Microbiota-dependent formylated peptide receptor (Fpr1/2) signaling regulates enteric nervous system development and gastrointestinal motility in mice

Formylated peptide receptors 1 and 2 (Fpr1/2 or FPRs) are G-protein-coupled pattern recognition receptors that bind bacterial formylated peptides. The role of FPRs in enteric nervous system (ENS) development and gastrointestinal (GI) motility is unknown. We generated mice with germline, epithelial-, and neural crest-specific deletion of the Fpr1/2 locus and assessed ENS structure and GI motility. We also employed a gestational microbiota suppression model using antibiotic-treated wild-type dams, alongside a transient gestational colonization model in pregnant germ-free mice using auxotrophic Escherichia coli, to determine whether temporary restoration of maternal microbiota-Fpr1/2 signaling can regulate embryonic ENS development. Enteric neuronal density at embryonic day 18.5, postnatal day 2 (P2), and in adult mice was assessed by CLARITY immunostaining and confocal imaging of pan neuronal markers (Tuj1, HuD and Peripherin). Fecal formylated peptide (fMLF) content was measured by mass spectrometry. Gastrointestinal (GI) motility was assessed by stool frequency, total GI transit time, and FITC-Dextran intestinal transit assay. Germline, epithelial and neural crest-specific Fpr1/2 deletion resulted in reduced fetal, postnatal and post weaning ENS density and epithelial innervation with reduced GI motility in post weaned mice. The 3-week-old- pups derived from antibiotic-treated pregnant wildtype dams showed significantly reduced ENS density and GI motility, with reduced fecal fMLF. Critically, transient gestational colonization of pregnant germ-free mice with auxotrophic E. coli significantly improved enteric neuronal density and GI motility in 6-week-old offspring. Collectively our data show that microbiota-Fpr1/2 signaling in the murine gut is critical for normal ENS development and GI motility and identify Fpr1/2 as a potential therapeutic target to correct GI hypomotility. Our data also suggests a cautious approach to antibiotic usage during pregnancy.