Spatial transcriptomics reveals a cnidarian segment polarity program in Nematostella vectensis

Area of Science:

• Developmental Biology
• Evolutionary Biology
• Genetics

Background:

• Axially polarized segments were fundamental to the evolution of complex bilaterian body plans.
• The precise origin and molecular mechanisms of segment polarity pathways remain largely unknown.

Purpose of the Study:

• To elucidate the molecular basis of segment polarization in the early evolution of animal body plans.
• To investigate the roles of conserved genes in establishing segment polarity in the sea anemone Nematostella vectensis.

Main Methods:

• Spatial transcriptomics to create a 3D gene expression atlas of developing larval segments.
• In silico predictions to identify key regulatory genes.
• Functional analysis using Lbx mutagenesis to assess the impact on segment polarity.

Main Results:

• Identified Lbx and Uncx homeodomain genes in opposing subsegmental domains, regulated by BMP signaling and the Hox-Gbx cascade.
• Lbx gene mutation abolished molecular evidence of segment polarization in larvae.
• Lbx mutagenesis resulted in abnormal mirror-symmetric retractor muscles in primary polyps.

Conclusions:

• Demonstrated the molecular basis for segment polarity in a non-bilaterian (Nematostella vectensis).
• Suggests that polarized metameric structures were present in the Cnidaria-Bilateria common ancestor over 600 million years ago.
• Provides insights into the early evolution of animal segmentation and body plan development.