Tag: Kristi Hamilton

Novel Bacterial Protein AimA Promotes Mutualism by Increasing Commensal Fitness and Reducing Inflammation in the Host

Presenter(s): Lila Kaye − Biology, Emphasis In Cellular And Mollecular

Faculty Mentor(s): Karen Guillemin, Kristi Hamilton

Poster 50

Research Area: Microbiology

Funding: SPUR 2016, VPRI 2017, Meta, NIH

The microbiota of the gastrointestinal tract is critical for the development and regulation of the host immune system. Some bacterial genera are associated with health and homeostasis, while others have been linked to inflammation and disease. There have been many studies in recent literature investigating the potential role of commensal microbes in autoimmune and gastrointestinal diseases, both preventative and pathogenic. Much less is known, however, about how interactions with the immune system benefit resident microbes. Here I used the zebrafish, Danio rerio, as a powerful gnotobiotic model for investigating host-microbe symbiosis. I investigated the novel immunoregulatory protein aimA, produced by the zebrafish commensal Aeromonas, and show that it facilitates mutualism with the host by reducing gastrointestinal inflammation and increasing bacterial intestinal colonization in both monoassociations and co-inoculation with pro-inflammatory species Vibrio. Using GFP-tagged neutrophils as a reporter for inflammation, I showed that a deletion mutant lacking the gene for AimA (∆aimA) is unable to regulate host immune response and cannot colonize the gut as robustly. Inoculation into immunocompromised MyD88-/-hosts having decreased intestinal inflammation rescues the colonization defect suffered in the absence of aimA, demonstrating reciprocity between control of the host biology and control of the resident bacterial biology. Identification of bacterial products involved in establishing a healthy symbiosis with the host is crucial for understanding how commensal communities are assembled and maintained.

Inflammatory Phenotypes Of Zebrafish Enteric Nervous System Mutants

Presenter(s): Lillian Carroll − Biology

Faculty Mentor(s): Judith Eisen, Kristi Hamilton

Oral Session 4S

Research Area: Natural Science

Funding: OURS Program

Intestinal health depends on the microbial community within the dynamic intestinal environment. The enteric nervous system (ENS) innervates the intestine and modulates the microbial community composition. ENS reduction causes Hirschsprung disease (HSCR), resulting in intestinal dysmotility. Many HSCR patients develop potentially life-threatening intestinal inflammation. HSCR is genetically complex, with multiple HSCR genetic loci. The zebrafish is an excellent model in which to study the relationship between inflammation and genes linked to HSCR. Zebrafish with a mutation in the HSCR gene, sox10, have fewer enteric neurons, increased intestinal epithelial cell proliferation, and develop microbiota-dependent intestinal inflammation. Zebrafish with a mutation in another HSCR gene, ret, also have fewer ENS neurons but do not exhibit increased intestinal inflammation. sox10 acts in neural crest cells that form the ENS and ret acts within ENS cells, thus, I hypothesized that the intestinal phenotype of sox10;ret double mutants would be similar to the phenotype of sox10 mutants. To test this hypothesis, I analyzed the phenotypes of double mutants. I used PCR to identify mutants and quantified inflammation by counting intestinal neutrophils and recently-proliferated intestinal epithelial cells, and by determining the intestinal bacterial abundance. Surprisingly, and contrary to my hypothesis, sox10;ret double mutants did not exhibit increased intestinal inflammation or cell proliferation compared to wild-types. These results prompt me to reconsider the potential interactions

of the mutated genes, which will provide insights into the role of the ENS as a crucial regulator of the intestinal microbial community and its function in the maintenance of intestinal health.

Intestinal Phenotypes of Zebrafish Enteric Nervous System Double Mutants

Presenter(s): Lilly Carroll

Faculty Mentor(s): Judith Eisen & Kristi Hamilton

Oral Session 4 S

The enteric nervous system (ENS) innervates the intestine and regulates the dynamic intestinal environment. ENS reduction causes Hirschsprung disease (HSCR), a genetically complex disease that results in intestinal dysmotility and, in many patients, intestinal inflammation. The zebrafish is an excellent model in which to study the relationship between inflammation and genes linked to HSCR. Zebrafish with a mutation in one HSCR gene, sox10, have fewer enteric neurons and develop microbiota-dependent intestinal inflammation. Zebrafish with a mutation in another HSCR gene, ret, also have fewer ENS neurons but do not exhibit increased intestinal inflammation. To investigate the opposing intestinal phenotypes of sox10 and ret mutants, I analyzed intestinal phenotypes of sox10;ret double mutants. Because sox10 acts in neural crest cells that form the ENS and ret acts later, within ENS cells, I hypothesized that intestinal inflammatory phenotypes of sox10;ret double mutants would resemble those of sox10 mutants. To test this hypothesis, I quantified intestinal inflammation in sox10;ret double mutants by counting intestinal neutrophils. Surprisingly, I observed a wild-type (WT) neutrophil abundance phenotype in sox10;ret mutants. This result led me to investigate intestinal enterochromaffin cells, which produce serotonin and express ret but not sox10. I hypothesized that sox10;ret double mutants would exhibit the same decreased enterochromaffin cell phenotype as ret mutants. However, sox10;ret mutants had more enterochromaffin cells that ret mutants and were similar to WT. This result prompts further exploration of the potential interactions of the mutated genes for insights into the role of the ENS in maintenance of intestinal health.