Identification of molecular markers that are expressed in discrete anterior-posterior domains of the endoderm from the gastrula stage to mid-gestation.

Little is known about how the endoderm germ layer is patterned along the anterior-posterior (A-P) axis before the formation of a gut tube (embryonic day [e] 7.5-8.5 in mouse), largely due to a paucity of molecular markers of endoderm.

Differential expression of Sonic hedgehog along the anterior-posterior axis regulates patterning of pharyngeal pouch endoderm and pharyngeal endoderm-derived organs.

Previous studies have implicated Sonic hedgehog (Shh) as an important regulator of pharyngeal region development. Here we show that Shh is differentially expressed within the pharyngeal endoderm along the anterior-posterior axis. In Shh-/- mutants, the pharyngeal pouches and arches formed by E9.

Ontogeny and regulation of IL-7-expressing thymic epithelial cells.

Epithelial cells in the thymus produce IL-7, an essential cytokine that promotes the survival, differentiation, and proliferation of thymocytes. We identified IL-7-expressing thymic epithelial cells (TECs) throughout ontogeny and in the adult mouse thymus by in situ hybridization analysis. IL-7 expression is initiated in the thymic fated domain of the early primordium by embryonic day 11.

In vivo and in vitro assays of thymic organogenesis.

We describe two complementary methods for the study of early thymus organogenesis in the mouse. The first is an in vitro technique for lineage analysis, where a chosen population of cells within the mouse embryo is labeled with a fluorescent cell tracker dye. The embryos are then transferred to whole embryo culture for a defined period, after which time the location of the labeled cells is determined with respect to the developing thymus.

New serum-free in vitro culture technique for midgestation mouse embryos.

Current in vitro culture methods for mouse embryos are critically dependent on specially prepared rodent serum. Rodent serum requires careful preparation and stringent assessment of serum quality, while commercially available whole embryo culture serum is expensive and shows considerable lot variability. Thus, preparation and testing of suitable serum represents a considerable investment of time and resources, particularly for laboratories with only short-term embryo culture requirements.