CRISPR gRNA phenotypic screening in zebrafish reveals pro-regenerative genes in spinal cord injury.

Zebrafish exhibit robust regeneration following spinal cord injury, promoted by macrophages that control post-injury inflammation. However, the mechanistic basis of how macrophages regulate regeneration is poorly understood. To address this gap in understanding, we conducted a rapid in vivo phenotypic screen for macrophage-related genes that promote regeneration after spinal injury. We used acute injection of synthetic RNA Oligo CRISPR guide RNAs (sCrRNAs) that were pre-screened for high activity in vivo. Pre-screening of over 350 sCrRNAs allowed us to rapidly identify highly active sCrRNAs (up to half, abbreviated as haCRs) and to effectively target 30 potentially macrophage-related genes. Disruption of 10 of these genes impaired axonal regeneration following spinal cord injury. We selected 5 genes for further analysis and generated stable mutants using haCRs. Four of these mutants (tgfb1a, tgfb3, tnfa, sparc) retained the acute haCR phenotype, validating the approach. Mechanistically, tgfb1a haCR-injected and stable mutant zebrafish fail to resolve post-injury inflammation, indicated by prolonged presence of neutrophils and increased levels of il1b expression. Inhibition of Il-1ß rescues the impaired axon regeneration in the tgfb1a mutant. Hence, our rapid and scalable screening approach has identified functional regulators of spinal cord regeneration, but can be applied to any biological function of interest.

Lifestyle choices following head and neck cancer treatment: A qualitative study.

BACKGROUND: The benefits of a healthy lifestyle in reducing risk of cancer and chronic disease are well-documented. Many individuals who have had head and neck cancer (HNC) report complex social situations with a history of poor dietary habits, smoking and alcohol abuse. Survivorship can be a strong motivator to make positive lifestyle changes, reducing risk of cancer recurrence and ill-health. Research investigating whether HNC survivors adopt healthy lifestyle recommendations is lacking. AIM: To explore the health-related practices of post-treatment HNC patients, seeking to identify barriers and motivators to following recommended health guidelines. METHODS: Tape-recorded interviews were conducted with 20 HNC survivors, and comparisons made to Department of Health recommendations. RESULTS: 80% of participants made lifestyle changes following HNC treatment. The most prevalent changes were to diet and alcohol intake. Key motivators were reducing cancer risk and ill-health; barriers included lack of motivation, support and misinformation. Treatment side-effects presented both motivators and barriers. There was widespread recognition of the "5 a day" message, and harm caused by smoking. Other public health recommendations were less well-known; 98% were unaware of current alcohol guidelines, physical activity was overestimated, and only one participant took vitamin D. CONCLUSION: In this study HNC survivors were highly motivated to make healthy lifestyle changes. Further work is required to increase awareness of Government guidelines, as health messages are not always reaching the public or are misinterpreted.

Truly-Biocompatible Gold Catalysis Enables Vivo-Orthogonal Intra-CNS Release of Anxiolytics.

Being recognized as the best-tolerated of all metals, the catalytic potential of gold (Au) has thus far been hindered by the ubiquitous presence of thiols in organisms. Herein we report the development of a truly-catalytic Au-polymer composite by assembling ultrasmall Au-nanoparticles at the protein-repelling outer layer of a co-polymer scaffold via electrostatic loading. Illustrating the in vivo-compatibility of the novel catalysts, we show their capacity to uncage the anxiolytic agent fluoxetine at the central nervous system (CNS) of developing zebrafish, influencing their swim pattern. This bioorthogonal strategy has enabled -for the first time- modification of cognitive activity by releasing a neuroactive agent directly in the brain of an animal.

Behavioral observation of Xenopus tadpole swimming for neuroscience labs.

Neuroscience labs benefit from reliable, easily-monitored neural responses mediated by well-studied neural pathways. Xenopus laevis tadpoles have been used as a simple vertebrate model preparation in motor control studies. Most of the neuronal pathways underlying different aspects of tadpole swimming behavior have been revealed. These include the skin mechanosensory touch and pineal eye light-sensing pathways whose activation can initiate swimming, and the cement gland pressure-sensing pathway responsible for stopping swimming. A simple transection in the hindbrain can cut off the pineal eye and cement gland pathways from the swimming circuit in the spinal cord, resulting in losses of corresponding functions. Additionally, some pharmacological experiments targeting neurotransmission can be designed to affect swimming and, fluorescence-conjugated α-bungarotoxin can be used to label nicotinic receptors at neuromuscular junctions. These experiments can be readily adapted for undergraduate neuroscience teaching labs. Possible expansions of some experiments for more sophisticated pharmacological or neurophysiological labs are also discussed.

Truly-Biocompatible Gold Catalysis Enables Vivo-Orthogonal Intra-CNS Release of Anxiolytics.

Being recognized as the best-tolerated of all metals, the catalytic potential of gold (Au) has thus far been hindered by the ubiquitous presence of thiols in organisms. Herein we report the development of a truly-catalytic Au-polymer composite by assembling ultrasmall Au-nanoparticles at the protein-repelling outer layer of a co-polymer scaffold via electrostatic loading. Illustrating the in vivo-compatibility of the novel catalysts, we show their capacity to uncage the anxiolytic agent fluoxetine at the central nervous system (CNS) of developing zebrafish, influencing their swim pattern. This bioorthogonal strategy has enabled -for the first time- modification of cognitive activity by releasing a neuroactive agent directly in the brain of an animal.

Muscarinic modulation of the Xenopus laevis tadpole spinal mechanosensory pathway.

Muscarinic acetylcholine receptors (mAChRs) mediate effects of acetylcholine (ACh) in many systems, including those involved in spinal functions like locomotion. In Xenopus laevis tadpoles at two days old, a model vertebrate for motor control research, we investigated the role of mAChRs in the skin mechanosensory pathway. We found that mAChR activation by carbachol did not affect the sensory Rohon-Beard neuron properties. However, carbachol could hyperpolarise sensory interneurons and decrease their voltage responses to outward currents. Carbachol could increase the threshold for the mechanosensory pathway to start swimming, preventing the initiation of swimming at higher concentrations altogether. Recording from the sensory interneurons in carbachol showed that their spiking after skin stimulation was depressed. However, the general muscarinic antagonist atropine did not have a clear effect on the swimming threshold or the modulation of sensory interneuron membrane conductance. Our results suggest the skin mechanosensory pathway may be subject to muscarinic modulation in this simple vertebrate system.

Stereology and ultrastructure of chronic phase axonal and cell soma pathology in stretch-injured central nerve fibers.

Magnetic resonance imaging (MRI) suggests that with survival after human traumatic brain injury (TBI), there is ongoing loss of white and grey matter from the injured brain during the chronic phase. However; direct quantitative experimental evidence in support of this observation is lacking. Using the guinea pig stretch-injury optic nerve model, quantitative evidence by stereology of damage to the optic nerve and retina was sought. Stretch injury was applied to the right optic nerve of 15 adult male guinea pigs. Three animals each at 1, 2, 3, 8, or 12 weeks' survival were killed and prepared for transmission electron microscopy (TEM). The estimated number of intact and injured axons within bins of transverse diameters 0-0.5, 0.51-1.0, 1.01-1.5, 1.51-2.0, 2.01-2.5, and 2.51-3.0 µm in the middle segment of each injured optic nerve and from 5 control animals were compared across all survival time points. The estimated numbers of intact and pyknotic retinal ganglion cells from the same animals were also compared. Loss of myelinated fibers continued throughout the experimental period. The most rapid loss was of the largest fibers; loss of intermediate-sized fibers continued, but the numbers of the smallest fibers increased from 3 weeks onward. There was hypertrophy and proliferation of glial cells within the surrounding neuropil. A relatively low-grade loss of retinal ganglion cells occurred throughout the experiment, with about 60% remaining at 12 weeks' survival. We provide quantitative evidence that after traumatic axonal injury (TAI) there is a continuing loss of nerve fibers and their cell bodies from a CNS tract over a 3-month post-traumatic interval.