Separate pathways for synapse-specific and electrical activity-dependent gene expression in skeletal muscle

Area of Science:

• Neuroscience
• Molecular Biology
• Genetics

Background:

• Nerve and muscle signaling involves transcriptional regulation of acetylcholine receptor (AChR) genes.
• Innervation influences AChR gene expression through synapse-specific activation and electrical activity-dependent inactivation.
• A 1.8 kb region of the AChR delta subunit gene's 5' flanking DNA mediates these opposing effects.

Purpose of the Study:

• To investigate the DNA sequences responsible for synapse-specific and electrical activity-dependent regulation of AChR gene expression.
• To determine if the same DNA elements and proteins mediate both activation and repression of AChR gene expression.
• To elucidate the role of E-box binding proteins in mediating electrical activity-dependent gene regulation.

Main Methods:

• Generation of transgenic mice carrying acetylcholine receptor (AChR) delta subunit-human growth hormone (hGH) gene fusions.
• Analysis of gene expression patterns in response to varying electrical activity and synaptic signaling.
• Site-directed mutagenesis to identify critical DNA binding sites, specifically the E-box.

Main Results:

• A specific E-box binding site is crucial for electrical activity-dependent regulation but not for synapse-specific regulation of the AChR delta subunit gene.
• These findings indicate that different DNA sequences mediate synapse-specific and electrical activity-dependent gene expression.
• The cis-acting elements for both innervation-dependent regulatory aspects are localized within 181 bp of the AChR delta subunit gene's 5' flanking DNA.

Conclusions:

• Electrical activity-dependent regulation of AChR gene expression involves changes in the expression or activity of E-box binding proteins.
• Synapse-specific and electrical activity-dependent gene expression are controlled by distinct DNA sequences.
• A compact 181 bp region of the AChR delta subunit 5' flanking DNA contains the regulatory elements for both innervation-dependent processes.