Related Experiment Videos
The pH of jimpy glia is increased: intracellular measurements using fluorescent laser cytometry
Abstract:
The jimpy mutation lies in the gene which codes for myelin proteolipid protein, and the brains and spinal cords of jimpy mice contain little myelin and no measurable proteolipid protein. It has been thought that the mutation affected only the myelin forming oligodendroglial cells, but there is now considerable evidence that astroglia are also a target of the mutation since jimpy astrocytes exhibit a prominent gliosis along with defects in metabolism and proliferation. Because cell proliferation is associated with an increase in intracellular pH, we investigated whether the pH of jimpy glia was abnormal. Using a pH sensitive fluorescent dye and a laser cytometry system we measured the intracellular pH of individual cells in cultures derived from both jimpy and normal brains. The relative pH of flat astrocytes in jimpy cultures was higher than in normal cultures by an average of 0.24 pH units, and these increased values were evident 2-3 days after plating. At this in vitro age the cultures contain only a few oligodendrocytes, none of which express detectable proteolipid protein. The pH of the process-bearing cell population, which contains the oligodendrocytes as well as some astrocytes and presumptive glial precursors, was also increased but not until 7 days in culture. The finding that a mutation in the myelin proteolipid protein gene can alter the normal pH of astrocytes is quite unexpected since, as far as is known, astrocytes do not make proteolipid protein. These results and others discussed in this paper support the hypothesis that either proteolipid protein itself, or some other product of the gene, may have an important role in central nervous system development.
Insights
The jimpy mutation, affecting myelin proteolipid protein, causes abnormal intracellular pH in astrocytes and other glial cells in mice. This unexpected finding suggests a broader role for proteolipid protein in central nervous system development.
Area of Science:
- Neuroscience
- Cell Biology
- Genetics
Background:
- The jimpy mutation is linked to the myelin proteolipid protein (PLP) gene, resulting in reduced myelin and PLP in the central nervous system.
- While initially thought to affect only oligodendrocytes, evidence suggests jimpy astrocytes also display gliosis and defects in metabolism and proliferation.
Purpose of the Study:
- To investigate the intracellular pH of glial cells in jimpy mice, given the association between cell proliferation and increased pH.
- To determine if the jimpy mutation impacts astrocyte and oligodendrocyte pH.
Main Methods:
- Utilized a pH-sensitive fluorescent dye and laser cytometry to measure intracellular pH in cultured brain cells from jimpy and normal mice.
- Analyzed pH levels in both flat astrocytes and process-bearing cell populations at different time points post-plating.
Main Results:
- Jimpy astrocytes exhibited a significantly higher average intracellular pH (0.24 units) compared to normal astrocytes, evident within 2-3 days of culture.
- The process-bearing cell population, including oligodendrocytes and astrocytes, showed increased pH at 7 days in culture.
- These pH alterations occurred in cells not known to express proteolipid protein.
Conclusions:
- The jimpy mutation, affecting myelin proteolipid protein, unexpectedly alters astrocyte intracellular pH.
- These findings challenge the understanding of PLP function and suggest a potential role beyond myelin formation in central nervous system development.