Core/shell nanoparticles composed of a silica core over which a propargyl methacrylate (PMA) shell was polymerized around were synthesized. To employ the shell coating, the surface of the silica nanoparticles (SiNPs) was modified with an alkene-terminated organometallic silane linker that allowed for the covalent attachment of a poly(propargyl methacrylate) (pPMA) shell. The alkyne groups resulting from the pPMA shell were utilized in copper(I)-catalyzed azide/alkyne cycloaddition (CuAAC) reactions to attach azide-modified Förster resonance energy transfer (FRET) pairs of naphthalimide (azNap), rhodamine B (azRhod), and silicon phthalocyanine (azSiPc) derivatives to the shell surface. The luminescence of the system was manipulated by the covalent attachment of one, two, or three of the fluorophores resulting in no energy transfer, one energy transfer, or two energy transfers, respectively. When all three fluorophores were attached to the core/shell particles, an excitation of azNap with a wavelength of 400 nm resulted in the sequential energy transfer between two FRET pairs and the sole emission of azSiPc at 670 nm. These particles may have applications as bioimaging probes as their luminescence is easily detected using fluorescence microscopy.
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Abstract Background Fetal alcohol syndrome (FAS) due to gestational alcohol exposure represents one of the most common causes of nonheritable lifelong disability worldwide. In vitro and in vivo models have successfully recapitulated multiple facets of the disorder, including morphological and behavioral deficits, but far less is understood regarding the molecular and genetic mechanisms underlying FAS.
Methods In this study, we utilized an in vitro human pluripotent stem cell‐based (hPSC) model of corticogenesis to probe the effects of early, chronic intermittent alcohol exposure on the transcriptome of first trimester‐equivalent cortical neurons.
Results We used RNA sequencing of developing hPSC‐derived neurons treated for 50 days with 50 mM ethanol and identified a relatively small number of biological pathways significantly altered by alcohol exposure. These included cell‐type specification, axon guidance, synaptic function, and regional patterning, with a notable upregulation of WNT signaling‐associated transcripts observed in alcohol‐exposed cultures relative to alcohol‐naïve controls. Importantly, this effect paralleled a shift in gene expression of transcripts associated with regional patterning, such that caudal forebrain‐related transcripts were upregulated at the expense of more anterior ones. Results from H9 embryonic stem cells were largely replicated in an induced pluripotent stem cell line (IMR90‐4), indicating that these patterning alterations are not cell line‐specific.
Conclusions We found that a major effect of chronic intermittent alcohol on the developing cerebral cortex is an overall imbalance in regionalization, with enrichment of gene expression related to the production of posterodorsal progenitors and a diminution of anteroventral progenitors. This finding parallels behavioral and morphological phenotypes observed in animal models of high‐dose prenatal alcohol exposure, as well as patients with FAS.
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Abstract Adult neurogenesis is necessary for proper cognition and behavior, however, the mechanisms that underlie the integration and maturation of newborn neurons into the pre‐existing hippocampal circuit are not entirely known. In this study, we sought to determine the role of action potential (AP)‐dependent synaptic transmission by adult‐generated dentate granule cells (DGCs) in their survival and function within the existing circuitry. We used a triple transgenic mouse (NestinCreERT2:Snap25fl/fl: tdTomato) to inducibly inactivate AP‐dependent synaptic transmission within adult hippocampal progenitors and their progeny. Behavioral testing in a hippocampal‐dependent A/B contextual fear‐discrimination task revealed impaired discrimination learning in mice harboring SNAP‐25‐deficient adult‐generated dentate granule cells (DGCs). Despite poor performance on this neurogenesis‐dependent task, the production and survival of newborn DGCs was quantitatively unaltered in tamoxifen‐treated NestinCreERT2:Snap25fl/fl: tdTomato SNAP compared to tamoxifen‐treated NestinCreERT2:Snap25wt/wt: tdTomato control mice. Although SNAP‐25‐deficient adult DGCs displayed a small but statistically significant enhancement in proximal dendritic branching, their overall dendritic length and distal branching complexity was unchanged. SNAP‐25‐deficient newborn DGCs also displayed robust efferent mossy fiber output to CA3, with normal linear density of large mossy fiber terminals (LMTs). These studies suggest that AP‐dependent neurotransmitter release by newborn DGCs is not essential for their survival or rudimentary structural maturation within the adult hippocampus.
