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Defects in specific associations between astroglia and neurons occur in microcultures of weaver mouse cerebellar
Abstract:
The neurological mutation weaver is characterized by defects in granule cell migration along Bergmann glial processes and by subsequent death and disposition of granule cells. Immunocytochemical localization of antisera raised against purified glial filament protein (AbGF) and transmission electron microscopy were used to visualize specific associations between granule neurons and astroglia in microcultures of cerebellar cells dissociated from normal (+/+), heterozygous (+/wv), and homozygous (wv/wv) B6CBA-w mouse cerebella. In microcultures of cells dissociated from normal B6CBA-Aw-J-wv (+/+) cerebella, staining with AbGF closely resembled results previously reported for cells taken from C57BL/6J (+/+) tissue. Two forms of stained astroglia were seen, one with a larger perikaryon and shorter processes, among which 12 to 20 unstained cells nestled; and another with a smaller cell soma and longer processes, along which a few unstained cells were seen. The first resembled astrocytes of the internal granular layer and white matter, the second Bergmann astroglia. In microcultures of heterozygous animals (+/wv), the number of granule cells was reduced slightly. Many stained astroglia resembled those from +/+ cerebella, but others had thickened processes and enlarged terminal "endfeet." Granule cells associated with both forms of stained astroglia. Cultures from homozygous weaver (wv/wv) cerebella contained very few, if any, granule cells and did not exhibit specific neuronal/glial interactions characteristic of +/+ cells. Both forms of stained wv/wv glial cells had enlarged cell somata giving rise to stunted processes, suggesting that both Bergmann glia and astrocytes are affected by the weaver gene. By both immunocytochemical staining and electron microscopy, accumulation and tangling of glial filaments were seen. Immunocytochemical staining of weaver cerebellar tissue with AbGF also revealed abnormalities in astrocytes of the internal granular layer and white matter in addition to previously reported defects in Bergmann glia. Agglutination with five plant lectins, each with a different carbohydrate-binding specificity, revealed that postnatal weaver cerebellar cells agglutinate with the lectins concanavalin A and the wheat germ agglutinin, suggesting the persistence postnatally of embryonic cell surface elements on postnatal weaver cells.
Insights
The weaver neurological mutation in mice causes cerebellar granule cell defects and glial abnormalities. This study reveals widespread glial pathology and altered cell surface properties in weaver mice.
Area of Science:
- Neuroscience
- Developmental Biology
- Cell Biology
Background:
- The weaver mutation in mice disrupts cerebellar granule cell migration and survival.
- Glial cells, particularly Bergmann glia, are implicated in guiding granule cell development.
- Understanding the cellular basis of weaver mutation is crucial for insights into cerebellar development and neurological disorders.
Purpose of the Study:
- To investigate the cellular and ultrastructural defects in cerebellar neurons and glia caused by the weaver mutation.
- To characterize the specific glial cell types affected by the weaver gene.
- To examine alterations in cell surface components of weaver mutant cerebellar cells.
Main Methods:
- Immunocytochemical localization of glial filament protein (AbGF) in microcultures of cerebellar cells from normal, heterozygous, and homozygous weaver mice.
- Transmission electron microscopy (TEM) to visualize neuronal-glial interactions and glial ultrastructure.
- Plant lectin agglutination assays to assess cell surface carbohydrate expression.
Main Results:
- Homozygous weaver (wv/wv) cerebellar cultures showed a severe reduction in granule cells and abnormal glial morphology, including enlarged somata and stunted processes.
- Both Bergmann glia and astrocytes exhibited abnormalities, with accumulation and tangling of glial filaments observed.
- Heterozygous (+/wv) mice displayed mild granule cell reduction and some glial alterations, including thickened processes and enlarged endfeet.
- Weaver cerebellar cells showed altered cell surface properties, agglutinating with specific plant lectins (concanavalin A and wheat germ agglutinin).
Conclusions:
- The weaver gene affects multiple glial cell types in the cerebellum, not just Bergmann glia.
- Glial filament accumulation and abnormal glial morphology are key pathological features of the weaver mutation.
- Altered cell surface characteristics in weaver mutant cells suggest a potential role in developmental defects.