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Developmental changes of myelin-associated glycoprotein in rat brain: study on experimental hyperphenylalaninemia
Abstract:
We examined developmental changes of myelin-associated glycoprotein (MAG), basic protein (BP), and proteolipid protein (PLP) in central nervous system myelin isolated from experimental hyperphenylalaninemic rats (PKU rats) and controls. Higher amounts of MAG, including high-molecular-weight MAG in myelin, were found in 12- to 21-day-old control rats than in adult rats. MAG in developing myelin was at a maximum in 18-day-old rats and began to decrease in 21-day-old rats, while PLP and BP in developing myelin increased at these developmental stages. The level of high-molecular-weight MAG decreased in myelin prepared from 21-day-old rats. These results suggest that the decreasing high-molecular-weight MAG is important for compaction of myelin in the early stage of myelination. In myelin from 12- to 18-day-old PKU rats, the ratio of each protein such as MAG, PLP, or BP to that of control was about 0.5 at 12 days, and increased to almost 1.0 at 18 days. The myelination seems to be initially delayed but to be close to that of controls in PKU rats about 18 days old.
Insights
Phenylketonuria (PKU) in rats initially delays central nervous system myelination. However, myelination recovers by 18 days, suggesting high-molecular-weight myelin-associated glycoprotein (MAG) is crucial for early myelin compaction.
Area of Science:
- Neuroscience
- Developmental Biology
- Biochemistry
Background:
- Myelin proteins, including myelin-associated glycoprotein (MAG), basic protein (BP), and proteolipid protein (PLP), are crucial for central nervous system (CNS) development.
- Hyperphenylalaninemia, as seen in phenylketonuria (PKU), can impact neurological development.
Purpose of the Study:
- To investigate the developmental changes of MAG, BP, and PLP in the CNS myelin of experimental hyperphenylalaninemic rats (PKU rats) compared to controls.
- To understand the role of high-molecular-weight MAG in the early stages of myelination.
Main Methods:
- Isolation and analysis of CNS myelin from control and PKU rats at various developmental stages (12, 18, and 21 days old).
- Quantification of MAG, BP, and PLP levels, including high-molecular-weight MAG, in isolated myelin.
Main Results:
- In control rats, MAG levels peaked around 18 days and decreased by 21 days, while PLP and BP levels increased.
- High-molecular-weight MAG decreased in myelin from 21-day-old control rats, suggesting its importance for myelin compaction.
- PKU rats showed delayed myelination initially, with protein ratios relative to controls around 0.5 at 12 days, increasing to nearly 1.0 by 18 days.
Conclusions:
- Decreasing high-molecular-weight MAG is likely essential for myelin compaction during early myelination.
- Myelination in PKU rats appears to be initially delayed but approaches control levels by approximately 18 days of age.