Showing papers by "Richard L. Gardner published in 2003"

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

Abstract: 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. Consequently, we developed ES cell lines derived from (NOD x 129)F1 x 129 backcross 1 mice, which were intercrossed to select for homozygosity of particular regions of NOD genome known to contain disease loci.

The basis and significance of pre-patterning in mammals.

Abstract: 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. It also maps too variably on the blastocyst to play a causal role in early patterning. The zygote has been found transiently to exhibit bilateral symmetry before regaining an essentially spherical shape prior to first cleavage. Marking experiments indicate that the plane of bilateral symmetry of the blastocyst is aligned with, and the plane of first cleavage is typically orthogonal to, the zygote's bilateral plane. The bilateral symmetry of the zygote bears no consistent relationship either to the point of sperm entry or to the distribution of the pronuclei, and may therefore be a manifestation of intrinsic organization of the egg. Finally, the two-cell blastomere inheriting the sperm entry point has not been found to differ consistently in fate from the one that does not.

Is the plane of first cleavage related to the point of sperm entry in the mouse

Abstract: The notion that pattern formation cannot depend on cues that are already present in the zygote has dominated thinking about early development in mammals for more than 3 decades. However, recent studies in the mouse have rendered this notion untenable. The first pertinent study provided evidence that the axis of bilateral symmetry of the early blastocyst was aligned with the animal–vegetal axis of the zygote (Gardner, 1997). Subsequently, it was found that the embryonic–abembryonic axis and equatorial plane of the blastocyst were normally related to the plane of first cleavage, being approximately orthogonal and parallel to this plane respectively (Gardner, 2001; Piotrowska and Zernicka-Goetz, 2001; Piotrowska et al., 2001). Collectively, these findings argue that both axes of the blastocyst are already specified before cleavage in the mouse, and therefore raise the question whether the asymmetries necessary for their specification are intrinsic to the egg or imposed on it by the fertilizing spermatozoon. Using phytohaemagglutinin (PHA)-treated fluorescent microspheres (beads) as markers, Piotrowska and Zernicka-Goetz (2001) claim to have established a patterning role for the spermatozoa by demonstrating that the sperm entry point (SEP) consistently maps to the plane of first cleavage.