An Nkx2-5/Bmp2/Smad1 negative feedback loop controls heart progenitor specification and proliferation.

During heart development the second heart field (SHF) provides progenitor cells for most cardiomyocytes and expresses the homeodomain factor Nkx2-5. We now show that feedback repression of Bmp2/Smad1 signaling by Nkx2-5 critically regulates SHF proliferation and outflow tract (OFT) morphology. In the cardiac fields of Nkx2-5 mutants, genes controlling cardiac specification (including Bmp2) and maintenance of the progenitor state were upregulated, leading initially to progenitor overspecification, but subsequently to failed SHF proliferation and OFT truncation.

Mucispirillum schaedleri gen. nov., sp. nov., a spiral-shaped bacterium colonizing the mucus layer of the gastrointestinal tract of laboratory rodents.

The mammalian gastrointestinal tract is covered by a layer of mucus that can harbour a range of bacterial species specifically adapted to colonize this ecological niche. Examination of 110 bacterial isolates cultivated from the gastrointestinal tract of 23 mice revealed the presence of a subgroup of 30 isolates that did not correspond genetically with genera commonly associated with this site, i.e.

Detection of Helicobacter colonization of the murine lower bowel by genus-specific PCR-denaturing gradient gel electrophoresis.

Helicobacter genus-specific PCR and denaturing gradient gel electrophoresis can detect and speciate the helicobacters that colonize the lower bowel of laboratory mice. The method's sensitivity is comparable to that of species-specific PCR and may detect unnamed Helicobacter species. This approach should prove useful for commercial and research murine facilities.