Single-Molecule Insight Into Target Recognition by CRISPR-Cas Complexes

Ribonucleoprotein (RNP) complexes from CRISPR-Cas systems have attracted enormous interest since they can be easily and flexibly reprogrammed to target any desired locus for genome engineering and gene regulation applications. Basis for the programmability is a short RNA (crRNA) inside these complexes that recognizes the target nucleic acid by base pairing. For CRISPR-Cas systems that target double-stranded DNA this results in local DNA unwinding and formation of a so-called R-loop structure. Here we provide an overview how this target recognition mechanism can be dissected in great detail at the level of a single molecule. Specifically, we demonstrate how magnetic tweezers are applied to measure the local DNA unwinding at the target in real time. To this end we introduce the technique and the measurement principle. By studying modifications of the consensus target sequence, we show how different sequence elements contribute to the target recognition mechanism. From these data, a unified target recognition mechanism can be concluded for the RNPs Cascade and Cas9 from types I and II CRISPR-Cas systems. R-loop formation is hereby initiated on the target at an upstream element, called protospacer adjacent motif (PAM), from which the R-loop structure zips directionally toward the PAM-distal end of the target. At mismatch positions, the R-loop propagation stalls and further propagation competes with collapse of the structure. Upon full R-loop zipping conformational changes within the RNPs trigger degradation of the DNA target. This represents a shared labor mechanism in which zipping between nucleic acid strands is the actual target recognition mechanism while sensing of the R-loop arrival at the PAM-distal end just verifies the success of the full zipping.

Elevated C-reactive protein levels in schizophrenia inpatients is associated with aggressive behavior

BACKGROUND

An association between inflammation and behavioral domains of mental disorders is of growing interest. Recent studies reported an association between aggression and inflammation. In this study, we investigated the association between aggressive behavior and inflammatory markers in schizophrenia inpatients.

METHODS

Adult schizophrenia inpatients without affective symptoms (n=213) were retrospectively identified and categorized according to their C-reactive protein measurement at admission as either elevated (CRP>1 mg/dL; n=57) or normal (CRP<1 mg/dL; n=156). The following indicators of aggression were compared: PANSS excitement component (PANSS-EC), restraints and suicidal behavior during hospitalization. Univariate comparisons between elevated and normal CRP levels were performed and multivariate analysis was conducted to control for relevant covariates.

RESULTS

CRP levels significantly correlated with other laboratory markers indicating increased inflammation including leukocyte count and neutrophil to lymphocyte ratio (r=0.387, P<0.0001 and r=0.356, P<0.0001) respectively. Inpatients with elevated C-reactive protein displayed increased aggressive behavior compared to patients with normal CRP levels (<1 mg/dL). This was manifested by higher rates of restraint during hospitalization (χ(2)=5.22, P=0.031) and increased PANSS-EC score (U=5410.5, P=0.012). Elevated CRP levels were not associated with suicidal behavior. Multivariate analysis revealed that higher PANSS-EC score was associated with elevated CRP after controlling for the covariates age, sex, BMI and smoking.

CONCLUSION

This study identified a potential biological correlate (inflammation) of a specific behavioral endophenotype (aggression) in schizophrenia inpatients.

Religiosity is a protective factor against self-injurious thoughts and behaviors in Jewish adolescents: findings from a nationally representative survey

PURPOSE

Few studies have investigated the association between religiosity and self-injurious thoughts and behaviors specifically in adolescents, yielding inconsistent results. To date, no study has examined this relationship in a Jewish adolescent cohort.

METHODS

Self-injurious thoughts and behaviors, as well as depression, were assessed in a nationally representative sample of Jewish adolescents (n=620) and their mothers, using the Development and Well-Being Assessment Inventory (DAWBA) structured interview. Degree of religiosity was obtained by a self-report measure.

RESULTS

Using multivariate analysis, level of religiosity was inversely associated with self-injurious thoughts and behaviors (Wald χ(2)=3.95, P=0.047), decreasing the likelihood of occurrence by 55% (OR=0.45, 95% CI 0.2-0.99), after adjusting for depression and socio-demographic factors. This model (adjusted R(2)=0.164; likelihood ratio χ(2)=7.59; df=1; P<0.047) was able to correctly classify 95.6% of the patients as belonging either to the high or low risk groups.

CONCLUSION

This is the first study demonstrating religiosity to have a direct independent protective effect against self-injurious thoughts and behaviors in Jewish adolescents. This finding has clinical implications regarding risk assessment and suicide prevention. Further research can potentially elucidate the complex relationship between religiosity, self-injury and suicide in this population.

The use of mental health services by adolescent smokers: a nationwide Israeli study

In this study, we aimed to evaluate the utilization of mental health services by adolescent smokers, the presence of untreated mental disorders in this young population and the associated emotional and behavioral difficulties. We performed a nationwide survey study of an Israeli representative sample of 906 adolescents and their mothers. Mental disorders were assessed using the Development and Well-Being Assessment (DAWBA) Inventory. Emotional and behavioral difficulties were evaluated using the Strengths and Difficulties Questionnaire (SDQ). Mental health services use and smoking habits were evaluated by relevant questionnaires. Adolescent smokers were using significantly more mental health services than non-smokers (79% vs. 63%, respectively, P<0.001), independently of their mental health status or ethnic group. Adolescent smokers also reported more emotional and behavioral difficulties in most areas (P<0.001), which are consistent with their mothers' reports, except in the area of peer relationships. The treatment gap for the smoking adolescents was 53% compared to 69% in the non-smokers (P<0.001). This is the first study characterizing the use of mental health services and the related emotional and behavioral difficulties in a nationally-representative sample of adolescents. The findings of a wide treatment gap and the rates of the associated emotional and behavioral difficulties are highly relevant to the psychiatric assessment and national treatment plans of adolescent smokers.