Absence of the functional Myosin heavy chain 2b isoform in equine skeletal muscles.

The research article investigates the absence of the Myosin heavy chain (MyHC) 2b isoform in equine skeletal muscles, implying that the MyHC-2b gene lost its function in horses and some other ungulate species during evolution.

Methodology

The researchers conducted a study on equine skeletal muscles’ nucleotide sequences, determining the full coding regions for three types of myosin heavy chain (MyHC) isoforms. They sought MyHC-2a, -2x, and -slow, specific genes that produce proteins responsible for muscle contraction. The researchers then analyzed the results using PCR amplifications and specific primers to confirm the presence of the MyHC-2b and -2x genes.

• PCR (polymerase chain reaction) is a laboratory method used to make millions of copies of a specific DNA segment in order to analyze it more easily.
• Primers are short pieces of DNA that serve as a starting point for DNA synthesis, crucial to the PCR process.

Findings

The research revealed that there was no amplification of the MyHC-2b isoform from the equine muscle cDNA except for a pseudogene fragment. A pseudogene is a DNA sequence that resembles a gene but has been mutated and, as a result, does not function as regular genes do.

• In this case, the pseudogene had one inserted nucleotide in its coding region, with only a small amount expressing in the skeletal muscle.
• This pseudogene’s sequence was categorized into the MyHC-2b genes on the phylogenetic tree, linking it to evolutionary relationships among species.

The results from the PCR analyses of other ungulates (hoofed mammals) like rhinoceros, sika deer, moose, giraffes, water buffalo, bovine, Japanese serow, and sheep indicated an absence of the MyHC-2b-specific sequence in their genomes.

Conclusion

The findings suggest the absence of the functional MyHC-2b isoform in equine skeletal muscles and in some other ungulate species. This indicates that the MyHC-2b gene may have independently lost its function over evolutionary history. The reason behind this genetic loss and the potential impacts on the species’ muscle function, however, was not explained and might require further investigation.