HOX gene complement and expression in the planarian Schmidtea mediterranea

Area of Science:

• Developmental Biology
• Genomics
• Planarian Biology

Background:

• Freshwater planarians exhibit remarkable regenerative capabilities.
• Understanding spatial patterning and tissue re-patterning in adult planarians remains a challenge.
• HOX genes are implicated in spatial patterning, but their full complement and organization in planarians are largely unknown.

Purpose of the Study:

• To investigate the complete set of HOX genes in the freshwater planarian Schmidtea mediterranea.
• To determine the genomic organization and expression patterns of planarian HOX genes.
• To provide a dataset for future research on axial patterning in planarians.

Main Methods:

• Utilized a highly sensitive whole-mount in situ hybridization method to detect HOX genes.
• Performed RNA deep-sequencing across six anterior-posterior zones of the planarian.
• Analyzed genomic data to assess HOX gene clustering.

Main Results:

• Identified 13 HOX genes in Schmidtea mediterranea, representing all major axial categories.
• Demonstrated that planarian HOX genes do not cluster in the genome.
• Observed retained aspects of axially restricted expression in 5 out of 13 HOX genes.

Conclusions:

• Freshwater planarians possess a complex and unappreciated HOX gene repertoire.
• Planarians exhibit a derived body plan with potentially altered HOX gene expression compared to other bilaterians.
• The developed methods and data facilitate further research into planarian anterior-posterior axis patterning.