The evolution of tenascins

Area of Science:

• Evolutionary biology
• Molecular evolution
• Genomics

Background:

• Extracellular matrix evolution is linked to organogenesis in metazoans.
• Tenascins are chordate extracellular matrix glycoproteins involved in cell signaling and morphogenesis.
• The evolutionary history of the tenascin gene family, with its multiple vertebrate paralogs, remains unclear.

Purpose of the Study:

• To investigate the evolutionary origins and diversification of tenascin proteins across chordate lineages.
• To construct an evolutionary model for the tenascin gene family.

Main Methods:

• Genomic analysis of hemichordates, cephalochordates, tunicates, agnathans, cartilaginous fishes, lobe-finned fishes, ray-finned fishes, and tetrapods.
• Identification of predicted tenascin proteins.
• Assessment of evolutionary relationships using sequence conservation, molecular phylogeny, and gene synteny conservation.

Main Results:

• A new evolutionary model for tenascin origin in ancestral chordates is proposed.
• Tenascin-C-like and tenascin-R-like paralogs emerged after a vertebrate whole genome duplication.
• Tenascin-X arose from a second gnathostome whole genome duplication, and tenascin-W from a local duplication of tenascin-R.

Conclusions:

• Tenascin paralog diversity in vertebrates resulted from selective gene retention after whole genome and local duplications.
• The emergence of specific tenascin paralogs correlates with the development of vertebrate-specific tissues.
• Examples include tenascin-C in the craniofacial skeleton, tenascin-R in the central nervous system, and tenascin-W in bone.