Cloning and characterization of the myelin basic protein gene from mouse: one gene can encode both 14 kd and 18.5 kd MBPs by alternate use of exons
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Abstract:
A mouse cosmid library was screened with a cDNA clone for rat small (M, 14,000) myelin basic protein (MBP). The entire MBP gene was isolated. Five exons were detected with the cDNA clone, which encode the Mr 14,000 MBP. A sixth exon, detected using a synthetic oligonucleotide, encodes the 41 amino acids specific to the Mr 18,500 form of MBP. Splicing together all six exons would give rise to Mr 18,500 MBP, while an mRNA omitting exon V would be translated to produce Mr 14,000 MBP. Further experiments indicate that there is probably a single MBP gene in the mouse genome, and that there is a single major 5' end for mouse MBP transcripts, 47 bp 5' of the initiator methionine codon.
Insights
Researchers identified the complete mouse myelin basic protein (MBP) gene, revealing six exons. Alternative splicing of these exons generates different MBP protein isoforms, crucial for myelin structure and function.
Area of Science:
- Molecular Biology
- Neuroscience
- Genetics
Background:
- Myelin basic protein (MBP) is a major component of the myelin sheath in the central nervous system.
- MBP exists in multiple isoforms, with the 14,000 and 18,500 M r forms being well-characterized.
- Understanding the genetic basis of MBP isoforms is essential for comprehending myelin development and disorders.
Purpose of the Study:
- To isolate and characterize the complete mouse myelin basic protein (MBP) gene.
- To elucidate the genetic mechanisms underlying the generation of different MBP isoforms.
- To identify the transcriptional start site of mouse MBP.
Main Methods:
- Screening of a mouse cosmid library using a rat MBP cDNA clone.
- Exon detection via cDNA hybridization and synthetic oligonucleotide probing.
- Analysis of mRNA splicing patterns and transcriptional start sites.
Main Results:
- The entire mouse MBP gene was isolated, comprising six exons.
- Five exons encode the 14,000 M r MBP, while a sixth exon adds 41 amino acids for the 18,500 M r form.
- A single MBP gene and a major transcription start site were identified in the mouse genome.
Conclusions:
- The mouse MBP gene structure supports the generation of distinct MBP isoforms through alternative splicing.
- Alternative splicing of exon V is responsible for producing the 14,000 M r MBP.
- The identified transcriptional start site provides insights into MBP gene regulation.