Phd in CELL AND DEVELOPMENTAL BIOLOGY

Thesis title: Cross-talk between gut microbiota and brain: effects of probiotics on the endophenotype of R451C Neuroligin3 monogenic mouse model of autism

The focus of my doctoral thesis was to investigate the connection between the central nervous system and the gut, mediated by the “gut-brain axis,” in the monogenic mouse model of autism expressing the human mutation Neuroligin3 R451C. The effects of five probiotic and potential probiotic strains belonging to the family Lactobacilli have been tested on reverting the impaired social behavior and biochemical pathways in the R451C Neuroligin3 knock-in mice. Across all experiments, a consistent finding was the rescue of the compromised social phenotype after the treatment with each of the five bacterial strains. This result not only supports the growing evidence that probiotics promote the restoration of a balanced gut microbiota, thereby exerting beneficial effects on the brain via circulating molecules and vagal signaling, but also highlights the previously unrecognized probiotic potential of four strains (A mix of Lactiplantibacillus plantarum C9O4 and LT52, Periweissella beninensis LMG 25373T, and Lactiplantibacillus plantarum H64) while confirming the established activity of Lactobacillus reuteri АТСС РТА 6475, already used in humans. Building on the behavioral improvements observed in one of the core symptoms of autism, namely altered social interaction, I performed comprehensive biochemical analyses in the absence and after the treatment with each of the different strains. I examined excitatory and inhibitory synaptic proteins levels known to be altered in the central nervous system of R451C Neuroligin3 mice, as well as amino acids and neurotransmitter levels, components of the endocannabinoid system (receptors and circulating molecules levels), and the unfolded protein response, known to be activated in the cerebellum of our animal model. Moreover, we have analyzed potential changes in gut microbiota composition, intestinal permeability, and peripherical immune activation. Taken together, the results indicate that although all strains rescue the social deficits, they act through distinct mechanisms to ameliorate the altered biochemical phenotypes of the R451C Neuroligin3 mouse model. By shaping the gut microbiota and favoring “gut-supporter taxa,” these strains differentially engage gut-brain communication pathways, ultimately restoring behavioral and molecular homeostasis.