LNA blockers for improved amplification selectivity.

LNA-containing oligonucleotides bind DNA more tightly than standard DNA, so they can interact with targeted sequences and affect multiple processes. When a desired DNA is present at low concentrations relative to nearly identical undesired DNAs, LNAs can block amplification of unwanted DNAs. Using a short rAAV and synthetic DNA sequence as a model, we studied the length, number, and positioning of LNA bases to improve blocker effectiveness. Oligonucleotides 18-24 bases long with LNAs at every other position were most effective. Highly degenerate targets were used to characterize the impact of mismatches on blocking. Mismatches at LNA ends had little impact on blocking activity. Single and double mismatches were tolerated with longer blockers, especially if the mismatches were near LNA ends. Shorter LNAs were more selective, with > 1 mismatch preventing effective blocking. Neither the strand to which a blocker bound nor the distance between the blocker and priming sites greatly impacted blocking efficiency. We used these findings to design blockers of wild-type DNA versus the single-base A1AT PiZ allele. Blockers are most specific when the mismatch is located away from the LNA 5' end. Pairs of partially overlapping blockers on opposite strands with a centrally-located mismatch have maximal activity and specificity.

The Mediating Effect of Caregiving Relationship Quality on the Association Between Caregiving Stressors and Mental Health Problems Among Older Spousal Caregivers.

Providing care to a spouse can be especially challenging for older adults given their compounding stressors resulting from aging and caregiving. This cross-sectional study examines the relationships between caregiving stressors and caregiver mental health problems and the potential mediator (i.e., caregiving relationship quality) of these associations. A total of 431 Americans (≥65 years) were selected from the National Study of Caregiving. Path analysis shows that care assistance was positively associated with caregiver mental health problems, and this association was mediated by negative relationship quality (Indirect effect = .14, p = .016). Moreover, role overload was positively associated with caregiver mental health problems, which was mediated by negative relationship quality (indirect effect = .13, p = .002). Findings suggest that caregiving stressors can adversely affect mental health by exacerbating negative relationship quality. Interventions that limit negative exchanges and increase compassionate communications between older spousal caregivers and their care-receiving partners are needed.

"Intelligent Justice": human-centered considerations in China's legal AI transformation.

In recent years, the Chinese government and its judiciary have made a policy decision to leverage artificial intelligence in broader judicial reform efforts. The push to use AI to such a large extent in the judiciary is unique to China, influenced by chronic challenges facing the courts, including an exponential increase in casework and a shortage of qualified professionals in the judiciary. This has resulted in a number of pilot programs across the country that have produced various AI systems embedded in different areas of the judicial system. Some of these systems aim to make rote processes, such as transcription and document review, more efficient, while other more ambitious projects attempt to directly assist in the decision-making process. This piece briefly summarizes the current landscape of China's technology-driven judicial reform and highlights a number of key considerations that we believe are pivotal to whether China's investment in AI will succeed in improving the efficiency and legitimacy of the courts.

Molecular characterization of precise in vivo targeted gene integration in human cells using AAVHSC15.

Targeted gene integration via precise homologous recombination (HR)-based gene editing has the potential to correct genetic diseases. AAV (adeno-associated virus) can mediate nuclease-free gene integration at a disease-causing locus. Therapeutic application of AAV gene integration requires quantitative molecular characterization of the edited sequence that overcome technical obstacles such as excess episomal vector genomes and lengthy homology arms. Here we describe a novel molecular methodology that utilizes quantitative next-generation sequencing to characterize AAV-mediated targeted insertion and detects the presence of unintended mutations. The methods described here quantify targeted insertion and query the entirety of the target locus for the presence of insertions, deletions, single nucleotide variants (SNVs) and integration of viral components such as inverted terminal repeats (ITR). Using a humanized liver murine model, we demonstrate that hematopoietic stem-cell derived AAVHSC15 mediates in vivo targeted gene integration into human chromosome 12 at the PAH (phenylalanine hydroxylase) locus at 6% frequency, with no sign of co-incident random mutations at or above a lower limit of detection of 0.5% and no ITR sequences at the integration sites. Furthermore, analysis of heterozygous variants across the targeted locus using the methods described shows a pattern of strand cross-over, supportive of an HR mechanism of gene integration with similar efficiencies across two different haplotypes. Rapid advances in the application of AAV-mediated nuclease-free target integration, or gene editing, as a new therapeutic modality requires precise understanding of the efficiency and the nature of the changes being introduced to the target genome at the molecular level. This work provides a framework to be applied to homologous recombination gene editing platforms for assessment of introduced and natural sequence variation across a target site.

Opposing Cholinergic and Serotonergic Modulation of Layer 6 in Prefrontal Cortex.

Prefrontal cortex is a hub for attention processing and receives abundant innervation from cholinergic and serotonergic afferents. A growing body of evidence suggests that acetylcholine (ACh) and serotonin (5-HT) have opposing influences on tasks requiring attention, but the underlying neurophysiology of their opposition is unclear. One candidate target population is medial prefrontal layer 6 pyramidal neurons, which provide feedback modulation of the thalamus, as well as feed-forward excitation of cortical interneurons. Here, we assess the response of these neurons to ACh and 5-HT using whole cell recordings in acute brain slices from mouse cortex. With application of exogenous agonists, we show that individual layer 6 pyramidal neurons are bidirectionally-modulated, with ACh and 5-HT exerting opposite effects on excitability across a number of concentrations. Next, we tested the responses of layer 6 pyramidal neurons to optogenetic release of endogenous ACh or 5-HT. These experiments were performed in brain slices from transgenic mice expressing channelrhodopsin in either ChAT-expressing cholinergic neurons or Pet1-expressing serotonergic neurons. Light-evoked endogenous neuromodulation recapitulated the effects of exogenous neurotransmitters, showing opposing modulation of layer 6 pyramidal neurons by ACh and 5-HT. Lastly, the addition of 5-HT to either endogenous or exogenous ACh significantly suppressed the excitation of pyramidal neurons in prefrontal layer 6. Taken together, this work suggests that the major corticothalamic layer of prefrontal cortex is a substrate for opposing modulatory influences on neuronal activity that could have implications for regulation of attention.

Serotonergic Suppression of Mouse Prefrontal Circuits Implicated in Task Attention.

Serotonin (5-HT) regulates attention by neurobiological mechanisms that are not well understood. Layer 6 (L6) pyramidal neurons of prefrontal cortex play an important role in attention and express 5-HT receptors, but the serotonergic modulation of this layer and its excitatory output is not known. Here, we performed whole-cell recordings and pharmacological manipulations in acute brain slices from wild-type and transgenic mice expressing either eGFP or eGFP-channelrhodopsin in prefrontal L6 pyramidal neurons. Excitatory circuits between L6 pyramidal neurons and L5 GABAergic interneurons, including a population of interneurons essential for task attention, were investigated using optogenetic techniques. Our experiments show that prefrontal L6 pyramidal neurons are subject to strong serotonergic inhibition and demonstrate direct 5-HT-sensitive connections between prefrontal L6 pyramidal neurons and two classes of L5 interneurons. This work helps to build a neurobiological framework to appreciate serotonergic disruption of task attention and yields insight into the disruptions of attention observed in psychiatric disorders with altered 5-HT receptors and signaling.

Dendritic spine density of prefrontal layer 6 pyramidal neurons in relation to apical dendrite sculpting by nicotinic acetylcholine receptors.

Prefrontal layer 6 (L6) pyramidal neurons play an important role in the adult control of attention, facilitated by their strong activation by nicotinic acetylcholine receptors. These neurons in mouse association cortex are distinctive morphologically when compared to L6 neurons in primary cortical regions. Roughly equal proportions of the prefrontal L6 neurons have apical dendrites that are "long" (reaching to the pial surface) vs. "short" (terminating in the deep layers, as in primary cortical regions). This distinct prefrontal morphological pattern is established in the post-juvenile period and appears dependent on nicotinic receptors. Here, we examine dendritic spine densities in these two subgroups of prefrontal L6 pyramidal neurons under control conditions as well as after perturbation of nicotinic acetylcholine receptors. In control mice, the long neurons have significantly greater apical and basal dendritic spine density compared to the short neurons. Furthermore, manipulations of nicotinic receptors (chrna5 deletion or chronic developmental nicotine exposure) have distinct effects on these two subgroups of L6 neurons: apical spine density is significantly reduced in long neurons, and basal spine density is significantly increased in short neurons. These changes appear dependent on the α5 nicotinic subunit encoded by chrna5. Overall, the two subgroups of prefrontal L6 neurons appear positioned to integrate information either across cortex (long neurons) or within the deep layers (short neurons), and nicotinic perturbations differently alter spine density within each subgroup.

Discrimination of closely related species in tintinnid ciliates: new insights on crypticity and polymorphism in the genus Helicostomella.

This study focuses on the utility of molecular markers for the discrimination of closely related species in tintinnid ciliates. We analyzed the ecologically important genus Helicostomella by sequencing part of the large-subunit rDNA (LSU rDNA) and the 5.8S rDNA combined with the internally transcribed spacer regions 1 and 2 (5.8S rDNA-ITS) from forty-five individuals collected in NW and SW Atlantic waters and after culturing. Although all described Helicostomella species represent a continuum of morphologies, forms with shorter or longer loricae would correspond to different species according to previous molecular data. Here we observed that long forms show both crypticity (i.e. two almost identical long forms with different DNA sequences) and polymorphism (i.e. some long forms develop significantly shorter loricae after culturing). Reviewing all available tintinnid sequences, we found that 1) three Helicostomella clusters are consistent with different species from a molecular perspective, although these clusters are neither clearly differentiated by their loricae nor unambiguously linked to described species, 2) Helicostomella is closely related (probably to the family or genus level) to four "Tintinnopsis-like" morphospecies, and 3) if considered separately, neither LSU rDNA nor 5.8S rDNA-ITS completely discriminate closely related species, thus supporting the use of multi-gene barcodes for tintinnids.

Cholinergic excitation in mouse primary vs. associative cortex: region-specific magnitude and receptor balance.

Cholinergic stimulation of the cerebral cortex is essential for tasks requiring attention; however, there is still some debate over which cortical regions are required for such tasks. There is extensive cholinergic innervation of both primary and associative cortices, and transient release of acetylcholine (ACh) is detected in deep layers of the relevant primary and/or associative cortex, depending on the nature of the attention task. Here, we investigated the electrophysiological effects of ACh in layer VI, the deepest layer, of the primary somatosensory cortex, the primary motor cortex, and the associative medial prefrontal cortex. Layer VI pyramidal neurons are a major source of top-down modulation of attention, and we found that the strength and homogeneity of their direct cholinergic excitation was region-specific. On average, neurons in the primary cortical regions showed weaker responses to ACh, mediated by a balance of contributions from both nicotinic and muscarinic ACh receptors. Conversely, neurons in the associative medial prefrontal cortex showed significantly stronger excitation by ACh, mediated predominantly by nicotinic receptors. The greatest diversity of responses to ACh was found in the primary somatosensory cortex, with only a subset of neurons showing nicotinic excitation. In a mouse model with attention deficits only under demanding conditions, cholinergic excitation was preserved in primary cortical regions but not in the associative medial prefrontal cortex. These findings demonstrate that the effect of ACh is not uniform throughout the cortex, and suggest that its ability to enhance attention performance may involve different cellular mechanisms across cortical regions.

Nicotinic acetylcholine receptors in attention circuitry: the role of layer VI neurons of prefrontal cortex.

Cholinergic modulation of prefrontal cortex is essential for attention. In essence, it focuses the mind on relevant, transient stimuli in support of goal-directed behavior. The excitation of prefrontal layer VI neurons through nicotinic acetylcholine receptors optimizes local and top-down control of attention. Layer VI of prefrontal cortex is the origin of a dense feedback projection to the thalamus and is one of only a handful of brain regions that express the α5 nicotinic receptor subunit, encoded by the gene chrna5. This accessory nicotinic receptor subunit alters the properties of high-affinity nicotinic receptors in layer VI pyramidal neurons in both development and adulthood. Studies investigating the consequences of genetic deletion of α5, as well as other disruptions to nicotinic receptors, find attention deficits together with altered cholinergic excitation of layer VI neurons and aberrant neuronal morphology. Nicotinic receptors in prefrontal layer VI neurons play an essential role in focusing attention under challenging circumstances. In this regard, they do not act in isolation, but rather in concert with cholinergic receptors in other parts of prefrontal circuitry. This review urges an intensification of focus on the cellular mechanisms and plasticity of prefrontal attention circuitry. Disruptions in attention are one of the greatest contributing factors to disease burden in psychiatric and neurological disorders, and enhancing attention may require different approaches in the normal and disordered prefrontal cortex.

Chrna5 genotype determines the long-lasting effects of developmental in vivo nicotine exposure on prefrontal attention circuitry.

Maternal smoking during pregnancy repeatedly exposes the developing fetus to nicotine and is linked with attention deficits in offspring. Corticothalamic neurons within layer VI of the medial prefrontal cortex are potential targets in the disruption of attention circuitry by nicotine, a process termed teratogenesis. These prefrontal layer VI neurons would be likely targets because they are developmentally excited and morphologically sculpted by a population of nicotinic acetylcholine receptors (nAChRs) that are sensitive to activation and/or desensitization by nicotine. The maturational effects of these α4ß2* nAChRs and their susceptibility to desensitization are both profoundly altered by the incorporation of an α5 subunit, encoded by the chrna5 gene. Here, we investigate nicotine teratogenesis in layer VI neurons of wildtype and α5(-/-) mice. In vivo chronic nicotine exposure during development significantly modified apical dendrite morphology and nAChR currents, compared with vehicle control. The direction of the changes was dependent on chrna5 genotype. Surprisingly, neurons from wildtype mice treated with in vivo nicotine resembled those from α5(-/-) mice treated with vehicle, maintaining into adulthood a morphological phenotype characteristic of immature mice together with reduced nAChR currents. In α5(-/-) mice, however, developmental in vivo nicotine tended to normalize both adult morphology and nAChR currents. These findings suggest that chrna5 genotype can determine the effect of developmental in vivo nicotine on the prefrontal cortex. In wildtype mice, the lasting alterations to the morphology and nAChR activation of prefrontal layer VI neurons are teratogenic changes consistent with the attention deficits observed following developmental nicotine exposure.

Plasticity of prefrontal attention circuitry: upregulated muscarinic excitability in response to decreased nicotinic signaling following deletion of α5 or ß2 subunits.

Attention depends on cholinergic stimulation of nicotinic and muscarinic acetylcholine receptors in the medial prefrontal cortex. Pyramidal neurons in layer VI of this region express cholinergic receptors of both families and play an important role in attention through their feedback projections to the thalamus. Here, we investigate how nicotinic and muscarinic cholinergic receptors affect the excitability of these neurons using whole-cell recordings in acute brain slices of prefrontal cortex. Since attention deficits have been documented in both rodents and humans having genetic abnormalities in nicotinic receptors, we focus in particular on how the cholinergic excitation of layer VI neurons is altered by genetic deletion of either of two key nicotinic receptor subunits, the accessory α5 subunit or the ligand-binding ß2 subunit. We find that the cholinergic excitation of layer VI neurons is dominated by nicotinic receptors in wild-type mice and that the reduction or loss of this nicotinic stimulation is accompanied by a surprising degree of plasticity in excitatory muscarinic receptors. These findings suggest that disrupting nicotinic receptors fundamentally alters the mechanisms and timing of excitation in prefrontal attentional circuitry.