These folds, consisting of extra-embryonic ectoderm and extra-embryonic mesoderm, rise up and fuse dorsally, enclosing the embryo in a double-lined, fluid-filled chamber known as the amniotic cavity.
Finally, by comparing the three related but dissimilar cell lines, we are able to refine the list of markers that distinguish between different subtypes of endoderm including those that distinguish DE from VE. Endoderm both embryonic and extra-embryonic has been shown in various model systems to play an inductive role in the differentiation of mesodermal and ectodermal tissues that adjoin it.
Both embryonic and extra-embryonic regions in mutant embryos are smaller than controls, suggesting abnormal embryogenesis (Figure 1B1 and 1B2).
Endoderm, both embryonic and extra-embryonic plays important morphogenetic functions in the mouse and other vertebrate embryos.
However, further post-implantation development requires PTBP1 and stalls in homozygous null animals with a phenotype of dramatically reduced size and aberration in embryonic and extra-embryonic structures.
Whole-mount in situ hybridization of mouse embryos between E7.5 and E9.5 revealed abundant expression in most embryonic and extra-embryonic tissues.
Deletion of Phlda2 causes placentomegaly and mice that lack Hand1 die at embryonic day 8.5 from placental and extra-embryonic abnormalities [22], [26].
Until the eight-cell stage of mouse development, blastomeres are totipotent and retain the ability to contribute to all embryonic and extra-embryonic cell lineages [26], [27].
Taken together, our in situ hybridization experiments indicate abundant expression of Sp2 in most embryonic and extra-embryonic tissues during development.
By providing a clearer picture of endodermal subtypes, these studies should assist the development of experimental protocols that require a distinction between embryonic and extra-embryonic lineages.
