Graph Based Analysis for Gene Segment Organization In a Scrambled Genome
This work addresses the challenge of understanding complex DNA rearrangement processes in scrambled genomes, specifically for researchers in genomics and bioinformatics, though it is incremental as it applies existing graph and topological methods to a new biological dataset.
The authors tackled the problem of analyzing gene segment organization in scrambled genomes by representing segment relationships as directed graphs and applying topological data analysis to identify patterns. Their analysis of the ciliate Oxytricha trifallax revealed star-like structures where segments of a single gene can interleave with up to fifteen other genes, and up to six genes can have mutually interleaving or overlapping segments.
DNA rearrangement processes recombine gene segments that are organized on the chromosome in a variety of ways. The segments can overlap, interleave or one may be a subsegment of another. We use directed graphs to represent segment organizations on a given locus where contigs containing rearranged segments represent vertices and the edges correspond to the segment relationships. Using graph properties we associate a point in a higher dimensional Euclidean space to each graph such that cluster formations and analysis can be performed with methods from topological data analysis. The method is applied to a recently sequenced model organism \textit{Oxytricha trifallax}, a species of ciliate with highly scrambled genome that undergoes massive rearrangement process after conjugation. The analysis shows some emerging star-like graph structures indicating that segments of a single gene can interleave, or even contain all of the segments from fifteen or more other genes in between its segments. We also observe that as many as six genes can have their segments mutually interleaving or overlapping.