title: Host microbiota modulates development of social preference in mice.
abstract: BACKGROUND
  Mounting evidence indicates that the indigenous gut microbiota exerts long-lasting programming effects on brain function and behaviour.
  
  
  OBJECTIVE
  In this study, we used the germ-free (GF) mouse model, devoid of any microbiota throughout development, to assess the influence of the indigenous microbiota on social preference and repetitive behaviours (e.g. self-grooming).
  
  
  RESULTS
  Using the three-chambered social approach task, we demonstrate that when adult GF mice were given a choice to spend time with a novel mouse or object, they spent significantly more time sniffing and interacting with the stimulus mouse compared to conventionally raised mice (specific pathogen-free, SPF). Time spent in repetitive self-grooming behaviour, however, did not differ between GF and SPF mice. Real-time PCR-based gene expression analysis of the amygdala, a key region that is part of the social brain network, revealed a significant reduction in the mRNA levels of total brain-derived neurotrophic factor (BDNF), BDNF exon I-, IV-, VI-, IX-containing transcripts, and NGFI-A (a signalling molecule downstream of BDNF) in GF mice compared to SPF mice.
  
  
  CONCLUSIONS
  These results suggest that differential regulation of BDNF exon transcripts in the amygdala by the indigenous microbes may contribute to the altered social development of GF mice.
authors.affiliation: Department of Neuroscience, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Tim
authors.initials: T
authors.lastname: Arentsen
authors.affiliation: Department of Neuroscience, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Henrike
authors.initials: H
authors.lastname: Raith
authors.affiliation: Department of Neuroscience, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Yu
authors.initials: Y
authors.lastname: Qian
authors.affiliation: Department of Women's and Children's Health, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Hans
authors.initials: H
authors.lastname: Forssberg
authors.affiliation: Department of Neuroscience, Karolinska Institutet, Stockholm, Sweden; rochellys.heijtz@ki.se.
authors.forename: Rochellys
authors.initials: R
authors.lastname: Diaz Heijtz
keywords: BDNF; amygdala; brain development; gene expression; germ-free mice; synaptic plasticity genes