A team of scientists from across the globe have found that gut bacteria may influence mammalian brain development and adult behavior. Dr Martin Hibberd from the Genome Institute of Singapore (GIS), in collaboration with Dr Sven Petterssons and Dr Rochellys Diaz-Heijtz from the Karolinska Institutet (KI), and Dr Hans Forssberg from the Stockholm Brain Institute, compared behavior and gene expression in two groups of mice – those raised with normal microorganisms and those raised in the absence of microorganisms (or germ-free (GF) mice). They observed that adult GF mice displayed different behavior from those raised with normal microorganisms, suggesting that gut bacteria may have a significant effect on the development of the brain in mammals.

The researchers observed that adult GF mice were more active and engaged in more “risky” behavior than mice raised with normal microorganisms. When GF mice were exposed to normal microorganisms very early in life, as adults they developed the behavioral characteristics of those exposed to microorganisms from birth. In contrast, colonizing adult GF mice with bacteria did not influence their behavior.

Subsequent gene profiling in the brain identified genes and signaling pathways involved in learning, memory and motor control that were affected by the absence of gut bacetria, highlighting the profound changes in the mice that developed in the absence of microorganisms. This suggests that, over the course of evolution, colonization of gut by microorganisms in early infancy became integrated into early brain development.

“These studies are the results from a systematic genomic approach to understand host microbe interactions that was initiated several years ago and supported by the GIS and its director, Edison Liu. It is an illustration of how this data-driven approach can generate unexpected results and lead you to new directions, with very novel findings,” said Dr Pettersson, co-ordinator of this international study, and Dr Hibberd.

The data suggests that there is a critical period early in life when gut microorganisms affect the brain and change the behavior in later life”, said Dr Diaz-Heijtz. Added Dr Pettersson, “Not only are signal substances like serotonin and dopamine subject to regulation by bacteria, synapse function also appears to be regulated by colonizing bacteria. Our findings, presented today, are a result of a long-standing and ongoing collaboration between KI and the GIS in Singapore, aimed at exploring host-microbe interactions in a systematic manner.”

Dr Hibberd said, “This work builds upon our understanding of how our genome interacts with the microbial world, leading to a new and exciting understanding of how humans might benefit from our interaction with microbes. We hope to continue our collaboration with KI and the Stockholm Brain Institute to explore this new frontier of scientific knowledge.”

Notes

Research publication:

The research findings described in the press release can be found in the 31 January, 2011 advance online issue of Proc Nat. Acad Sci USA under the title “Normal gut microbiota modulates brain development and behavior”.

Authors:

Rochellys Diaz Heijtza,b,1, Shugui Wangc, Farhana Anuard, Yu Qiana,b, Britta Björkholmd, Annika Samuelssond, Martin L. Hibberdc, Hans Forssbergb,e, and Sven Petterssonc,d,1

Departments of aNeuroscience, and dMicrobiology, Cell and Tumor Biology, bStockholm Brain Institute, Karolinska Institutet, 171 77 Stockholm, Sweden ;

cGenome Institute of Singapore, 02-01 Genome 138672, Singapore ;

eDepartment of Women’s and Children’s Health, Karolinska Institutet, 171 76 Stockholm, Sweden

Source:
Genome Institute of Singapore
Karolinska Institute
Agency for Science, Technology and Research (A*STAR)