Regulating the expression of gene drives is key to increasing their invasive potential and the mitigation of resistance

Homing-based gene drives use a germline source of nuclease to copy themselves at specific target sites in a genome and bias their inheritance. Such gene drives can be designed to spread and deliberately suppress populations of malaria mosquitoes by impairing female fertility. However, strong unintended fitness costs of the drive and a propensity to generate resistant mutations can limit a gene drive’s potential to spread. Alternative germline regulatory sequences in the drive element confer improved fecundity of carrier individuals and reduced propensity for target site resistance. This is explained by reduced rates of end-joining repair of DNA breaks from parentally deposited nuclease in the embryo, which can produce heritable mutations that reduce gene drive penetrance. We tracked the generation and selection of resistant mutations over the course of a gene drive invasion of a population. Improved gene drives show faster invasion dynamics, increased suppressive effect and later onset of target site resistance. Our results show that regulation of nuclease expression is as important as the choice of target site when developing a robust homing-based gene drive for population suppression

The Molecular Tumor Board Portal supports clinical decisions and automated reporting for precision oncology.

There is a growing need for systems that efficiently support the work of medical teams at the precision-oncology point of care. Here, we present the implementation of the Molecular Tumor Board Portal (MTBP), an academic clinical decision support system developed under the umbrella of Cancer Core Europe that creates a unified legal, scientific and technological platform to share and harness next-generation sequencing data. Automating the interpretation and reporting of sequencing results decrease the need for time-consuming manual procedures that are prone to errors. The adoption of an expert-agreed process to systematically link tumor molecular profiles with clinical actions promotes consistent decision-making and structured data capture across the connected centers. The use of information-rich patient reports with interactive content facilitates collaborative discussion of complex cases during virtual molecular tumor board meetings. Overall, streamlined digital systems like the MTBP are crucial to better address the challenges brought by precision oncology and accelerate the use of emerging biomarkers

Staging of Schizophrenia with the Use of PANSS: An International Multi-Center Study

Introduction: A specific clinically relevant staging model for schizophrenia has not yet been developed. The aim of the current study was to evaluate the factor structure of the PANSS and develop such a staging method.Methods: Twenty-nine centers from 25 countries contributed 2358 patients aged 37.21 ± 11.87 years with schizophrenia. Analysis of covariance, Exploratory Factor Analysis, Discriminant Function Analysis, and inspection of resultant plots were performed.Results: Exploratory Factor Analysis returned 5 factors explaining 59% of the variance (positive, negative, excitement/hostility, depression/anxiety, and neurocognition). The staging model included 4 main stages with substages that were predominantly characterized by a single domain of symptoms (stage 1: positive; stages 2a and 2b: excitement/hostility; stage 3a and 3b: depression/anxiety; stage 4a and 4b: neurocognition). There were no differences between sexes. The Discriminant Function Analysis developed an algorithm that correctly classified >85% of patients.Discussion: This study elaborates a 5-factor solution and a clinical staging method for patients with schizophrenia. It is the largest study to address these issues among patients who are more likely to remain affiliated with mental health services for prolonged periods of time.<br /

The creation and selection of mutations resistant to a gene drive over multiple generations in the malaria mosquito

Gene drives have enormous potential for the control of insect populations of medical and agricultural relevance. By preferentially biasing their own inheritance, gene drives can rapidly introduce genetic traits even if these confer a negative fitness effect on the population. We have recently developed gene drives based on CRISPR nuclease constructs that are designed to disrupt key genes essential for female fertility in the malaria mosquito. The construct copies itself and the associated genetic disruption from one homologous chromosome to another during gamete formation, a process called homing that ensures the majority of offspring inherit the drive. Such drives have the potential to cause long-lasting, sustainable population suppression, though they are also expected to impose a large selection pressure for resistance in the mosquito. One of these population suppression gene drives showed rapid invasion of a caged population over 4 generations, establishing proof of principle for this technology. In order to assess the potential for the emergence of resistance to the gene drive in this population we allowed it to run for 25 generations and monitored the frequency of the gene drive over time. Following the initial increase of the gene drive we observed a gradual decrease in its frequency that was accompanied by the spread of small, nuclease-induced mutations at the target gene that are resistant to further cleavage and restore its functionality. Such mutations showed rates of increase consistent with positive selection in the face of the gene drive. Our findings represent the first documented example of selection for resistance to a synthetic gene drive and lead to important design recommendations and considerations in order to mitigate for resistance in future gene drive applications

Dynamics of a population suppression gene drive construct over 25 generations.

<p><b>(A)</b> Design of the CRISPR-based gene drive construct and the relevant position of its target site within AGAP007280; <b>(B)</b> The proportion of individuals containing at least one copy of the gene drive in two replicate cages, monitored each generation for 25 generations. Black lines represent the observed frequencies in each of the two cage trials (CT1 and CT2), red line represents the predicted frequency according to the previous deterministic model that did not take into account target site resistance [<a href="http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.1007039#pgen.1007039.ref011" target="_blank">11</a>]. Samples were taken for pooled PCR and sequencing analysis of the gene drive target site at G₂ and at G₁₂, whereby frequency of target site indels (shown figuratively as red bars) were revealed by their relative representation among the sequenced reads.</p

Target site mutations under positive selection are resistant to gene drive activity and restore function to the target female fertility gene.

<p><b>(A)</b> Individual females containing at least one copy of the gene drive (RFP+) were selected from the G₂₀ generation and the nature of the target allele was determined by PCR and sequencing. Each class of allele is shown with gene drive target sequence highlighted in red and PAM sequence underlined. <b>(B)</b> The fecundity of these females and transmission rates of the gene drive were measured and grouped according to allele class at the target site. <b>(C)</b> Each <i>CRISPR</i>^<i>h</i><i>/r</i> female was used to form a separate lineage and transmission of the gene drive was assessed in sons receiving a maternal copy of the gene drive. A smaller fraction of grandsons receiving a paternal copy of the gene drive were similarly assessed for gene drive transmission. Individual lineages assessed in all three generations are marked in red. † Of 58 mated females one (with deletion 207+AAAGTC) failed to produce eggs while another (202–TGAGGA) produced eggs that failed to hatch.</p

Comparison of observed data with model predicting frequencies of gene drive and resistance alleles.

<p><b>(A)</b> Expected genotype frequencies according to the model described in the text and considering the four following target site alleles: wild type (w), <i>CRISPR^h</i> gene drive (h), resistant and in-frame (r1), resistant and out of frame (r2). We used our best experimental estimates of the considered parameters: homing rate (<i>e</i>) as 0.984, the dominance of the fertility effect due to leaky somatic expression in females heterozygous (<i>w/h</i>) for the gene drive as 0.907, meiotic end-joining rate (γ_m) as 0.01, embryonic end-joining rate (γ_e) as 0.796. <b>(B)</b> Our observed gene drive frequencies were compared against model predictions using our best experimental estimates (solid black line) and using the best-fit value (0.70 cf 0.907) for dominance of the heterozygous fertility effect in females (dashed black line).</p

Gender, age at onset, and duration of being ill as predictors for the long-term course and outcome of schizophrenia : an international multicenter study

Background The aim of the current study was to explore the effect of gender, age at onset, and duration on the long-term course of schizophrenia. Methods Twenty-nine centers from 25 countries representing all continents participated in the study that included 2358 patients aged 37.21 +/- 11.87 years with a DSM-IV or DSM-5 diagnosis of schizophrenia; the Positive and Negative Syndrome Scale as well as relevant clinicodemographic data were gathered. Analysis of variance and analysis of covariance were used, and the methodology corrected for the presence of potentially confounding effects. Results There was a 3-year later age at onset for females (P &lt; .001) and lower rates of negative symptoms (P &lt; .01) and higher depression/anxiety measures (P &lt; .05) at some stages. The age at onset manifested a distribution with a single peak for both genders with a tendency of patients with younger onset having slower advancement through illness stages (P = .001). No significant effects were found concerning duration of illness. Discussion Our results confirmed a later onset and a possibly more benign course and outcome in females. Age at onset manifested a single peak in both genders, and surprisingly, earlier onset was related to a slower progression of the illness. No effect of duration has been detected. These results are partially in accord with the literature, but they also differ as a consequence of the different starting point of our methodology (a novel staging model), which in our opinion precluded the impact of confounding effects. Future research should focus on the therapeutic policy and implications of these results in more representative samples

Modeling psychological function in patients with schizophrenia with the PANSS: an international multi-center study.

BACKGROUND.: The aim of the current study was to explore the changing interrelationships among clinical variables through the stages of schizophrenia in order to assemble a comprehensive and meaningful disease model. METHODS.: Twenty-nine centers from 25 countries participated and included 2358 patients aged 37.21 ± 11.87 years with schizophrenia. Multiple linear regression analysis and visual inspection of plots were performed. RESULTS.: The results suggest that with progression stages, there are changing correlations among Positive and Negative Syndrome Scale factors at each stage and each factor correlates with all the others in that particular stage, in which this factor is dominant. This internal structure further supports the validity of an already proposed four stages model, with positive symptoms dominating the first stage, excitement/hostility the second, depression the third, and neurocognitive decline the last stage. CONCLUSIONS.: The current study investigated the mental organization and functioning in patients with schizophrenia in relation to different stages of illness progression. It revealed two distinct "cores" of schizophrenia, the "Positive" and the "Negative," while neurocognitive decline escalates during the later stages. Future research should focus on the therapeutic implications of such a model. Stopping the progress of the illness could demand to stop the succession of stages. This could be achieved not only by both halting the triggering effect of positive and negative symptoms, but also by stopping the sensitization effect on the neural pathways responsible for the development of hostility, excitement, anxiety, and depression as well as the deleterious effect on neural networks responsible for neurocognition.status: Published onlin