An interesting study has arisen that has left researchers asking, can genes come back to life? Recently it was discovered that a gene, which was believed to have been non-existent for a long period of time, appeared to have been restored to life during the course of human evolution. This is the first evidence of an infection fighting human IRGM gene which is a member of the Immunity-related GTPases (IRG) found in humans. This gene family plays an important role in the defence against intracellular pathogens. This gene has had a great deal of medical attention recently when mutations of IRGM were associated with the risk of Crohn’s disease. This study was undertaken and led by Evan Eichler’s genome science laboratory at the University of Washington and the Howard Hughes Medical Institute.
According to the researchers in this study, this gene was believed to have been non-existent for at least 25 million years of human primate evolution. The open reading frame (ORF) was restored in all human and great ape lineages. It was found that majority of this gene cluster was eradicated in early primate evolution when it went from multiple copies to a single copy. Scientists have compared Old World and New World monkey species and have proposed that the remaining copy of this gene died in their common ancestor. It is thought that remaining parts of the gene were continually inherited through millions of years of evolution and extraordinarily in the common ancestor of humans and great apes; it could finally be read to produce proteins. Evidence from research suggests that this change was brought about by the insertion of a retrovirus in the ancestral genome.
The truncated IRGM gene is one of only two of its types which can be found in humans. Most mammals besides humans have several types of this gene which help them to fight off germs like tuberculosis and salmonella which invade cells. Structural analysis of this gene also gives insight into a significant functional plasticity in genes which have experienced numerous varieties of pressures from evolution. It was also found that this gene possesses malleability which may be very helpful for genes that fight against new or newly resistant infections.
Scientists involved with this study have now posed a question of whether this gene is functional in humans, or that their recent report represents one of the first documented examples of death and rebirth in genes.
References
Bekpen C, Marques-Bonet T, Alkan C, Antonacci F, Leogrande MB, et al. (2009) Death and Resurrection of the Human IRGM Gene. PLoS Genet 5(3): e1000403. doi:10.1371/journal.pgen.1000403
ScienceDaily. http://www.sciencedaily.com /releases/2009/03/090305204321.htm Accessed 23 March 2009.
