Live imaging the specification and segregation of pluripotent epiblast and primitive endoderm lineages in the early mouse embryo
The first two lineages to differentiate from a pluripotent cell population during mammalian development are the extraembryonic trophectoderm (TE) and primitive endoderm (PrE). While the mechanisms of TE specification have been extensively studied, segregation of PrE and the pluripotent epiblast (EPI) has received comparatively little attention. To determine the precise sequence of events that leads to the specification and segregation of EPI and PrE lineages within the blastocyst stage embryo we are adopting a live imaging approach combined with the analysis of mouse mutants.
XEN cells: embryo-derived stem cells representing the primitive endoderm (PrE) lineage
We are interested in the mechanisms regulating the developmental potential of primitive endoderm-derived XEN cells. Current work exploits live imaging tools and mouse genetics to investigate XEN cell biology, including the transcription factors and signaling pathways regulating their self-renewal and directed differentiation.
ES cells, pluripotency and the reprogramming of differentiated cells.
Embryonic Stem (ES) cells are pluripotent cells derived from epiblast (EPI) of the mammalian balstocyst stage embryo that have the capacity to give rise to any fetal tissue. The ES genome can be modified at base pair resolution. These two properties of mouse ES cells hold the promise of human ES cells for tissue replacement therapies. However, tissue rejection in an outbred population like humans precludes such hopes whereby each individual would require "custom" ES cells.
In recent years, nuclear transfer technology has renewed interest in using ES cells for cell-based therapies. In the mouse, if somatic cell nuclei are transferred to enucleated oocytes, then development of the oocyte can be fostered until at least blastocyst stage. Blastocysts can then be used to derive ES cells with nuclei of somatic cell origin. This nuclear transfer technology circumvents the problem of tissue rejection in outbred human populations, but generates two ethical concerns, that this technique would require: (i) the isolation of human oocytes on a large scale, and (ii) that human embryogenesis be initiated in vitro and arrested at blastocyst stage. Recently, these two ethical problems have been circumvented with the finding that both mouse and human ES cells, like enucleated oocytes, can reprogram somatic nuclei into an ES-like state. A better understanding of the reprogramming capacity of ES cells could allow for the production of "custom" ES cells for any given individual.
In collaboration with Dr Paul Feinstein at Hunter College we are investigating the reprogramming capacity of mouse ES cells on somatic cell types. We are determining the rate of reprogramming in vivo and investigating whether somatically-derived ES cells are pluripotent.
