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.

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.

Aneuploidy is common and may be a natural occurrence in early human embryos. Selecting against embryos containing aneuploid cells for embryo transfer has been reported to increase clinical pregnancies per transfer in some studies, but not others. Some aneuploidy is due to misallocation of chromosomes during meiosis, in either the egg or sperm, but most aneuploidy is due to misallocation of chromosomes during mitoses after fertilization. Big questions are as follows: Why does this happen? How much aneuploidy in a preimplantation embryo is compatible with normal fetal development? Is aneuploidy increased by in vitro culture, and/or could it be prevented or corrected in the IVF lab?

Previous microarray analyses of RNAs from 8-cell (8C) human embryos revealed a lack of cell cycle checkpoints and overexpression of core circadian oscillators and cell cycle drivers relative to pluripotent human stem cells [human embryonic stem cells/induced pluripotent stem (hES/iPS)] and fibroblasts, suggesting growth factor independence during early cleavage stages. To explore this possibility, we queried our combined microarray database for expression of 487 growth factors and receptors. Fifty-one gene elements were overdetected on the 8C arrays relative to hES/iPS cells, including 14 detected at least 80-fold higher, which annotated to multiple pathways: six cytokine family (CSF1R, IL2RG, IL3RA, IL4, IL17B, IL23R), four transforming growth factor beta (TGFB) family (BMP6, BMP15, GDF9, ENG), one fibroblast growth factor (FGF) family [FGF14(FH4)], one epidermal growth factor member (GAB1), plus CD36, and CLEC10A. 8C-specific gene elements were enriched (73%) for reported circadian-controlled genes in mouse tissues. High-level detection of CSF1R, ENG, IL23R, and IL3RA specifically on the 8C arrays suggests the embryo plays an active role in blocking immune rejection and is poised for trophectoderm development; robust detection of NRG1, GAB1, -2, GRB7, and FGF14(FHF4) indicates novel roles in early development in addition to their known roles in later development. Forty-four gene elements were underdetected on the 8C arrays, including 11 at least 80-fold under the pluripotent cells: two cytokines (IFITM1, TNFRSF8), five TGFBs (BMP7, LEFTY1, LEFTY2, TDGF1, TDGF3), two FGFs (FGF2, FGF receptor 1), plus ING5, and WNT6. The microarray detection patterns suggest that hES/iPS cells exhibit suppressed circadian competence, underexpression of early differentiation markers, and more robust expression of generic pluripotency genes, in keeping with an artificial state of continual uncommitted cell division. In contrast, gene expression patterns of the 8C embryo suggest that it is an independent circadian rhythm-competent equivalence group poised to signal its environment, defend against maternal immune rejection, and begin the rapid commitment events of early embryogenesis.

Thanks to effective anti-HIV medications, deaths from acquired immunodeficiency disease (AIDS) have plummeted, although the incidence of new HIV infections has decreased little, approximately 36,000 annually in the USA. The CDC estimates 1.1 million persons, mostly men, are living with HIV in the USA, with approximately 14% unaware they are infected. Since the global blood supply is essentially free of HIV today, infected semen is fueling the pandemic (88% of new infections in the USA), with needle sharing among IV drug abusers (7% of new US infections) and female to male transmission (5% of new infections) accounting for the balance. In spite of the importance to disease prevention and strategies for safe conception, semen transmission of HIV is not well understood. Because anti-HIV therapy does not eliminate HIV from semen, the Centers for Disease Control (CDC) for the past 25 years has espoused condom use as the safest approach to prevent HIV transmission, as well as other sexually transmitted diseases. A few months ago, however, an MMWR was circulated by the CDC that suggested condomless sex might be safe if the HIV-infected partner’s medications achieved an undetectable viral load in his blood. This new opinion was based on reports by three teams of investigators cited in the MMWR: “All three studies observed no HIV transmission to the uninfected partner while the partner with HIV was virologically suppressed with ART.” Unfortunately, this CDC statement does not fully describe the data presented in the studies, and abandoning condom use puts uninfected partners, including women seeking to conceive, at risk for infection by HIV and other STDs.