Genome fragmentation in the ageing culture of Paramecium tetraurelia

Although unicellular, the ciliate Paramecium tetraurelia shows ageing phenotype in the course of clonal growth. The highly-polyploid chromosome of the macronucleus (the transcriptionally-active nucleus in the clonal life stage) receive genome fragmentation in the clonal growth, and it is believed to be the cause of the ageing phenotype. To detect and understand the age-induced genome fragmentation, we developed a method to enrich the fragmentation sites which are sealed by de novo telomeres (Subtle-seq; Subtelomere Enrichment-sequencing) by combining Exonuclease III digestion and sequence-specific PCR. The reads containing UMI were sequenced by NovaSeq 6000 SP platform. We identified numerous genome fragmentation sites in the aged Paramecium and the enrichment on specific genome features.