Gcm: a novel anti-inflammatory transcriptional cascade conserved from flies to humans

Innate immunity is an ancestral process that can induce pro- and anti-inflammatory states. A major challenge is to characterise the transcriptional cascades that modulate the response to chronic and acute inflammatory challenges. The Drosophila melanogaster Gcm transcription factor represents an interesting candidate for its potential anti-inflammatory role. Here we explore its evolutionary conservation and its mode of action. We found that the murine ortholog Gcm2 (mGcm2) is expressed upon aging, which is considered as a state of chronic inflammation. mGcm2 is found in a subpopulation of microglia, the innate immune cells of the central nervous system (CNS). Its expression is also induced by a lyso-phosphatidylcholine (LPC)-induced CNS demyelination (acute inflammation) and mGcm2 conditional knock out mice show an increased inflammatory phenotype upon aging or LPC injection. In agreement with the role of this transcriptional cascade in inflammation, the human ortholog hGCM2 is expressed in active demyelinating lesions of Multiple Sclerosis (MS) patients. Finally, Drosophila gcm expression is induced upon aging as well as during an acute inflammatory response and its overexpression decreases the inflammatory phenotype. Altogether, our data show that the inducible Gcm pathway is highly conserved from flies up to humans and represents a potential therapeutic anti-inflammatory target in the control of the inflammatory response.