Rlim-Dependent and -Independent Pathways for X Chromosome Inactivation in Female ESCs

During female mouse embryogenesis, two forms of X chromosome inactivation (XCI) ensure dosage compensation from sex chromosomes. Beginning at the four-cell stage, imprinted XCI (iXCI) exclusively silences the paternal X (Xp), and this pattern is maintained in extraembryonic cell types. Epiblast cells, which give rise to the embryo proper, reactivate the Xp (XCR) and undergo a random form of XCI (rXCI) around implantation. Both iXCI and rXCI depend on the long non-coding RNA Xist. The ubiquitin ligase RLIM is required for iXCI in vivo and occupies a central role in current models of rXCI. Here, we demonstrate the existence of Rlim-dependent and Rlim-independent pathways for rXCI in differentiating female ESCs. Upon uncoupling these pathways, we find more efficient Rlim-independent XCI in ESCs cultured under physiological oxygen conditions. Our results revise current models of rXCI and suggest that caution must be taken when comparing XCI studies in ESCs and mice

F.A.R.O.G. FORUM, Vol. 6 No. 4

https://digitalcommons.library.umaine.edu/francoamericain_forum/1065/thumbnail.jp

On the impact of fundamentals, liquidity, and coordination on market stability

We develop a coordination game to model interactions between fundamentals and liquidity during unstable periods in financial markets. We then propose a flexible econometric framework for estimation of the model and analysis of its quantitative implications. The specific empirical application is carry trades in the yen-dollar market, including the turmoil of 1998. We find a generally very deep market, with low information disparities among agents. We observe occasional episodes of market fragility or turmoil withup by the escalator, down by the elevatorpatterns in prices. The key role of strategic behavior in the econometric model is also confirmed

RLIM is dispensable for X-chromosome inactivation in the mouse embryonic epiblast

In female mice, two forms of X-chromosome inactivation (XCI) ensure the selective silencing of female sex chromosomes during mouse embryogenesis. Beginning at the four-cell stage, imprinted XCI (iXCI) exclusively silences the paternal X chromosome. Later, around implantation, epiblast cells of the inner cell mass that give rise to the embryo reactivate the paternal X chromosome and undergo a random form of XCI (rXCI). Xist, a long non-coding RNA crucial for both forms of XCI, is activated by the ubiquitin ligase RLIM (also known as Rnf12). Although RLIM is required for triggering iXCI in mice, its importance for rXCI has been controversial. Here we show that RLIM levels are downregulated in embryonic cells undergoing rXCI. Using mouse genetics we demonstrate that female cells lacking RLIM from pre-implantation stages onwards show hallmarks of XCI, including Xist clouds and H3K27me3 foci, and have full embryogenic potential. These results provide evidence that RLIM is dispensable for rXCI, indicating that in mice an RLIM-independent mechanism activates Xist in the embryo proper

A Conversation Among the IAS-USA Board of Directors: Hot Topics and Emerging Data in HIV Research and Care.

The IAS-USA volunteer Board of Directors met in October 2016 for its annual meeting. For the second year, the Board conducted a live, hour-long, interactive, roundtable webinar covering current questions and issues in HIV research, prevention, and care. Important highlights from the Board's discussion, which was moderated by Paul A. Volberding, MD, are included below. Members of the IAS-USA volunteer Board of Directors are Constance A. Benson, MD; Judith S. Currier, MD; Carlos del Rio, MD; Joel E. Gallant, MD, MPH; Roy M. Gulick, MD, MPH; Jeanne M. Marrazzo, MD, MPH; Douglas D. Richman, MD; Michael S. Saag, MD; Robert T. Schooley, MD; and Paul A. Volberding, MD

A Conversation Among the IAS-USA Board of Directors: Hot Topics and Emerging Data in HIV Research and Care.

The IAS-USA volunteer Board of Directors met in October 2016 for its annual meeting. For the second year, the Board conducted a live, hour-long, interactive, roundtable webinar covering current questions and issues in HIV research, prevention, and care. Important highlights from the Board's discussion, which was moderated by Paul A. Volberding, MD, are included below. Members of the IAS-USA volunteer Board of Directors are Constance A. Benson, MD; Judith S. Currier, MD; Carlos del Rio, MD; Joel E. Gallant, MD, MPH; Roy M. Gulick, MD, MPH; Jeanne M. Marrazzo, MD, MPH; Douglas D. Richman, MD; Michael S. Saag, MD; Robert T. Schooley, MD; and Paul A. Volberding, MD