Sometimes I am asked whether a pseudogene can regain function. The answer, according to a paper by Bekpen et al. (2009), is yes. And the mechanism is cool — an Alu insertion knocked it out and an ERV insertion restored its function.
The IRG gene family plays an important role in defense against intracellular bacteria, and genome-wide association studies have implicated structural variants of the single-copy human IRGM locus as a risk factor for Crohn’s disease. We reconstruct the evolutionary history of this region among primates and show that the ancestral tandem gene family contracted to a single pseudogene within the ancestral lineage of apes and monkeys. Phylogenetic analyses support a model where the gene has been “dead” for at least 25 million years of human primate evolution but whose ORF became restored in all human and great ape lineages. We suggest that the rebirth or restoration of the gene coincided with the insertion of an endogenous retrovirus, which now serves as the functional promoter driving human gene expression. We suggest that either the gene is not functional in humans or this represents one of the first documented examples of gene death and rebirth.
This story has already been reported by others, so I will just post links:
The death and resurrection of IRGM – the “Jesus gene” (Not Exactly Rocket Science)
First ‘resurrected’ gene found in humans (New Scientist)
The resurrection of a disease-linked gene (Nature News)
A Curious Case of Genetic Resurrection (ScienceNOW)
(Please don’t get into the whole “aha — scientists shoulnd’t have dismissed Alu and ERVs as junk” trap — see the quotes of interest series).