High-throughput screening (HTS) of chemical libraries has become a critical tool in basic biology and drug discovery. However, its implementation and the adaptation of high-content assays to human embryonic stem cells (hESCs) have been hampered by multiple technical challenges. Here we present a strategy to adapt hESCs to HTS conditions, resulting in an assay suitable for the discovery of small molecules that drive hESC self-renewal or differentiation. Use of this new assay has led to the identification of several marketed drugs and natural compounds promoting short-term hESC maintenance and compounds directing early lineage choice during differentiation. Global gene expression analysis upon drug treatment defines known and novel pathways correlated to hESC self-renewal and differentiation. Our results demonstrate feasibility of hESC-based HTS and enhance the repertoire of chemical compounds for manipulating hESC fate. The availability of high-content assays should accelerate progress in basic and translational hESC biology.
The bioterror threat of a smallpox outbreak in an unvaccinated population has mobilized efforts to develop new antipoxviral agents. By screening a library of known drugs, we identified 13 compounds that inhibited vaccinia virus replication at noncytotoxic doses. The anticancer drug mitoxantrone is unique among the inhibitors identified in that it has no apparent impact on viral gene expression. Rather, it blocks processing of viral structural proteins and assembly of mature progeny virions. The isolation of mitoxantrone-resistant vaccinia strains underscores that a viral protein is the likely target of the drug. Whole-genome sequencing of mitoxantrone-resistant viruses pinpointed missense mutations in the N-terminal domain of vaccinia DNA ligase. Despite its favorable activity in cell culture, mitoxantrone administered intraperitoneally at the maximum tolerated dose failed to protect mice against a lethal intranasal infection with vaccinia virus.Poxviruses have been at the forefront of advances in medicine for 200 years, from Jenner's paper on the efficacy of vaccination against smallpox in 1798 to the successful use of vaccinia virus to eradicate human smallpox disease, as proclaimed by the World Health Organization in 1977. Throughout the 1990s, the scientific community debated the proposed destruction of the last known stocks of smallpox virus (24, 31). Hanging over this discussion was the fear that undeclared stocks of smallpox could be used as a bioterror weapon against an unvaccinated population. The urgency of this threat was amplified by the terrorist attacks of 2001, followed by the dissemination of anthrax via the postal service. The outbreak of human monkeypox infections in the United States in 2003 further highlighted the risks of reemergence of human poxvirus disease.Public health and research efforts have been mobilized accordingly to (i) exploit a modified live smallpox vaccine that maintains efficacy while minimizing complications, (ii) pursue alternatives to live vaccination for smallpox prophylaxis, and (iii) discover and bring forward for FDA approval new antipoxviral drugs. Two very different clinical scenarios present different challenges for drug therapy. Prophylaxis of a low-risk population in the event of a threat or actual outbreak mandates an orally available drug with minimal side effects. In contrast, the treatment of confirmed cases of smallpox (which can have a Ն30% fatality rate) need not be hindered by concerns about route of administration and non-life-threatening side effects. The goal is to have at least two approved antipoxviral drugs that act on different molecular targets.Although many inhibitors of poxvirus replication in culture or animal models have been described previously (50), the initial efforts post-2001 focused on the nucleoside analog cidofovir, an inhibitor of the viral DNA polymerase (28), which was already FDA approved for treatment of cytomegalovirus retinitis. Cidofovir was found to be effective in animal models of orthopoxvirus infection (37,50,53). However,...
We report a 3-component reaction between N-benzyl ketimines, [1.1.1]propellane, and pinacol boronates to generate benzylamine bicyclo[1.1.1]pentane (BCP) pinacol boronates. These structures are analogous to highly sought after diarylmethanamine cores, which...
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