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Expression of various microtubule-associated protein 2 forms in the developing mouse brain and in cultured neurons
C Charrière-Bertrand1, C Garner, M Tardy
1INSERM U. 282-CNRS, Hôpital Henri Mondor, Créteil, France.
Abstract:
A cDNA probe specific to microtubule-associated protein 2 (MAP2) was used to study the expression of the mRNAs encoding the high- and low-molecular-weight MAP2 variants in cultured neurons and astrocytes. The timing and relative abundance of these MAP2 transcripts and of their encoded proteins were also studied in the developing cerebral hemispheres and cerebellum of the mouse. A 9-kb mRNA, known to encode high-molecular-weight MAP2, was expressed in cultured astrocytes, albeit at a lower level than in neurons. The 6-kb transcript, recently shown to encode low-molecular-weight MAP2 (MAP2c), was expressed in neurons and was the predominant MAP2 transcript of the astrocytes. The level of the 9- and 6-kb transcripts decreased at late stages of astroglial and neuronal cell culture. The 9-kb mRNA was detected in the cerebellum and cerebral hemispheres at every developmental stage. Although the levels of this mRNA varied slightly in the cerebral hemispheres, its expression was biphasic in the cerebellum. This might be explained by the differences in timing of development of the various neuronal cell types formed in these two brain areas. The 6-kb transcript was detected only at early developmental stages in the two brain areas. Correlating the temporal expression of the 9-kb mRNA to that of high-molecular-weight MAP2 indicates that the accumulation of this protein is in part regulated at a cytoplasmic level.
Insights
Microtubule-associated protein 2 (MAP2) mRNA expression differs between neurons and astrocytes. High-molecular-weight MAP2 mRNA is present in both, while low-molecular-weight MAP2c mRNA is predominant in astrocytes and decreases with cell culture time.
Area of Science:
- Neuroscience
- Molecular Biology
- Cell Biology
Background:
- Microtubule-associated protein 2 (MAP2) is crucial for neuronal development and function.
- MAP2 exists in high- and low-molecular-weight variants, encoded by different mRNA transcripts.
- Understanding the differential expression of MAP2 variants is key to comprehending neuronal and glial development.
Purpose of the Study:
- To investigate the expression patterns of high- and low-molecular-weight MAP2 mRNAs and proteins.
- To analyze the temporal and quantitative differences in MAP2 transcript expression in developing brain regions and cultured cells.
- To elucidate the regulatory mechanisms of MAP2 protein accumulation.
Main Methods:
- Utilized a cDNA probe specific to MAP2 for studying mRNA expression.
- Analyzed MAP2 mRNA and protein expression in cultured neurons and astrocytes.
- Examined MAP2 transcript expression in developing mouse cerebral hemispheres and cerebellum across different developmental stages.
Main Results:
- A 9-kb mRNA encoding high-molecular-weight MAP2 was found in both cultured astrocytes and neurons, with lower levels in astrocytes.
- A 6-kb transcript encoding MAP2c was expressed in neurons and was the predominant MAP2 transcript in astrocytes.
- Both 9-kb and 6-kb transcripts showed decreased levels in late-stage cell cultures. The 9-kb mRNA was present throughout development, exhibiting biphasic expression in the cerebellum, while the 6-kb transcript was detected only at early developmental stages.
Conclusions:
- MAP2 mRNA expression is cell-type specific, with distinct patterns in neurons and astrocytes.
- Developmental expression of MAP2 transcripts varies between brain regions and cell types.
- Protein accumulation of high-molecular-weight MAP2 is, in part, regulated at the cytoplasmic level, suggesting post-transcriptional control mechanisms.