Mouse Paneth cell antimicrobial function is independent of Nod2

Area of Science:

• Microbiology
• Immunology
• Genetics

Background:

• Polymorphisms in the NOD2 gene are linked to ileal Crohn's disease susceptibility.
• Previous studies suggested Nod2 deficiency reduces Paneth cell antimicrobial peptide (AMP) expression, but mouse strain specifics were unclear.
• Mouse strain significantly impacts Paneth cell antimicrobial activity, necessitating background-specific investigation.

Purpose of the Study:

• To investigate the role of NOD2 in regulating Paneth cell (PC) antimicrobial peptide (AMP) expression and function in C57BL/6 (B6) mice.
• To determine if Nod2(-/-) B6 mice exhibit reduced AMP expression and activity.
• To assess the impact of NOD2 deficiency on gut microbial composition in a controlled environment.

Main Methods:

• Quantitative real-time PCR, acid urea polyacrylamide gel electrophoresis, and mass spectrometry were used to assess ileal AMP expression in wild-type (WT) and Nod2(-/-) B6 mice.
• Paneth cells were enumerated via flow cytometry.
• Antimicrobial activity of α-defensins was evaluated using a gel-overlay assay, and fecal microbial composition was analyzed using 16S rRNA gene sequencing in cohoused littermates.

Main Results:

• Wild-type and Nod2(-/-) B6 mice showed comparable Paneth cell AMP expression levels and α-defensin profiles.
• No significant differences in antimicrobial activity against bacterial strains were observed between WT and Nod2(-/-) B6 mice.
• Cohoused WT and Nod2(-/-) littermates exhibited minimal differences in fecal microbial composition.

Conclusions:

• NOD2 does not directly regulate Paneth cell antimicrobial activity in the C57BL/6 mouse model.
• Environmental factors, such as cohousing with wild-type littermates, can mitigate previously observed NOD2-dependent effects on gut microbial composition.