Ancient animal ancestry for nuclear myosin

Area of Science:

• Evolutionary biology
• Molecular biology
• Cell biology

Background:

• The discovery of nuclear myosin I (NMI) suggests myosin proteins may have had ancestral functions within the eukaryotic nucleus.
• Understanding the evolutionary history of myosin I is crucial to determining its early roles.

Purpose of the Study:

• To investigate the evolutionary origins and diversification of vertebrate myosin-I proteins.
• To determine if the nuclear localization of myosin I predates the emergence of vertebrates.

Main Methods:

• Phylogenetic analysis of vertebrate myosin-I protein sequences.
• Comparative genomics to trace gene duplication events.
• Examination of myosin-I protein localization in non-vertebrate model organisms (e.g., Ciona intestinalis).

Main Results:

• Myosin I underwent significant gene duplication events in early vertebrate evolution, resulting in nine distinct gene families.
• Phylogenetic analysis indicates that the nuclear function of myosin I predates these vertebrate-specific duplications.
• A myosin-I protein in the tunicate Ciona intestinalis localizes to the nucleus, branching evolutionarily before key vertebrate myosin I lineages.

Conclusions:

• The nuclear localization of myosin I predates the origin of vertebrates, suggesting an ancient functional role.
• Nuclear myosin I was present in the last common ancestor of vertebrates and tunicates, indicating a role early in animal evolution.
• The expansion of myosin-I gene families in vertebrates likely facilitated adaptive radiation of myosin-I functions.