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Identification of a new exon of the brain microtubule-associated protein 2
J Guilleminot1, A Langkopf, J Nunez
1INSERM U. 282, CNRS, hormones et différenciation cellulaire, hôpital Henri-Mondor, Créteil, France.
Abstract:
The 5'-region of the transcripts encoding the HMW-(MAP2b) and LMW-(MAP2c) microtubule associated proteins in the brain was amplified by RT-PCR. The sequencing of cloned PCR fragments allowed to identify a new variant of brain HMW-MAP2 which contained, compared to MAP2b, an insertion of 246 bp located downstream the 5'-junction between MAP2b and MAP2c and that does not alter the open reading frame of MAP2b. The number of amino acid residues encoded by this insertion increases the molecular weight by 8.5 kDa i.e. corresponds to the difference in apparent size between MAP2a and MAP2b. A LMW-MAP2 PCR amplification product containing this insertion has been also identified. Genomic Southern blot analysis confirmed that this region belongs to the MAP2 gene and is located on a single exon.
Insights
Researchers discovered a new variant of brain High Molecular Weight Microtubule Associated Protein 2 (HMW-MAP2) with a novel insertion. This finding explains the molecular weight difference between MAP2a and MAP2b isoforms.
Area of Science:
- Neuroscience
- Molecular Biology
- Genetics
Background:
- Microtubule-associated proteins (MAPs) are crucial for microtubule stability and neuronal development.
- The MAP2 gene encodes several protein isoforms, including HMW-(MAP2b) and LMW-(MAP2c).
- Understanding MAP2 variants is essential for comprehending neuronal structure and function.
Purpose of the Study:
- To investigate the 5'-region of transcripts encoding HMW-(MAP2b) and LMW-(MAP2c) microtubule-associated proteins.
- To identify novel variants of brain MAP2 and characterize their genetic basis.
Main Methods:
- Reverse transcription polymerase chain reaction (RT-PCR) amplification of the 5'-region of HMW-(MAP2b) and LMW-(MAP2c) transcripts.
- DNA sequencing of cloned PCR fragments.
- Genomic Southern blot analysis.
Main Results:
- Identification of a new brain HMW-MAP2 variant with a 246 bp insertion downstream the MAP2b/MAP2c junction.
- The insertion does not alter the open reading frame of MAP2b and adds 8.5 kDa to the molecular weight.
- A LMW-MAP2 variant containing this insertion was also identified.
- Genomic Southern blot confirmed the region belongs to the MAP2 gene and is located on a single exon.
Conclusions:
- A novel MAP2 variant, potentially explaining the size difference between MAP2a and MAP2b, has been identified in the brain.
- This variant arises from a 246 bp insertion within a single exon of the MAP2 gene.
- Further research is needed to elucidate the functional implications of this newly identified MAP2 variant.