Nuclear envelope transmembrane proteins (NETs) that are up-regulated during myogenesis

Area of Science:

• Cell Biology
• Molecular Biology
• Biochemistry

Background:

• The nuclear lamina, a protein meshwork at the inner nuclear membrane, is vital for nuclear structure, gene expression, and cytoskeleton interaction.
• Nuclear lamins and associated transmembrane proteins form the lamina; mutations in lamins cause human diseases, particularly affecting skeletal muscle.
• A previous proteomics study identified 67 novel putative nuclear envelope transmembrane proteins (NETs).

Purpose of the Study:

• To investigate the expression of novel NETs during C2C12 myoblast differentiation.
• To identify new nuclear envelope and lamina components coordinated with muscle differentiation.
• To explore potential roles of identified NETs in muscle development and maintenance.

Main Methods:

• Transcriptional microarray analysis to assess NET expression during myoblast differentiation.
• Quantitative RT-PCR to confirm microarray findings.
• Epitope tagging and immunoblotting to determine NET localization and enrichment at the nuclear envelope.

Main Results:

• Six of the 67 identified NETs showed significantly increased expression during myoblast differentiation.
• All six NETs were highly expressed in adult mouse skeletal muscle compared to nine other tissues.
• Five NETs were confirmed to localize to the nuclear envelope in C2C12 cells and were enriched in purified nuclear envelopes.
• Four of the upregulated NETs possess homology regions suggesting potential signaling functions.

Conclusions:

• Six NETs were identified with predicted roles in muscle development and/or maintenance, based on expression patterns.
• Five of the identified NETs are confirmed as authentic nuclear envelope proteins.
• Four NETs may have signaling functions at the nuclear envelope, indicated by sequence homology.