Bacterial Peptidoglycans from Microbiota in Neurodevelopment and Behavior.

It is increasingly recognized that the gut microbiota profoundly influences many aspects of host development and physiology, including the modulation of brain development and behavior. However, the precise molecular mechanisms and signaling pathways involved in communication between the microbiota and the developing brain remain to be fully elucidated. Germline-encoded pattern-recognition receptors (PRRs) that recognize conserved microbial molecular signatures such as bacterial surface molecules (e.g., peptidoglycans, PGNs) have emerged as potential key regulators of gut microbiota-brain interactions. We highlight current evidence supporting multiple and essential roles for PGNs and their sensing molecules beyond innate immunity, extending to neurodevelopment and behavior. In addition, the possible implications of the PGN signaling pathway for the pathogenesis of neurodevelopmental disorders such as autism spectrum disorder (ASD) are considered.