Embryonic stem cells are obtained from embryos and can be maintained in cell cultures as pluripotent stem cell lines with a capacity to differentiate into whole embryos. Studies have shown a four- to six-fold increase of CS/DS during the differentiation of murine embryonic stem cells to embroid bodies and to extra embryonic endodermal cells. The formation of embroid bodies and extra embryonic endodermal cells was accompanied by a two- and four-fold increase of IdoA, respectively 35, suggesting a role for IdoA. The biosynthetic genes DSE, DSEL and CHST14, coding for D4ST1, were expressed at all stages. CHST14 was also expressed in the extra embryonic endodermal cells. However, the detailed structure of CS/DS, as well as its functions, still needs to be determined.
