Human nicotinic acetylcholine receptor alpha-subunit isoforms: origins and expression

Area of Science:

• Immunology
• Molecular Biology
• Neuroscience

Background:

• Myasthenia gravis (MG) involves autoantibodies targeting the nicotinic acetylcholine receptor (AChR) alpha-subunit.
• Human AChR alpha-subunit exhibits two isoforms due to alternative splicing of the P3A exon, potentially impacting MG pathogenesis.

Purpose of the Study:

• To investigate the presence and expression of the P3A exon in the AChR alpha-subunit across species.
• To determine if P3A exon expression is altered in human tissues or during MG development.

Main Methods:

• Genomic sequencing of AChR alpha-subunit exons P3-P4 in rhesus monkey, dog, and cat.
• RT-PCR analysis to detect P3A exon expression in various species and human tissues.
• Analysis of P3A isoform expression during fetal muscle development and in MG patient muscle.

Main Results:

• Homologous regions to the P3A exon were found in non-human primates and susceptible mammals, but were not expressed.
• Constitutive expression of the P3A+ alpha-subunit mRNA was not detected in human heart, kidney, liver, lung, or brain.
• No differential expression of the two alpha-subunit isoforms was observed during fetal muscle development or in muscle from MG patients.

Conclusions:

• The P3A exon, responsible for a human AChR alpha-subunit isoform, is not expressed in tested non-human mammals.
• P3A exon expression in humans is not restricted to specific tissues and is not altered in myasthenia gravis.
• The two human AChR alpha-subunit isoforms are expressed at a roughly 1:1 ratio when detected.