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A novel transcript overlapping the myelin basic protein gene
B Grima1, D Zelenika, B Pessac
1Centre de Biologie Cellulaire du CNRS, ERS 28, Ivry/Seine, France.
Abstract:
Myelin basic protein (MBP) is a major constituent of myelin synthesized by oligodendrocytes and Schwann cells. We have investigated the expression of mouse MBP RNAs outside the nervous system. Nuclease protection experiments indicate that RNAs containing exon 1 and not the six downstream exons of the MBP gene are transcribed in various hemopoietic tissues. We have isolated a hemopoietic MBP-related (HMBPR) cDNA clone from a mouse bone marrow cDNA library screened with an MBP cDNA probe. This clone contains exons 1a and 1b and a part of intron 1 of the MBP gene. An additional 5' region, encoded by at least three unidentified exons, lies upstream of exon 1a. The HMBPR clone corresponds to a 5-kb RNA expressed in bone marrow, spleen, thymus, and macrophagic cells. This transcript is expressed at a similar level in brain, although at a lower level than the classical 2-kb mRNA. These data indicate that a new transcript, overlapping the MBP transcription unit and controlled by a distinct promoter, is expressed in hemopoietic tissues. This RNA might encode a 21-kDa protein sharing a common domain with MBP.
Insights
Researchers discovered a novel RNA transcript in mouse hemopoietic tissues, distinct from classical myelin basic protein (MBP) mRNA. This new transcript, potentially encoding a 21-kDa protein, originates from a separate promoter within the MBP gene locus.
Area of Science:
- Neuroscience
- Molecular Biology
- Immunology
Background:
- Myelin basic protein (MBP) is a key component of myelin, crucial for nerve insulation.
- MBP is primarily synthesized by oligodendrocytes and Schwann cells in the nervous system.
Purpose of the Study:
- To investigate the expression of mouse MBP RNAs outside the central nervous system.
- To identify and characterize novel MBP-related transcripts in hemopoietic tissues.
Main Methods:
- Nuclease protection experiments to analyze RNA transcripts.
- Screening of a mouse bone marrow cDNA library using an MBP cDNA probe.
- Isolation and characterization of a hemopoietic MBP-related (HMBPR) cDNA clone.
Main Results:
- RNAs containing only exon 1 of the MBP gene are transcribed in various hemopoietic tissues.
- A novel 5-kb HMBPR transcript was identified in bone marrow, spleen, and thymus.
- This transcript shares sequence homology with MBP and is expressed in macrophagic cells and brain.
Conclusions:
- A new transcript, overlapping the MBP gene, is expressed in hemopoietic tissues.
- This transcript is controlled by a distinct promoter, suggesting alternative gene regulation.
- The HMBPR RNA may encode a 21-kDa protein with a shared domain with MBP, indicating a potential role in hemopoiesis or immune function.