The transcription factor SRY (sex-determining region)-box 2 (SOX2) is an important functional marker of neural precursor cells (NPCs) and plays a critical role in self-renewal and neuronal differentiation; however, the molecular mechanisms underlying its functions are poorly understood. Using human embryonic stem cellderived NPCs to model neurogenesis, we found that SOX2 is required to maintain optimal levels of LIN28, a well-characterized suppressor of let-7 microRNA biogenesis. Exogenous LIN28 expression rescued the NPC proliferation deficit, as well as the early but not the late stages of the neurogenic deficit associated with the loss of SOX2. We found that SOX2 binds to a proximal site in the LIN28 promoter region and regulates LIN28 promoter acetylation, likely through interactions with the histone acetyltransferase complex. Misexpression of let-7 microRNAs in NPCs reduced proliferation and inhibited neuronal differentiation, phenocopying the loss of SOX2. In particular, we identified let-7i as a novel and potent inhibitor of neuronal differentiation that targets MASH1 and NGN1, two well-characterized proneural genes. In conclusion, we discovered the SOX2-LIN28/let-7 pathway as a unique molecular mechanism governing NPC proliferation and neurogenic potential.neural stem cells | mechanisms of pluripotency S elf-renewing, multipotent neural precursor cells (NPCs) are capable of terminally differentiating into neuronal and glial lineages during development and in the adult nervous system (1, 2). Disruption of the pathways controlling NPC biology has been implicated in various pathologies, including autism (3), Treacher Collins syndrome (4), and neural tube defects (5), emphasizing the importance of gaining a better understanding of the underlying molecular events and how they may be manipulated to treat and prevent such pathologies. The HMG-box transcription factor SOX2 is ubiquitously expressed in NPCs and supports their self-renewal (6). SOX2 is also required for neurogenesis in the central nervous system (7-10). Recently, we used human embryonic stem cells (hESCs) and mouse models to demonstrate a critical requirement for SOX2 for sensory neurogenesis in dorsal root ganglia (11). However, the mechanisms by which SOX2 functions in self-renewal and neuronal differentiation remain poorly understood.Small, noncoding microRNAs (miRNAs) are transcribed as long precursors (pri-miRNAs) that are sequentially processed by the RNases Drosha/Pasha to form pri-miRNAs and by Dicer to form the mature miRNAs of ∼20-25 nucleotides. The miRNAs function through imperfect base-pairing with hundreds of target mRNAs to trigger their degradation (or block their translation) by the RNA-induced silencing complex, RISC (12). In some cases, miRNA maturation is tightly controlled; for example, the RNA-binding protein LIN28 regulates the biogenesis of the let-7 miRNA family by inhibiting their maturation at both the primiRNA (13, 14) and premiRNA (15, 16) processing steps. Intriguingly, LIN28 protein was found to be associated with SO...

Newborn granule neurons generated from neural progenitor cells (NPCs) in the adult hippocampus play a key role in spatial learning and pattern separation. However, the molecular mechanisms that control activation of their neurogenic program remain poorly understood. Here, we report a novel function for the pluripotency factor sex-determining region Y (SRY)-related HMG box 2 (SOX2) in regulating the epigenetic landscape of poised genes activated at the onset of neuronal differentiation. We found that SOX2 binds to bivalently marked promoters of poised proneural genes [neurogenin 2 (Ngn2) and neurogenic differentiation 1 (NeuroD1)] and a subset of neurogenic genes [e.g., SRY-box 21 (Sox21), brain-derived neurotrophic factor (Bdnf), and growth arrest and DNA-damage-inducible, beta (Gadd45b)] where it functions to maintain the bivalent chromatin state by preventing excessive polycomb repressive complex 2 activity. Conditional ablation of SOX2 in adult hippocampal NPCs impaired the activation of proneural and neurogenic genes, resulting in increased neuroblast death and functionally aberrant newborn neurons. We propose that SOX2 sets a permissive epigenetic state in NPCs, thus enabling proper activation of the neuronal differentiation program under neurogenic cue.SOX2 | neurogenesis | epigenetics C ell fate and differentiation decisions of adult neural progenitor cells (NPCs) are controlled by intrinsic and extrinsic signals from the neurogenic niche (1-3). Recent genomewide analyses of epigenetic regulators in the brain have provided considerable insight into the mechanisms that regulate neural development, neurological disease, and aging (4, 5). The chromatin states of NPCs change dynamically during cell-fate determination and cell differentiation, and chromatin marks such as histone H3 trimethylated Lys 27 (H3K27me3), histone H3 trimethylated Lys 4 (H3K4me3), and histone H3 acetylated Lys 9 (H3K9ac) are essential for regulating the expression of key genes involved in these processes (6). Sex-determining region Y (SRY)-related HMG box 2 (SOX2) is a member of the SOXB1 family of transcription factors, which play important roles in maintaining neural stem/progenitor cell properties, including their capacity to proliferate and self-renew (7,8). In humans, SOX2 mutations are associated with anophthalmia, defective hippocampal development, and seizures (9-11). Most patients with this syndrome experience intellectual disabilities (11), suggesting that loss of SOX2 function affects areas of the brain involved in cognition (e.g., hippocampus). SOX2 deficiency also causes neurodegeneration and impaired neurogenesis in the adult mouse brain (12, 13). However, the molecular mechanisms underlying the function of SOX2 in adult neurogenesis and its role in the human SOX2 anophthalmia syndrome are largely unknown.The subgranular zone (SGZ) of the dentate gyrus (DG) in the hippocampus is a germinal zone of active neurogenesis during adulthood (14). Indeed, approximately one-third of DG neurons lost during this period are replaced ...

The recent re-emergence of Zika virus (ZIKV)1, a member of the Flaviviridae family, has become a global emergency. Currently, there are no effective methods of preventing or treating ZIKV infection, which causes severe neuroimmunopathology and is particularly harmful to the developing fetuses of infected pregnant women. However, the pathology induced by ZIKV is unique among flaviviruses, and knowledge of the biology of other family members cannot easily be extrapolated to ZIKV. Thus, structure-function studies of ZIKV proteins are urgently needed to facilitate the development of effective preventative and therapeutic agents. Like other flaviviruses, ZIKV expresses an NS2B-NS3 protease, which consists of the NS2B cofactor and the NS3 protease domain and is essential for cleavage of the ZIKV polyprotein precursor and generation of fully functional viral proteins. Here, we report the enzymatic characterization of ZIKV protease, and we identify structural scaffolds for allosteric small-molecule inhibitors of this protease. Molecular modeling of the protease-inhibitor complexes suggests that these compounds bind to the druggable cavity in the NS2B-NS3 protease interface and affect productive interactions of the protease domain with its cofactor. The most potent compound demonstrated efficient inhibition of ZIKV propagation in vitro in human fetal neural progenitor cells and in vivo in SJL mice. The inhibitory scaffolds could be further developed into valuable research reagents and, ultimately, provide a roadmap for the selection of efficient inhibitors of ZIKV infection.

One of the major challenges of the current Zika virus (ZIKV) epidemic is to prevent congenital foetal abnormalities, including microcephaly, following ZIKV infection of pregnant women. Given the urgent need for ZIKV prophylaxis and treatment, repurposing of approved drugs appears to be a viable and immediate solution. We demonstrate that the common anti-malaria drug chloroquine (CQ) extends the lifespan of ZIKV-infected interferon signalling-deficient AG129 mice. However, the severity of ZIKV infection in these mice precludes the study of foetal (vertical) viral transmission. Here, we show that interferon signalling-competent SJL mice support chronic ZIKV infection. Infected dams and sires are both able to transmit ZIKV to the offspring, making this an ideal model for in vivo validation of compounds shown to suppress ZIKV in cell culture. Administration of CQ to ZIKV-infected pregnant SJL mice during mid-late gestation significantly attenuated vertical transmission, reducing the ZIKV load in the foetal brain more than 20-fold. Given the limited side effects of CQ, its lack of contraindications in pregnant women, and its worldwide availability and low cost, we suggest that CQ could be considered for the treatment and prophylaxis of ZIKV.