Aicardi-Goutières syndrome-like encephalitis in mutant mice with constitutively active MDA5

Area of Science:

• Immunology
• Neuroscience
• Genetics

Background:

• MDA5 (Melanoma Differentiation-Associated gene 5) is a cytoplasmic RNA sensor crucial for type I interferon (IFN-I) production.
• Constitutively active MDA5 is implicated in autoimmune disorders like Aicardi-Goutières syndrome (AGS), a severe inflammatory encephalopathy.
• Research into AGS is hindered by the scarcity of suitable animal models.

Purpose of the Study:

• To investigate the role of constitutively active MDA5 in early-onset neurological disease.
• To establish and characterize a novel mouse model for Aicardi-Goutières syndrome (AGS).
• To explore the involvement of microglia and IFN-I signaling in the pathogenesis of AGS.

Main Methods:

• Generation and analysis of Ifih1G821S/+ mice with constitutively active MDA5.
• Assessment of survival rates, neurological symptoms, and IFN-I production in postnatal mice.
• Histopathological examination of brain tissue, including microglial analysis and immune cell infiltration.
• Analysis of auto-antibodies in serum and comparison with AGS patient data.

Main Results:

• Ifih1G821S/+ mice exhibit high postnatal lethality and spontaneous encephalitis.
• Encephalitis is characterized by elevated IFN-I production and increased, activated microglia with enhanced phagocytic capacity.
• Microglial activation and encephalitis occur independently of auto-antibodies and lymphocytes, mirroring AGS features.
• Ifih1G821S/+Rag2-/- mice confirm IFN-I driven pathology without lymphocytic infiltration.

Conclusions:

• The Ifih1G821S/+ mouse model recapitulates key features of Aicardi-Goutières syndrome (AGS).
• IFN-I signaling and microglial activation are central to the pathogenesis of MDA5-associated encephalopathy.
• Targeting microglia represents a promising therapeutic strategy for AGS.