Tissue-specific isoforms of chicken myomesin are generated by alternative splicing

Area of Science:

• Biochemistry
• Molecular Biology
• Muscle Physiology

Background:

• Myomesin is a high molecular weight protein found in the M-band of striated skeletal and cardiac muscle.
• The M-band plays a crucial role in muscle structure and function.

Purpose of the Study:

• To isolate and characterize tissue-specific isoforms of chicken myomesin.
• To investigate the structural and evolutionary relationships of myomesin with other M-band proteins.

Main Methods:

• Isolation of complementary DNAs (cDNAs) encoding chicken myomesin isoforms.
• Analysis of cDNA sequences to determine protein structure and identify distinct domains.
• Partial analysis of gene structure to understand isoform generation.
• Comparison of amino acid sequences with related muscle proteins.

Main Results:

• Two tissue-specific myomesin isoforms were isolated from chicken skeletal muscle (174 kDa) and heart (182 kDa).
• Distinct C-terminal domains in the isoforms result from alternative splicing of a composite exon.
• Myomesin's core structure comprises five fibronectin type III and seven immunoglobulin-like domains.
• Identical or comparable domain structures were observed in M-protein and skelemin.

Conclusions:

• Chicken myomesin exists as at least two tissue-specific isoforms generated by alternative splicing.
• Myomesin shares structural homology with M-protein and skelemin, suggesting they belong to the same protein subfamily.
• These high molecular weight M-band proteins likely evolved from a common ancestor and play related roles in muscle structure.