Human embryonic stem cells

xii, 280 p.; ill.; 24 cm

Evidence that human blastomere cleavage is under unique cell cycle control

To understand the molecular pathways that control early human embryo development. Improved methods of linear amplification of mRNAs and whole human genome microarray analyses were utilized to characterize gene expression in normal appearing 8-Cell human embryos, in comparison with published microarrays of human fibroblasts and pluripotent stem cells. Many genes involved in circadian rhythm and cell division were over-expressed in the 8-Cells. The cell cycle checkpoints, RB and WEE1, were silent on the 8-Cell arrays, whereas the recently described tumor suppressor, UHRF2, was up-regulated > 10-fold, and the proto-oncogene, MYC, and the core element of circadian rhythm, CLOCK, were elevated up to > 50-fold on the 8-Cell arrays. The canonical G1 and G2 cell cycle checkpoints are not active in totipotent human blastomeres, perhaps replaced by UHRF2, MYC, and intracellular circadian pathways, which may play important roles in early human development

Genome-wide microarray evidence that 8-cell human blastomeres over-express cell cycle drivers and under-express checkpoints

Purpose To understand cell cycle controls in the 8-Cell human blastomere. Methods Data from whole human genome (43,377 elements) microarray analyses of RNAs from normal 8-Cell human embryos were compiled with published microarrays of RNAs from human fibroblasts, before and after induced pluripotency, and embryonic stem cells. A sub database of 3,803 genes identified by high throughput RNA knock-down studies, plus genes that oscillate in human cells, was analyzed. Results Thirty-five genes over-detected at least 7-fold specifically on the 8-Cell arrays were enriched for cell cycle drivers and for proteins that stabilize chromosome cohesion and spindle attachment and limit DNA and centrosome replication to once per cycle. Conclusions These results indicate that 8-cell human blastomere cleavage is guided by cyclic over-expression of key proteins, rather than canonical checkpoints, leading to rapidly increasing gene copy number and a susceptibility to chromosome and cytokinesis mishaps, well-noted characteristics of preimplantation human embryos

Rapid communication: somatic cell nuclear transfer in humans: pronuclear and early embryonic development

ABSTRACT Human therapeutic cloning requires the reprogramming of a somatic cell by nuclear transfer to generate autologous totipotent stem cells. We have parthenogenetically activated 22 human eggs and also performed nuclear transfer in 17 metaphase II eggs. Cleavage beyond the eight-cell stage was obtained in the parthenogenetic-activated eggs, and blastocoele cavities were observed in six. Three somatic cell-derived embryos developed beyond the pronuclear stage up to the six-cell stage. The ability to create autologous embryos represents the first step towards generating immune-compatible stem cells that could be used to overcome the problem of immune rejection in regenerative medicine

Overseeing research on therapeutic cloning: a private ethics board responds to its critics

Advanced Cell Technology's Ethics Advisory Board has been called window dressing for a corporate marketing plan. But the scientists and managers have paid attention, and the lawyers have gone along