Summary Currently there are no approved vaccines or specific therapies to prevent or treat Zika virus (ZIKV) infection. We interrogated a library of FDA-approved drugs for their ability to block infection of human HuH-7 cells by a newly isolated ZIKV strain (ZIKV MEX_I_7). More than 20 out of 774 tested compounds decreased ZIKV infection in our in vitro screening assay. Selected compounds were further validated for inhibition of ZIKV infection in human cervical, placental and neural stem cell lines, as well as primary human amnion cells. Established anti-flaviviral drugs (e.g., bortezomib and mycophenolic acid) and others that had no previously known anti-viral activity (e.g., daptomycin) were identified as inhibitors of ZIKV infection. Several drugs reduced ZIKV infection across multiple cell types. This study identifies drugs that could be tested in clinical studies of ZIKV infection and provides a resource of small molecules to study ZIKV pathogenesis.

SummaryZika virus (ZIKV) infection causes microcephaly in a subset of infants born to infected pregnant mothers. It is unknown whether human individual differences contribute to differential susceptibility of ZIKV-related neuropathology. Here, we use an Asian-lineage ZIKV strain, isolated from the 2015 Mexican outbreak (Mex1-7), to infect primary human neural stem cells (hNSCs) originally derived from three individual fetal brains. All three strains of hNSCs exhibited similar rates of Mex1-7 infection and reduced proliferation. However, Mex1-7 decreased neuronal differentiation in only two of the three stem cell strains. Correspondingly, ZIKA-mediated transcriptome alterations were similar in these two strains but significantly different from that of the third strain with no ZIKV-induced neuronal reduction. This study thus confirms that an Asian-lineage ZIKV strain infects primary hNSCs and demonstrates a cell-strain-dependent response of hNSCs to ZIKV infection.

DNA base editors have enabled genome editing without generating DNA double strand breaks. The applications of this technology have been reported in a variety of animal and plant systems, however, their editing specificity in human stem cells has not been studied by unbiased genome-wide analysis. Here we investigate the fidelity of cytidine deaminase-mediated base editing in human induced pluripotent stem cells (iPSCs) by whole genome sequencing after sustained or transient base editor expression. While base-edited iPSC clones without significant off-target modifications are identified, this study also reveals the potential of APOBEC-based base editors in inducing unintended point mutations outside of likely in silico-predicted CRISPR-Cas9 off-targets. The majority of the off-target mutations are C:G->T:A transitions or C:G->G:C transversions enriched for the APOBEC mutagenesis signature. These results demonstrate that cytosine base editor-mediated editing may result in unintended genetic modifications with distinct patterns from that of the conventional CRISPR-Cas nucleases.

A major aspect of mammalian aging is the decline in functional competence of many self-renewing cell types, including adult-born neuronal precursors. Since age-related senescence of self-renewal occurs simultaneously with chronic up-regulation of the p38MAPKalpha (p38α) signaling pathway, we used the dominant negative mouse model for attenuated p38α activity (DN-p38αAF/+ ) in which Thr180 and Tyr182 are mutated (T→A/Y→F) to prevent phosphorylation activation (DN-p38αAF/+) and kinase activity. As a result, aged DN-p38αAF/+ mice are resistant to age-dependent decline in proliferation and regeneration of several peripheral tissue progenitors when compared to wild-type littermates. Aging is the major risk factor for non-inherited forms of Alzheimer’s disease (AD); environmental and genetic risk factors that accelerate the senescence phenotype are thought to contribute to an individual’s relative risk. In the present study, we evaluated aged DN-p38αAF/+ and wildtype littermates in a series of behavioral paradigms to test if p38α mutant mice exhibit altered baseline abnormalities in neurological reflexes, locomotion, anxiety-like behavior, and age-dependent cognitive decline. While aged DN-p38αAF/+ and wildtype littermates appear equal in all tested baseline neurological and behavioral parameters, DN-p38αAF/+ exhibit superior context discrimination fear conditioning. Context discrimination is a cognitive task that is supported by proliferation and differentiation of adult-born neurons in the dentate gyrus of the hippocampus. Consistent with enhanced context discrimination in aged DN-p38αAF/+, we discovered enhanced production of adult-born neurons in the dentate gyrus of DN-p38αAF/+ mice compared to wildtype littermates. Our findings support the notion that p38α inhibition has therapeutic utility in aging diseases that affect cognition, such as AD.

SummaryChronic alcohol abuse results in alcohol-related neurodegeneration, and critical gaps in our knowledge hinder therapeutic development. Neural stem cells (NSCs) are a subpopulation of cells within the adult brain that contribute to brain maintenance and recovery. While it is known that alcohol alters NSCs, little is known about how NSC response to alcohol is related to sex, brain region, and stage of differentiation. Understanding these relationships will aid in therapeutic development. Here, we used an inducible transgenic mouse model to track the stages of differentiation of adult endogenous NSCs and observed distinct NSC behaviors in three brain regions (subventricular zone, subgranular zone, and tanycyte layer) after long-term alcohol consumption. Particularly, chronic alcohol consumption profoundly affected the survival of NSCs in the subventricular zone and altered NSC differentiation in all three regions. Significant differences between male and female mice were further discovered.