mutants that are missing a particular myelin protein or that have an aberrant myelin protein composition have been described. These mutations usually cause dysmyelination in the PNS or CNS. Similarly, the nervous system of animals experimentally altered to block synthesis of myelin proteins have recently been generated that show aberrations in the myelin sheath. For both groups of animals, the numbers of myelinating cells remain relatively stable and glial cell death is minimal. The exception is animals with mutations in the proteolipid protein (PLP) gene which exhibit extensive death of oligodendrocytes (OLs). The degree of OL death in the PLP mutants generally correlates with the amount of dysmyelination. Dying OLs in the PLP mutants exhibit the classical features of apoptotic cells. Programmed cell death (PCD) is often, but not necessarily, manifested by cleavage of DNA into abundant oligonucleosomal fragments. Detection of these abundant DNA fragments was examined in normal and jimpy (jp) mice using the TUNEL (terminal deoxynucleotidyl transferase dUTP nick end labeling) method. In normal spinal cord and brain, at least twice as many cells exhibited DNA fragmentation when compared to numbers of pyknotic glia observed microscopically. In jp spinal cord and brain, roughly one-half of cells exhibited DNA fragmentation when compared to numbers of pyknotic glia observed microscopically. PCD of cells in normal development involving DNA fragmentation has been previously described and our results support that conclusion.(ABSTRACT TRUNCATED AT 250 WORDS)
Insights
Genetic mutations affecting myelin proteins can cause central nervous system (CNS) dysmyelination. Proteolipid protein (PLP) gene mutations specifically trigger significant oligodendrocyte (OL) death via apoptosis, confirmed by DNA fragmentation analysis.
Area of Science:
- Neuroscience
- Cell Biology
- Genetics
Background:
- Myelin proteins are crucial for nervous system integrity.
- Mutations in myelin protein genes often lead to dysmyelination in the peripheral (PNS) and central nervous systems (CNS).
- Oligodendrocyte (OL) survival is generally maintained in myelin mutants, except for those affecting proteolipid protein (PLP).
Purpose of the Study:
- To investigate the mechanism of oligodendrocyte death in proteolipid protein (PLP) mutants.
- To determine if programmed cell death (PCD) is involved in OL loss in PLP mutants.
- To quantify DNA fragmentation as an indicator of PCD in normal and mutant mice.
Main Methods:
- Analysis of genetic mutants with aberrant myelin protein composition.
- Microscopic examination of glial cell death and numbers.
- TUNEL (terminal deoxynucleotidyl transferase dUTP nick end labeling) assay to detect DNA fragmentation in normal and jimpy (jp) mice.
- Comparison of DNA fragmentation levels with pyknotic glia counts.
Main Results:
- PLP gene mutations lead to extensive oligodendrocyte (OL) death, correlating with the degree of dysmyelination.
- Dying OLs in PLP mutants display classical apoptotic features.
- TUNEL assay revealed significant DNA fragmentation in both normal and jp mice, with specific quantitative differences observed.
Conclusions:
- Programmed cell death (PCD), indicated by DNA fragmentation, is a key feature of OL loss in PLP mutants.
- The study supports the role of PCD in nervous system development and myelin disorders.
- Quantitative analysis of DNA fragmentation provides insights into the extent of cell death in myelin-related neuropathies.
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