m6A modifications regulate intestinal immunity and rotavirus infection.

Area of Science:

• Epigenetics and RNA modifications
• Virology and host-pathogen interactions
• Immunology and innate immunity

Background:

• N6-methyladenosine (m6A) is a prevalent mRNA modification influencing biological processes.
• The role of m6A in intestinal antiviral immunity, particularly during rotavirus (RV) infection, remains largely unexplored.
• Understanding m6A regulation and function is critical for developing host-directed antiviral strategies.

Purpose of the Study:

• To investigate the role of m6A modification in intestinal epithelial cells (IECs) during rotavirus infection.
• To identify key m6A targets and elucidate the underlying antiviral signaling mechanisms.
• To explore the age-dependent changes in m6A modification and their implications for neonatal immunity.

Main Methods:

• Utilized genetically modified mice lacking the m6A writer enzyme METTL3 in IECs (Mettl3ΔIEC).
• Employed RNA-sequencing and m6A RNA immunoprecipitation (RIP)-sequencing to identify m6A targets.
• Assessed viral load, interferon (IFN) and IFN-stimulated gene (ISG) expression, and mRNA stability.

Main Results:

• Rotavirus infection down-regulated the m6A eraser ALKBH5, increasing global m6A levels.
• Mettl3ΔIEC mice exhibited resistance to RV infection, characterized by elevated IFN and ISG expression.
• IRF7 was identified as a key m6A target; its mRNA stability and subsequent IFN responses were enhanced in Mettl3-deficient IECs.
• IRF7 deficiency in Mettl3ΔIEC mice restored RV susceptibility and attenuated IFN/ISG responses.
• Global m6A modification significantly decreased with age in mice, particularly between 2 and 3 weeks post-birth.

Conclusions:

• A novel host antiviral signaling cascade involving m6A modification, IRF7, and IFN production restricts rotavirus infection in vivo.
• METTL3-mediated m6A modification of IRF7 is essential for robust intestinal antiviral immunity.
• Age-related decline in m6A modification may impact the developing intestinal immune system's ability to combat enteric viral infections.