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Myelin/oligodendrocyte glycoprotein is alternatively spliced in humans but not mice
P A Ballenthin1, M V Gardinier
1Department of Pathology, Northwestern University Medical School, Chicago, Illinois, USA.
Abstract:
Myelin/oligodendrocyte glycoprotein (MOG) is an integral membrane protein expressed on the oligodendrocyte cell surface and the outermost surface of myelin sheaths. Due to this localization, MOG is a primary target antigen involved in immune-mediated demyelination. We previously reported that MOG is a unique member of the immunoglobulin (Ig) superfamily in that it possesses two large hydrophobic domains. MOG is highly conserved between deduced peptide sequences of rodent and human MOG (approximately 89% identity). We have completed an investigation of alternative splicing within the human and mouse MOG genes. Reverse transcriptase-polymerase chain reaction (RT-PCR) analysis of total cellular RNA isolated from both fetal and adult human central nervous system (CNS) tissues reveals a complex array of alternatively spliced MOG-specific variants and the presence of two novel exons. Exon 3 encodes a short hydrophilic domain containing multiple in-frame termination codons that would result in truncation of MOG prior to translation of its transmembrane domain. Exon 7 encodes an additional hydrophilic domain that replaces MOG's second hydrophobic domain in one splice variant. We also observed that five of our eight MOG variants exhibited an alternative internal 3' splice acceptor within MOG's terminal exon. Surprisingly, no splicing was observed in a developmental study using mouse brainstem RNA.
Insights
Alternative splicing of the myelin/oligodendrocyte glycoprotein (MOG) gene generates unique variants in the human central nervous system. These MOG variants may play a role in immune-mediated demyelination.
Area of Science:
- Neuroscience
- Molecular Biology
- Immunology
Background:
- Myelin/oligodendrocyte glycoprotein (MOG) is crucial for myelin sheath integrity and a key target in demyelinating diseases.
- MOG is an immunoglobulin superfamily member with unique hydrophobic domains, highly conserved across species.
- Understanding MOG's structure and function is vital for addressing immune-mediated neurological disorders.
Purpose of the Study:
- To investigate alternative splicing patterns of the MOG gene in human and mouse central nervous system (CNS) tissues.
- To identify novel exons and splice variants of MOG.
- To analyze the functional implications of MOG alternative splicing.
Main Methods:
- Reverse transcriptase-polymerase chain reaction (RT-PCR) was employed to analyze MOG gene expression.
- Total cellular RNA was isolated from fetal and adult human CNS tissues and mouse brainstem.
- Sequence analysis was performed to identify alternatively spliced MOG variants and novel exons.
Main Results:
- Complex alternative splicing of the MOG gene was observed in human CNS tissues, yielding multiple variants.
- Two novel exons, Exon 3 and Exon 7, were identified, contributing to MOG structural diversity.
- Exon 3 introduces premature termination codons, while Exon 7 alters hydrophobic domains in MOG variants.
- Five of eight human MOG variants showed alternative 3' splice acceptor usage.
- No MOG splicing variations were detected in developmental mouse brainstem RNA.
Conclusions:
- Alternative splicing significantly diversifies MOG protein structure in the human CNS.
- These MOG splice variants, particularly those involving novel exons, may have distinct functional roles.
- Further research is needed to elucidate the precise roles of MOG variants in CNS function and disease.