Regeneration: Why junk DNA might matter

The ability of certain natural species to restore or regenerate missing structures has been a recurrent source of inspiration to forge our collective knowledge, from being used to adorn mythological figures with superhuman powers to permitting controlled reproducible observations that help setting the bases of entire research fields such as experimental biology and regenerative medicine. In spite of being one of the oldest natural phenomena under study, what makes certain species able or unable to regenerate missing parts is still largely a mystery. Recent advancements towards the highly detailed characterization of the sequence, the spatial organization, and the expression of genomes is offering a new standpoint to address the study of the natural variation in regenerative responses. An intriguing observation that has not yet conveniently pursued is that species with remarkable regenerative abilities tend to have genomes loaded with junk DNA (jDNA), i.e., genetic elements presumed to be useless for the benefit of the individual, whereas species for taxa with limited regenerative abilities tend to have jDNA-poor genomes. Here, I use existing knowledge on the role of jDNA as genome evolution facilitator and its non-random chromosome and nuclear distributions to speculate about two non-excluding ways through which the variation in jDNA genomic content might end up enhancing or limiting regenerative responses. The present piece aims to go beyond the confines of correlational studies between biological variables and to lay sensible conceptual grounds for future hypothesis-driven attempts to substantiate the genomic determinants of the natural variation of regenerative responses.