Identification of three forms of human myelin basic protein by cDNA cloning

Area of Science:

• Neuroscience
• Molecular Biology
• Genetics

Background:

• Myelin basic protein (MBP) is a key component of the myelin sheath.
• Alternative splicing of mRNA is a common mechanism for generating protein diversity.

Purpose of the Study:

• To isolate and characterize cDNA clones for human myelin basic protein (MBP).
• To investigate the molecular basis for different human MBP isoforms.
• To compare the human MBP gene structure with that of the mouse.

Main Methods:

• cDNA cloning and nucleotide sequencing of human MBP forms.
• Immunoblot analysis using specific antisera.
• Southern blotting of human genomic DNA.

Main Results:

• Three distinct human MBP forms (21.5, 18.5, and 17.2 kDa) were isolated and sequenced.
• Human MBP isoforms differ by the inclusion/exclusion of specific amino acid sequences, corresponding to mouse MBP exons 2 and 5.
• Evidence suggests a single human MBP gene undergoes alternative splicing to produce these variants.
• The 21.5-kDa human MBP was identified using antibodies against a mouse exon 2 peptide.

Conclusions:

• The three human MBP mRNAs result from alternative splicing of a primary transcript.
• The human and mouse MBP genes share a similar exon structure.
• The conserved 26-amino acid sequence (mouse exon 2) in human MBP likely plays a crucial role in myelination.