Comparative Cytogenetic Mapping and Telomere Analysis Provide Evolutionary Predictions for Devil Facial Tumour 2.

Area of Science:

• Genetics
• Evolutionary Biology
• Cancer Biology

Background:

• Tasmanian devils face a threat from transmissible cancers.
• Devil facial tumour 2 (DFT2) is a newly emerged transmissible cancer.
• Understanding DFT2 evolution is crucial for conservation.

Purpose of the Study:

• To investigate the evolutionary trajectory of chromosome rearrangements in DFT2.
• To compare DFT2 evolution with DFT1.
• To predict the future genomic stability of DFT2.

Main Methods:

• Cytogenetic mapping
• Telomere length measurements
• Fluorescence in situ hybridization (FISH)
• Long-term cell culture

Main Results:

• Identified two distinct DFT2 lineages.
• Both DFT1 and DFT2 originated from chromosome fusions forming dicentric chromosomes.
• DFT2 stabilized via centromere silencing, resulting in a less rearranged karyotype than DFT1.
• DFT2 maintained telomere length dimorphism, a feature lost in DFT1.

Conclusions:

• DFT2's evolutionary path involved chromosomal stabilization, unlike DFT1's extensive rearrangements.
• DFT2 is predicted to have limited further chromosomal evolution due to stable telomere lengths.
• The study provides insights into the genomic evolution of transmissible cancers.