On the fate of primordial germ cells injected into early mouse embryos.

Primordial germ cells (PGCs) are the founder cells of the germline. Via gametogenesis and fertilisation this lineage generates a new embryo in the next generation. PGCs are also the cell of origin of multilineage teratocarcinomas.

Normal bias in the direction of fetal rotation depends on blastomere composition during early cleavage in the mouse.

Interest in establishing the basis of left/right asymmetry during embryogenesis has burgeoned in recent years. Relevant studies in mammals, focused largely on the mouse, have revealed involvement of a variety of genes that are common to the process in other animals. In the mouse, lateral differences in gene expression are first evident late in gastrulation when directional rotation of nodal cilia has been implicated in effecting the normally very strong bias in handedness.

Embryonic stem cell-derived tissues are immunogenic but their inherent immune privilege promotes the induction of tolerance.

Although human embryonic stem (ES) cells may one day provide a renewable source of tissues for cell replacement therapy (CRT), histoincompatibility remains a significant barrier to their clinical application. Current estimates suggest that surprisingly few cell lines may be required to facilitate rudimentary tissue matching. Nevertheless, the degree of disparity between donor and recipient that may prove acceptable, and the extent of matching that is therefore required, remain unknown.

Stem cells and regenerative medicine: principles, prospects and problems.

Stem cells have been used routinely for more than three decades to repair tissues and organs damaged by injury or disease, most notably haematopoietic stem cells taken from bone marrow, umbilical cord or, increasingly, from peripheral blood. Other examples, such as grafts of skin to treat severe burns, entail transplantation of stem cells within organized tissue rather than following isolation. The prospect of exploiting stem cells more widely in regenerative medicine was encouraged both by the development of human assisted conception and growing evidence that various adult cells retained greater versatility than had been suspected hitherto.

New cell lines from mouse epiblast share defining features with human embryonic stem cells.

The application of human embryonic stem (ES) cells in medicine and biology has an inherent reliance on understanding the starting cell population. Human ES cells differ from mouse ES cells and the specific embryonic origin of both cell types is unclear. Previous work suggested that mouse ES cells could only be obtained from the embryo before implantation in the uterus.

The case for prepatterning in the mouse.

In studies from several laboratories using a variety of different techniques, features of the zygote and two-cell conceptus have been found to map nonrandomly on the blastocyst with respect to both its axis of polarity and bilateral plane. This is not what would be expected if, as is widely believed, early patterning depends entirely on positional relationships and interactions among the progeny of blastomeres that are equipotential until at least the eight-cell stage. Rather, the implication of these findings is that prepatterning is a normal facet of development in mammals, just as it is in most other metazoa.

Experimental analysis of the transdifferentiation of visceral to parietal endoderm in the mouse.

The visceral endoderm (VE) of isolated extraembryonic regions (ExEmbs) of 7 days postcoitum (dpc) prestreak mouse conceptuses have been shown to convert readily to parietal endoderm (PE). The present study addresses the following three unanswered questions. On what does conversion depend, how rapidly does it occur, and is it an enduring general property of a residual small population of relatively immature cells? In situ hybridization reveals that change in cell state occurs within 2 days of culture.

Imprinted X-inactivation in extra-embryonic endoderm cell lines from mouse blastocysts.

The extra-embryonic endoderm lineage plays a major role in the nutritive support of the embryo and is required for several inductive events, such as anterior patterning and blood island formation. Blastocyst-derived embryonic stem (ES) and trophoblast stem (TS) cell lines provide good models with which to study the development of the epiblast and trophoblast lineages, respectively. We describe the derivation and characterization of cell lines that are representative of the third lineage of the blastocyst -extra-embryonic endoderm.

The basis and significance of pre-patterning in mammals.

The second polar body (Pb) provides an enduring marker of the animal pole of the zygote, thereby revealing that the axis of bilateral symmetry of the early blastocyst is aligned with the zygote's animal-vegetal axis. That this relationship is biologically significant appeared likely when subsequent studies showed that the equator of the blastocyst tended to correspond with the plane of first cleavage. However, this cleavage plane varies both with respect to the position of the second Pb and to the distribution of components of the fertilizing sperm that continue to mark the point where it entered the egg.

The derivation of highly germline-competent embryonic stem cells containing NOD-derived genome.

It would be extremely advantageous to the analysis of disease mechanisms in the spontaneous mouse model of type 1 diabetes, the nonobese diabetic (NOD) strain, if genes in this strain could be modified in vivo using embryonic stem (ES) cells and homologous recombination. However, a NOD ES cell line with adequate germline transmission has not yet been reported. We report the development of highly germline-competent ES cell lines from the F1 hybrid of NOD and 129 for use in NOD gene targeting.

Inhibition of trophoblast stem cell potential in chorionic ectoderm coincides with occlusion of the ectoplacental cavity in the mouse.

At the blastocyst stage of pre-implantation mouse development, close contact of polar trophectoderm with the inner cell mass (ICM) promotes proliferation of undifferentiated diploid trophoblast. However, ICM/polar trophectoderm intimacy is not maintained during post-implantation development, raising the question of how growth of undifferentiated trophoblast is controlled during this time. The search for the cellular basis of trophoblast proliferation in post-implantation development was addressed with an in vitro spatial and temporal analysis of fibroblast growth factor 4-dependent trophoblast stem cell potential.

Trophectoderm growth and bilateral symmetry of the blastocyst in the mouse.

Background: The present study was undertaken to ascertain whether the polarized flow of cells from polar to mural trophectoderm is related to the axis of bilateral symmetry of the blastocyst in the mouse, and whether trophectoderm cells can initiate new cycles once they have left the polar region.

Methods And Results: Two different approaches were used to investigate the relationship of polar to mural flow of trophectoderm cells to the bilateral axis. One was to mark peripheral polar trophectoderm cells at one or both ends of the bilateral axis in early blastocysts and examine the distribution of their clonal descendants after further growth in culture.