As a human, if you lose a limb, you’re unable to grow a new one. However, a number of species including amphibians and fish have the remarkable ability to regenerate fully functional appendages after loss, forming new tissue including bone, muscle, nerves, and blood vessels. Scientists studying regeneration have noted that a key stage in the process is the formation of an unspecialized tissue known as “blastema,” but little was previously known about the genetic regulation of blastema formation.
Benjamin King and Viravuth Yin from Mount Desert Island Biological Laboratory and the University of Maine set out to investigate the regulatory circuits acting in blastema formation. They studied three evolutionarily distant species, one salamander and two ray-finned fish, to discover if the genes involved in this process were conserved or if they differed between species.
King and Yin analysed tissue samples from these species, taken from regenerating limbs at various times following amputation, and conducted RNA sequencing to identify microRNAs regulating blastema formation in each species.
They found that a core group of microRNAs likely involved in regulation of blastema formation were conserved across all three species, despite these species being evolutionarily distant. The authors also worked to identify putative gene targets of these microRNAs, which included a number not previously known to act in regeneration. The authors suggest that limb regeneration across species may involve a common regulatory genetic pathway, even across evolutionarily distant organisms that diverged ~420 million years ago.
Studying regeneration in other species could inform clinical work on inducing new tissue formation in humans. Understanding the genetic regulation of blastema formation during limb regeneration may therefore eventually help to develop human tissue therapies.
Research Article: King BL, Yin VP (2016) A Conserved MicroRNA Regulatory Circuit Is Differentially Controlled during Limb/Appendage Regeneration. PLoS ONE 11(6): e0157106. doi:10.1371/journal.pone.0157106