A novel Cas9 fusion protein promotes targeted genome editing with reduced mutational burden in primary human cells.

Precise genome editing requires the resolution of nuclease-induced DNA double strand breaks (DSBs) via the homology-directed repair (HDR) pathway. In mammals, this is typically outcompeted by non-homologous end-joining (NHEJ) that can generate potentially genotoxic insertion/deletion mutations at DSB sites. Because of higher efficacy, clinical genome editing has been restricted to imperfect but efficient NHEJ-based approaches. Hence, strategies that promote DSB resolution via HDR are essential to facilitate clinical transition of HDR-based editing strategies and increase safety. Here we describe a novel platform that consists of a Cas9 fused to DNA repair factors to synergistically inhibit NHEJ and favor HDR for precise repairing of Cas-induced DSBs. Compared to canonical CRISPR/Cas9, the increase in error-free editing ranges from 1.5-fold to 7-fold in multiple cell lines and in primary human cells. This novel CRISPR/Cas9 platform accepts clinically relevant repair templates, such as oligodeoxynucleotides (ODNs) and adeno-associated virus (AAV)-based vectors, and has a lower propensity to induce chromosomal translocations as compared to benchmark CRISPR/Cas9. The observed reduced mutational burden, resulting from diminished indel formation at on- and off-target sites, provides a remarkable gain in safety and advocates this novel CRISPR system as an attractive tool for therapeutic applications depending on precision genome editing.

Measuring attitudes towards mental health using social media: investigating stigma and trivialisation.

BACKGROUND: There are numerous campaigns targeting mental health stigma. However, evaluating how effective these are in changing perceptions is complex. Social media may be used to assess stigma levels and highlight new trends. This study uses a social media platform, Twitter, to investigate stigmatising and trivialising attitudes across a range of mental and physical health conditions. METHODS: Tweets (i.e. messages) associated with five mental and five physical health conditions were collected in ten 72-h windows over a 50-day period using automated software. A random selection of tweets per condition was considered for the analyses. Tweets were categorised according to their topic and presence of stigmatising and trivialising attitudes. Qualitative thematic analysis was performed on all stigmatising and trivialising tweets. RESULTS: A total of 1,059,258 tweets were collected, and from this sample 1300 tweets per condition were randomly selected for analysis. Overall, mental health conditions were found to be more stigmatised (12.9%) and trivialised (14.3%) compared to physical conditions (8.1 and 6.8%, respectively). Amongst mental health conditions the most stigmatised condition was schizophrenia (41%) while the most trivialised was obsessive compulsive disorder (33%). CONCLUSIONS: Our findings show that mental health stigma is common on social media. Trivialisation is also common, suggesting that while society may be more open to discussing mental health problems, care should be taken to ensure this is done appropriately. This study further demonstrates the potential for social media to be used to measure the general public's attitudes towards mental health conditions.

Development of VariLeg, an exoskeleton with variable stiffness actuation: first results and user evaluation from the CYBATHLON 2016.

BACKGROUND: Powered exoskeletons are a promising approach to restore the ability to walk after spinal cord injury (SCI). However, current exoskeletons remain limited in their walking speed and ability to support tasks of daily living, such as stair climbing or overcoming ramps. Moreover, training progress for such advanced mobility tasks is rarely reported in literature. The work presented here aims to demonstrate the basic functionality of the VariLeg exoskeleton and its ability to enable people with motor complete SCI to perform mobility tasks of daily life. METHODS: VariLeg is a novel powered lower limb exoskeleton that enables adjustments to the compliance in the leg, with the objective of improving the robustness of walking on uneven terrain. This is achieved by an actuation system with variable mechanical stiffness in the knee joint, which was validated through test bench experiments. The feasibility and usability of the exoskeleton was tested with two paraplegic users with motor complete thoracic lesions at Th4 and Th12. The users trained three times a week, in 60 min sessions over four months with the aim of participating in the CYBATHLON 2016 competition, which served as a field test for the usability of the exoskeleton. The progress on basic walking skills and on advanced mobility tasks such as incline walking and stair climbing is reported. Within this first study, the exoskeleton was used with a constant knee stiffness. RESULTS: Test bench evaluation of the variable stiffness actuation system demonstrate that the stiffness could be rendered with an error lower than 30 Nm/rad. During training with the exoskeleton, both users acquired proficient skills in basic balancing, walking and slalom walking. In advanced mobility tasks, such as climbing ramps and stairs, only basic (needing support) to intermediate (able to perform task independently in 25% of the attempts) skill levels were achieved. After 4 months of training, one user competed at the CYBATHLON 2016 and was able to perform 3 (stand-sit-stand, slalom and tilted path) out of 6 obstacles of the track. No adverse events occurred during the training or the competition. CONCLUSION: Demonstration of the applicability to restore ambulation for people with motor complete SCI was achieved. The CYBATHLON highlighted the importance of training and gaining experience in piloting an exoskeleton, which were just as important as the technical realization of the robot.