Clec12a controls colitis by tempering inflammation and restricting expansion of specific commensals.

Microbiota composition regulates colitis severity, yet the innate immune mechanisms that control commensal communities and prevent disease remain unclear. We show that the innate immune receptor, Clec12a, impacts colitis severity by regulating microbiota composition. Transplantation of microbiota from a Clec12a animal is sufficient to worsen colitis in wild-type mice.

Clec12a tempers inflammation while restricting expansion of a colitogenic commensal.

Regulation of the microbiota is critical to intestinal health yet the mechanisms employed by innate immunity remain unclear. Here we show that mice deficient in the C-Type-lectin receptor, Clec12a developed severe colitis, which was dependent on the microbiota. Fecal-microbiota-transplantation (FMT) studies into germfree mice revealed a colitogenic microbiota formed within Clec12a mice that was marked by expansion of the gram-positive organism, .

BefA, a microbiota-secreted membrane disrupter, disseminates to the pancreas and increases β cell mass.

Microbiome dysbiosis is a feature of diabetes, but how microbial products influence insulin production is poorly understood. We report the mechanism of BefA, a microbiome-derived protein that increases proliferation of insulin-producing β cells during development in gnotobiotic zebrafish and mice. BefA disseminates systemically by multiple anatomic routes to act directly on pancreatic islets.

CD11c+ myeloid cell exosomes reduce intestinal inflammation during colitis.

Intercellular communication is critical for homeostasis in mammalian systems, including the gastrointestinal (GI) tract. Exosomes are nanoscale lipid extracellular vesicles that mediate communication between many cell types. Notably, the roles of immune cell exosomes in regulating GI homeostasis and inflammation are largely uncharacterized.

From bugs to β cells.

Do ancient microbial irritants offer early life protection against diabetes?

SnapShot: Microbiota effects on host physiology.

Microbes can play both pathogenic and commensal roles, and it is common to label them as either detrimental or beneficial. However, the lines between good and bad can be blurred. This graphical summary attempts to illustrate the complexity of host-microbe interactions, with outcomes for human health being highly context specific.

A conserved bacterial protein induces pancreatic beta cell expansion during zebrafish development.

Resident microbes play important roles in the development of the gastrointestinal tract, but their influence on other digestive organs is less well explored. Using the gnotobiotic zebrafish, we discovered that the normal expansion of the pancreatic β cell population during early larval development requires the intestinal microbiota and that specific bacterial members can restore normal β cell numbers. These bacteria share a gene that encodes a previously undescribed protein, named herein BefA (β Cell Expansion Factor A), which is sufficient to induce β cell proliferation in developing zebrafish larvae.