%0 Journal Article
%T The States of Pluripotency: Pluripotent Lineage Development in the Embryo and in the Dish
%A Joy Rathjen
%J ISRN Stem Cells
%D 2014
%R 10.1155/2014/208067
%X The pluripotent cell lineage of the embryo comprises a series of temporally and functionally distinct intermediary cell states, the epiblast precursor cell of the newly formed blastocyst, the epiblast population of the inner cell mass, and the early and late epiblast of the postimplantation embryo, referred to here as early and late primitive ectoderm. Pluripotent cell populations representative of the embryonic populations can be formed in culture. Although multiple pluripotent cell states are now recognised, little is known about the signals and pathways that progress cells from the epiblast precursor cell to the late primitive ectoderm in the embryo or in culture. The characterisation of cell states is most advanced in mouse where conditions for culturing distinct pluripotent cell states are well established and embryonic material is accessible. This review will focus on the pluripotent cell states present during embryonic development in the mouse and what is known of the mechanisms that regulate the progression of the lineage from the epiblast precursor cell and the ground state of pluripotency to the late primitive ectoderm present immediately prior to cell differentiation. 1. Introduction Establishment and development of the pluripotent cell lineage in the mouse embryo are a progressive process characterised by the sequential formation of a series of temporally and functionally distinct intermediary cell states. Cells fated to form the pluripotent lineage can be identified in the interior of the compacted morula of the mouse embryo by day 3, encapsulated within cells destined to establish the trophectoderm. These cells establish the inner cell mass (ICM) of the blastocyst, which on day 3.5 comprises genetically discrete populations of epiblast precursor cells and primitive endoderm precursor cells. By 4.5 days post coitum (d.p.c.) these populations have segregated into spatially distinct regions of the ICM and cell identity has been fixed, forming the pluripotent epiblast and the extraembryonic primitive endoderm lineage (also known as the hypoblast). The epiblast proliferates rapidly and forms a psuedostratified epithelium of epiblast that has been designated primitive ectoderm. Primitive ectoderm can be distinguished from the preceding epiblast by morphology, gene expression, and differentiation potential. Analysis of the mouse embryo has revealed at least four identifiable pluripotent cell populations, or states, that comprise the pluripotent lineage¡ªthe epiblast precursor cell, the epiblast of the ICM, and the early and late epiblasts of the
%U http://www.hindawi.com/journals/isrn.stem.cells/2014/208067/