Microglial over-pruning of synapses during development in autism-associated SCN2A-deficient mice and human cerebral organoids.

Autism spectrum disorder (ASD) is a major neurodevelopmental disorder affecting 1 in 36 children in the United States. While neurons have been the focus of understanding ASD, an altered neuro-immune response in the brain may be closely associated with ASD, and a neuro-immune interaction could play a role in the disease progression. As the resident immune cells of the brain, microglia regulate brain development and homeostasis via core functions including phagocytosis of synapses. While ASD has been traditionally considered a polygenic disorder, recent large-scale human genetic studies have identified SCN2A deficiency as a leading monogenic cause of ASD and intellectual disability. We generated a Scn2a-deficient mouse model, which displays major behavioral and neuronal phenotypes. However, the role of microglia in this disease model is unknown. Here, we reported that Scn2a-deficient mice have impaired learning and memory, accompanied by reduced synaptic transmission and lower spine density in neurons of the hippocampus. Microglia in Scn2a-deficient mice are partially activated, exerting excessive phagocytic pruning of post-synapses related to the complement C3 cascades during selective developmental stages. The ablation of microglia using PLX3397 partially restores synaptic transmission and spine density. To extend our findings from rodents to human cells, we established a microglia-incorporated human cerebral organoid model carrying an SCN2A protein-truncating mutation identified in children with ASD. We found that human microglia display increased elimination of post-synapse in cerebral organoids carrying the SCN2A mutation. Our study establishes a key role of microglia in multi-species autism-associated models of SCN2A deficiency from mouse to human cells.

Microglial over-pruning of synapses during development in autism-associated SCN2A-deficient mice and human cerebral organoids.

Autism spectrum disorder (ASD) is a major neurodevelopmental disorder affecting 1 in 36 children in the United States. While neurons have been the focus to understand ASD, an altered neuro-immune response in the brain may be closely associated with ASD, and a neuro-immune interaction could play a role in the disease progression. As the resident immune cells of the brain, microglia regulate brain development and homeostasis via core functions including phagocytosis of synapses. While ASD has been traditionally considered a polygenic disorder, recent large-scale human genetic studies have identified SCN2A deficiency as a leading monogenic cause of ASD and intellectual disability. We generated a Scn2a-deficient mouse model, which displays major behavioral and neuronal phenotypes. However, the role of microglia in this disease model is unknown. Here, we reported that Scn2a-deficient mice have impaired learning and memory, accompanied by reduced synaptic transmission and lower spine density in neurons of the hippocampus. Microglia in Scn2a-deficient mice are partially activated, exerting excessive phagocytic pruning of post-synapses related to the complement C3 cascades during selective developmental stages. The ablation of microglia using PLX3397 partially restores synaptic transmission and spine density. To extend our findings from rodents to human cells, we established a microglial-incorporated human cerebral organoid model carrying an SCN2A protein-truncating mutation identified in children with ASD. We found that human microglia display increased elimination of post-synapse in cerebral organoids carrying the SCN2A mutation. Our study establishes a key role of microglia in multi-species autism-associated models of SCN2A deficiency from mouse to human cells.

Improvement of Endoscopic Reports with Implementation of a Dictation Template.

AIMS: Completeness of procedure reports is an important quality indicator in endoscopy. A dictation template was developed to ensure key elements were included in colonoscopy and esophagogastroduodenoscopy (EGD) reports. Endoscopy reports were reviewed prior to and following implementation of the dictation templates to determine whether report completeness improved. METHODS: Key elements in an endoscopic report were identified from published guidelines and posted at dictation stations. Colonoscopy and EGD reports were reviewed for the nine physicians performing endoscopy at St. Paul's Hospital prior to and following implementation of dictation templates. Dictation completeness was defined as inclusion of all key elements. Dictation completeness and inclusion of individual key elements at the two time points were compared using the t-test and Chi-square test. RESULTS: Reports for 4648 procedures undertaken by nine endoscopists were reviewed for completeness at each time point (2008 and 2014). Colonoscopy report completeness increased from 65.8% to 83.2% (P < 0.001). Items that improved included documentation of consent, endoscope used, complications, withdrawal time and rectal retroflexion. EGD report completeness increased from 72.7% to 77.3% (P < 0.001) with improvement in documentation of consent and complications. Items consistently underreported for colonoscopy and EGD at both time points included: patient age, comorbidities, current medications and patient comfort. CONCLUSION: There was an association between the use of a posted dictation template at dictation stations and the improved completeness of endoscopic reports.

Internet-Based Patient Education Prior to Colonoscopy: Prospective, Observational Study of a Single Center's Implementation, with Objective Assessment of Bowel Preparation Quality and Patient Satisfaction.

BACKGROUND: Nonpharmacologic factors, including patient education, affect bowel preparation for colonoscopy. Optimal cleansing increases quality and reduces repeat procedures. This study prospectively analyzes use of an individualized online patient education module in place of traditional patient education. AIMS: To determine the effectiveness of online education for patients, measured by the proportion achieving sufficient bowel preparation. Secondary measures include assessment of patient satisfaction. METHODS: Prospective, single-center, observational study. Adults aged 19 years and over, with an e-mail account, scheduled for nonurgent colonoscopy, with English proficiency (or someone who could translate for them) were recruited. Demographics and objective bowel preparation quality were collected. Patient satisfaction was assessed via survey to assess clarity and usefulness of the module. RESULTS: Nine hundred consecutive patients completed the study. 84.6% of patients achieved adequate bowel preparation as measured by Boston bowel preparation score ≥ 6 and 90.1% scored adequately using Ottawa bowel preparation score ≤7. 94.2% and 92.1% of patients rated the web-education module as 'very useful' and 'very clear', respectively (≥8/10 on respective scales). CONCLUSIONS: Our analysis suggests that internet-based patient education prior to colonoscopy is a viable option and achieves adequate bowel preparation. Preparation quality is comparable to previously published trials. Included patients found the process clear and useful. Pragmatic benefits of a web-based protocol such as time and cost savings were not formally assessed but may contribute to greater satisfaction for endoscopists and patients.

Mycalolide B dissociates dynactin and abolishes retrograde axonal transport of dense-core vesicles.

Axonal transport is critical for maintaining synaptic transmission. Of interest, anterograde and retrograde axonal transport appear to be interdependent, as perturbing one directional motor often impairs movement in the opposite direction. Here live imaging of Drosophila and hippocampal neuron dense-core vesicles (DCVs) containing a neuropeptide or brain-derived neurotrophic factor shows that the F-actin depolymerizing macrolide toxin mycalolide B (MB) rapidly and selectively abolishes retrograde, but not anterograde, transport in the axon and the nerve terminal. Latrunculin A does not mimic MB, demonstrating that F-actin depolymerization is not responsible for unidirectional transport inhibition. Given that dynactin initiates retrograde transport and that amino acid sequences implicated in macrolide toxin binding are found in the dynactin component actin-related protein 1, we examined dynactin integrity. Remarkably, cell extract and purified protein experiments show that MB induces disassembly of the dynactin complex. Thus imaging selective retrograde transport inhibition led to the discovery of a small-molecule dynactin disruptor. The rapid unidirectional inhibition by MB suggests that dynactin is absolutely required for retrograde DCV transport but does not directly facilitate ongoing anterograde DCV transport in the axon or nerve terminal. More generally, MB's effects bolster the conclusion that anterograde and retrograde axonal transport are not necessarily interdependent.

Amyloid-ß oligomers induce tau-independent disruption of BDNF axonal transport via calcineurin activation in cultured hippocampal neurons.

Disruption of fast axonal transport (FAT) is an early pathological event in Alzheimer's disease (AD). Soluble amyloid-ß oligomers (AßOs), increasingly recognized as proximal neurotoxins in AD, impair organelle transport in cultured neurons and transgenic mouse models. AßOs also stimulate hyperphosphorylation of the axonal microtubule-associated protein, tau. However, the role of tau in FAT disruption is controversial. Here we show that AßOs reduce vesicular transport of brain-derived neurotrophic factor (BDNF) in hippocampal neurons from both wild-type and tau-knockout mice, indicating that tau is not required for transport disruption. FAT inhibition is not accompanied by microtubule destabilization or neuronal death. Significantly, inhibition of calcineurin (CaN), a calcium-dependent phosphatase implicated in AD pathogenesis, rescues BDNF transport. Moreover, inhibition of protein phosphatase 1 and glycogen synthase kinase 3ß, downstream targets of CaN, prevents BDNF transport defects induced by AßOs. We further show that AßOs induce CaN activation through nonexcitotoxic calcium signaling. Results implicate CaN in FAT regulation and demonstrate that tau is not required for AßO-induced BDNF transport disruption.