MiR-124 synergism with ELAVL3 enhances target gene expression to promote neuronal maturity.

Neuron-enriched microRNAs (miRNAs), miR-9/9* and miR-124 (miR-9/9*-124), direct cell fate switching of human fibroblasts to neurons when ectopically expressed by repressing antineurogenic genes. How these miRNAs function after the repression of fibroblast genes for neuronal fate remains unclear. Here, we identified targets of miR-9/9*-124 as reprogramming cells activate the neuronal program and reveal the role of miR-124 that directly promotes the expression of its target genes associated with neuronal development and function. The mode of miR-124 as a positive regulator is determined by the binding of both AGO and a neuron-enriched RNA-binding protein, ELAVL3, to target transcripts. Although existing literature indicates that miRNA-ELAVL family protein interaction can result in either target gene up-regulation or down-regulation in a context-dependent manner, we specifically identified neuronal ELAVL3 as the driver for miR-124 target gene up-regulation in neurons. In primary human neurons, repressing miR-124 and ELAVL3 led to the down-regulation of genes involved in neuronal function and process outgrowth and cellular phenotypes of reduced inward currents and neurite outgrowth. Our results highlight the synergistic role between miR-124 and RNA-binding proteins to promote target gene regulation and neuronal function.

Correlation between operative time and crowd-sourced skills assessment for robotic bariatric surgery.

INTRODUCTION: Operative time has been traditionally used as a proxy for surgical skill and is commonly utilized to measure the learning curve, assuming that faster operations indicate a more skilled surgeon. The Global Evaluative Assessment of Robotic Skills (GEARS) rubric is a validated Likert scale for evaluating technical skill. We hypothesize that operative time will not correlate with the GEARS score. METHODS: Patients undergoing elective robotic sleeve gastrectomy at a single bariatric center of excellence hospital from January 2019 to March 2020 were captured in a prospectively maintained database. For step-specific scoring, videos were broken down into three steps: ligation of short gastric vessels, gastric transection, and oversewing the staple line. Overall and step-specific GEARS scores were assigned by crowd-sourced evaluators. Correlation between operative time and GEARS score was assessed with linear regression and calculation of the R2 statistic. RESULTS: Sixty-eight patients were included in the study, with a mean operative time of 112 ± 27.4 min. The mean GEARS score was 20.1 ± 0.81. Mean scores for the GEARS subcomponents were: bimanual dexterity 4.06 ± 0.17; depth perception 3.96 ± 0.24; efficiency 3.82 ± 0.19; force sensitivity 4.06 ± 0.20; robotic control 4.16 ± 0.21. Operative time and overall score showed no correlation (R2 = 0.0146, p = 0.326). Step-specific times and scores showed weak correlation for gastric transection (R2 = 0.0737, p = 0.028) and no correlation for ligation of short gastric vessels (R2 = 0.0262, p = 0.209) or oversewing the staple line (R2 = 0.0142, p = 0.344). CONCLUSIONS: Operative time and crowd-sourced GEARS score were not correlated. Operative time and GEARS scores measure different performance characteristics, and future studies should consider using both a validated skills assessment tool and operative time for a more complete evaluation of skill.

Medical device active surveillance of spontaneous reports: A literature review of signal detection methods.

PURPOSE: The collection and analysis of real-world data for the active monitoring of medical device performance and safety has become increasingly important. Spontaneous reports, such as those in the Food & Drug Administration's (FDA's) Manufacturer and User Facility Device Experience (MAUDE), provide early warning of potential issues with marketed devices. This review synthesizes the current literature on medical device surveillance signal detection and provides a framework for application of methods to active surveillance of spontaneous reports. METHODS: Ovid MEDLINE, Ovid Embase, Scopus, and PubMed databases were systematically searched up to January 2019. Additionally, five methods articles from pharmacovigilance were added that had potential applications to medical devices. RESULTS: Among 105 articles included, the most common source of data (84%) was registries; median time between data collection and publication was 8 years. Surgical procedure outcome signal detection articles comprised 83% while 14% were on device outcome signal detection. The most common family of methods cited (70%) was Sequential Probability Ratio. CONCLUSION: Application of any signal detection algorithm requires careful consideration of influential factors, data limitations, and algorithmic assumptions. We recommend approaches using disproportionality, statistical process control, and sequential probability tests and provide R packages to further development efforts. The small number of published examples suggest that further development of statistical methods and technological solutions to analyze large amounts of data for device safety and performance is needed. Fundamental differences in products, data infrastructure, and the regulatory landscape suggest that medical device vigilance requires its own body of research distinct from pharmacovigilance.

LONGO: an R package for interactive gene length dependent analysis for neuronal identity.

Motivation: Reprogramming somatic cells into neurons holds great promise to model neuronal development and disease. The efficiency and success rate of neuronal reprogramming, however, may vary between different conversion platforms and cell types, thereby necessitating an unbiased, systematic approach to estimate neuronal identity of converted cells. Recent studies have demonstrated that long genes (>100 kb from transcription start to end) are highly enriched in neurons, which provides an opportunity to identify neurons based on the expression of these long genes. Results: We have developed a versatile R package, LONGO, to analyze gene expression based on gene length. We propose a systematic analysis of long gene expression (LGE) with a metric termed the long gene quotient (LQ) that quantifies LGE in RNA-seq or microarray data to validate neuronal identity at the single-cell and population levels. This unique feature of neurons provides an opportunity to utilize measurements of LGE in transcriptome data to quickly and easily distinguish neurons from non-neuronal cells. By combining this conceptual advancement and statistical tool in a user-friendly and interactive software package, we intend to encourage and simplify further investigation into LGE, particularly as it applies to validating and improving neuronal differentiation and reprogramming methodologies. Availability and implementation: LONGO is freely available for download at https://github.com/biohpc/longo. Supplementary information: Supplementary data are available at Bioinformatics online.

Validation of body mass index (BMI)-related ICD-9-CM and ICD-10-CM administrative diagnosis codes recorded in US claims data.

PURPOSE: To quantify the sensitivity and positive predictive value (PPV) of body mass index (BMI)-related ICD-9-CM and ICD-10-CM diagnosis codes in claims data. METHODS: De-identified electronic health record (EHR) and claims data were obtained from the Optum Integrated Claims-Clinical Database for cross-sections of commercial and Medicare Advantage health plan members age ≥ 20 years in 2013, 2014, and 2016. In each calendar year, health plan members' BMI as coded in the insurance claims data (error-prone measure) was compared with their BMI as recorded in the EHR (gold standard) to estimate the sensitivity and PPV of BMI-related ICD-9-CM and ICD-10-CM diagnosis codes. The unit of analysis was the person-year. RESULTS: The study sample included 746 763 distinct health plan members who contributed 1 116 283 eligible person-years (median age 56 years; 57% female; 65% commercially insured and 35% with Medicare Advantage). BMI-related diagnoses were coded for 14.6%. The sensitivity of BMI-related diagnoses codes for the detection of underweight, normal weight, overweight, and obesity was 10.1%, 3.7%, 6.0%, and 25.2%, and the PPV was 49.0% for underweight, 89.6% for normal weight, 73.4% for overweight, and 92.4% for obesity, respectively. The sensitivity of BMI-related diagnosis codes was higher in the ICD-10-CM era relative to the ICD-9-CM era. CONCLUSIONS: The PPV of BMI-related diagnosis codes for normal weight, overweight, and obesity was high (>70%) but the sensitivity was low (<30%). BMI-related diagnoses were more likely to be coded in patients with class II or III obesity (BMI ≥35 kg/m2 ), and in 2016 relative to 2013 or 2014.

Assessing the real-world effect of laparoscopic bariatric surgery on the management of obesity-related comorbidities: A retrospective matched cohort study using a US Claims Database.

AIMS: To evaluate the real-world effect of laparoscopic bariatric surgery, comprising adjustable gastric banding (LAGB), laparoscopic Roux-en-Y gastric bypass (LRYGB) and laparoscopic sleeve gastrectomy (LSG), on the management of obesity-related comorbidities. METHODS: Patients who underwent laparoscopic bariatric surgeries between 2006 and 2013 were identified from the Optum Clinformatics administrative claims database. Those surgical patients were matched to medically managed patients (controls) on selected patient characteristics. Comorbidity management was assessed every 6 months up to 5 years after the surgery or an assigned index date for control subjects (follow-up), by evaluating the number of medication classes used to treat type 2 diabetes, hypertension and dyslipidaemia, as well as by evaluating the percentages of patients free of medications for these comorbidities. RESULTS: Patients who underwent LAGB (n = 4208, mean age 46.3 years), LRYGB (n = 4308, mean age 46.4 years) or LSG (n = 545, mean age 45.1 years) and patients in the control cohort (n = 9061, mean age 46.4 years) were similar in age, and the majority of patients in each study cohort were female (69.4%-75.8%). Compared with control subjects, patients who had laparoscopic bariatric surgery had significantly lower medication usage for obesity-related comorbidities, a trend that was evident at 6 months and that continued for up to 5 years of follow-up. Sub-analyses of changes in selected laboratory test values over follow-up corroborated the primary analyses. CONCLUSIONS: Patients who had laparoscopic bariatric surgery used fewer medications for type 2 diabetes, hypertension and dyslipidaemia and had significant improvement in cardiometabolic risk factors for up to 5 years of follow-up compared with matched control subjects.

MicroRNA-mediated conversion of human fibroblasts to neurons.

Neurogenic transcription factors and evolutionarily conserved signalling pathways have been found to be instrumental in the formation of neurons. However, the instructive role of microRNAs (miRNAs) in neurogenesis remains unexplored. We recently discovered that miR-9* and miR-124 instruct compositional changes of SWI/SNF-like BAF chromatin-remodelling complexes, a process important for neuronal differentiation and function. Nearing mitotic exit of neural progenitors, miR-9* and miR-124 repress the BAF53a subunit of the neural-progenitor (np)BAF chromatin-remodelling complex. After mitotic exit, BAF53a is replaced by BAF53b, and BAF45a by BAF45b and BAF45c, which are then incorporated into neuron-specific (n)BAF complexes essential for post-mitotic functions. Because miR-9/9* and miR-124 also control multiple genes regulating neuronal differentiation and function, we proposed that these miRNAs might contribute to neuronal fates. Here we show that expression of miR-9/9* and miR-124 (miR-9/9*-124) in human fibroblasts induces their conversion into neurons, a process facilitated by NEUROD2. Further addition of neurogenic transcription factors ASCL1 and MYT1L enhances the rate of conversion and the maturation of the converted neurons, whereas expression of these transcription factors alone without miR-9/9*-124 was ineffective. These studies indicate that the genetic circuitry involving miR-9/9*-124 can have an instructive role in neural fate determination.

Generation of BAF53b-Cre transgenic mice with pan-neuronal Cre activities.

Molecular and functional studies of genes in neurons in mouse models require neuron-specific Cre lines. The current available neuronal Cre transgenic or knock-in lines either result in expression in a subset of neurons or expression in both neuronal and non-neuronal tissues. Previously we identified BAF53b as a neuron-specific subunit of the chromatin remodeling BAF complexes. Using a bacteria artificial chromosome (BAC) construct containing the BAF53b gene, we generated a Cre transgenic mouse under the control of BAF53b regulatory elements. Like the endogenous BAF53b gene, we showed that BAF53b-Cre is largely neuron-specific. In both central and peripheral nervous systems, it was expressed in all developing neurons examined and was not observed in neural progenitors or glial cells. In addition, BAF53b-Cre functioned in primary cultures in a pan-neuron-specific manner. Thus, BAF53b-Cre mice will be a useful genetic tool to manipulate gene expression in developing neurons for molecular, biochemical, and functional studies.

MicroRNA-dependent genetic networks during neural development.

The development of the structurally and functionally diverse mammalian nervous system requires the integration of numerous levels of gene regulation. Accumulating evidence suggests that microRNAs are key mediators of genetic networks during neural development. Importantly, microRNAs are found to regulate both feedback and feedforward loops during neural development leading to large changes in gene expression. These repressive interactions provide an additional mechanism that facilitates the establishment of complexity within the nervous system. Here, we review studies that have enabled the identification of microRNAs enriched in the brain and discuss the way that genetic networks in neural development depend on microRNAs.

MicroRNA-mediated switching of chromatin-remodelling complexes in neural development.

One of the most distinctive steps in the development of the vertebrate nervous system occurs at mitotic exit when cells lose multipotency and begin to develop stable connections that will persist for a lifetime. This transition is accompanied by a switch in ATP-dependent chromatin-remodelling mechanisms that appears to coincide with the final mitotic division of neurons. This switch involves the exchange of the BAF53a (also known as ACTL6a) and BAF45a (PHF10) subunits within Swi/Snf-like neural-progenitor-specific BAF (npBAF) complexes for the homologous BAF53b (ACTL6b) and BAF45b (DPF1) subunits within neuron-specific BAF (nBAF) complexes in post-mitotic neurons. The subunits of the npBAF complex are essential for neural-progenitor proliferation, and mice with reduced dosage for the genes encoding its subunits have defects in neural-tube closure similar to those in human spina bifida, one of the most serious congenital birth defects. In contrast, BAF53b and the nBAF complex are essential for an evolutionarily conserved program of post-mitotic neural development and dendritic morphogenesis. Here we show that this essential transition is mediated by repression of BAF53a by miR-9* and miR-124. We find that BAF53a repression is mediated by sequences in the 3' untranslated region corresponding to the recognition sites for miR-9* and miR-124, which are selectively expressed in post-mitotic neurons. Mutation of these sites led to persistent expression of BAF53a and defective activity-dependent dendritic outgrowth in neurons. In addition, overexpression of miR-9* and miR-124 in neural progenitors caused reduced proliferation. Previous studies have indicated that miR-9* and miR-124 are repressed by the repressor-element-1-silencing transcription factor (REST, also known as NRSF). Indeed, expression of REST in post-mitotic neurons led to derepression of BAF53a, indicating that REST-mediated repression of microRNAs directs the essential switch of chromatin regulatory complexes.

Prospective Clinical Study to Evaluate Clinical Performance of a Powered Surgical Stapler in Video-assisted Thoracoscopic Lung Resections.

Video-assisted thoracic surgery (VATS) research often focuses on postoperative air leak, with special consideration for prolonged air leak. There is limited clinical data regarding how stapling devices might affect performance and postoperative outcomes, including air leak. This prospective research evaluates intraoperative and postoperative data associated with VATS, using a new surgical stapling device, in two different geographic regions (the U.S. and Europe). A total of 226 subjects across 10 institutions were enrolled in this study. The primary endpoint was occurrence and duration of postoperative air leaks, including prolonged air leak. Additional data collected included intraoperative details and postoperative outcomes. Prolonged air leak occurred in 22 subjects (10.3%) across procedures (152 lobectomies, 63 wedge resections, and 11 occurrences of wedge resection plus lobectomy). There were no significant differences in occurrence or duration of PAL between the U.S. and Europe. Regional differences were observed for intraoperative leak testing and cartridge selection relative to tissue type. Despite differences in surgical technique between continents, no major or significant difference in air leak or other clinical outcome was detected. Additional research is needed to characterize optimal cartridge selection to tissue properties and how these may potentially impact clinical outcomes.

Kinetic analysis of npBAF to nBAF switching reveals exchange of SS18 with CREST and integration with neural developmental pathways.

During the development of the vertebrate nervous system, neural progenitors divide, generate progeny that exit mitosis, and then migrate to sites where they elaborate specific morphologies and synaptic connections. Mitotic exit in neurons is accompanied by an essential switch in ATP-dependent chromatin regulatory complexes from the neural progenitor Brg/Brm-associated factor (npBAF) to neuron-specific nBAF complexes that is in part driven by miR-9/9* and miR-124. Recapitulating this microRNA/chromatin switch in fibroblasts leads to their direct conversion to neurons. We have defined the kinetics of neuron-specific BAF complex assembly in the formation of induced neurons from mouse embryonic stem cells, human fibroblasts, and normal mouse neural differentiation and, using proteomic analysis, found that this switch also includes the removal of SS18 and its replacement by CREST at mitotic exit. We found that switching of chromatin remodeling mechanisms is highly correlated with a broad switch in the use of neurogenic transcription factors. Knock-down of SS18 in neural stem cells causes cell-cycle exit and failure to self-renew, whereas continued expression of SS18 in neurons blocks dendritic outgrowth, underlining the importance of subunit switching. Because dominant mutations in BAF subunits underlie widely different human neurologic diseases arising in different neuronal types, our studies suggest that the characteristics of these diseases must be interpreted in the context of the different BAF assemblies in neurons rather than a singular mammalian SWItch/sucrose nonfermentable (mSWI/SNF) complex.

Notch Inhibition Enhances Morphological Reprogramming of microRNA-Induced Human Neurons.

Although the importance of Notch signaling in brain development is well-known, its specific contribution to cellular reprogramming remains less defined. Here, we use microRNA-induced neurons that are directly reprogrammed from human fibroblasts to determine how Notch signaling contributes to neuronal identity. We found that inhibiting Notch signaling led to an increase in neurite extension, while activating Notch signaling had the opposite effect. Surprisingly, Notch inhibition during the first week of reprogramming was both necessary and sufficient to enhance neurite outgrowth at a later timepoint. This timeframe is when the reprogramming miRNAs, miR-9/9* and miR-124, primarily induce a post-mitotic state and erase fibroblast identity. Accordingly, transcriptomic analysis showed that the effect of Notch inhibition was likely due to improvements in fibroblast fate erasure and silencing of anti-neuronal genes. To this effect, we identify MYLIP , whose downregulation in response to Notch inhibition significantly promoted neurite outgrowth. Moreover, Notch inhibition resulted in cells with neuronal transcriptome signature defined by expressing long genes at a faster rate than the control, demonstrating the effect of accelerated fate erasure on neuronal fate acquisition. Our results demonstrate the critical role of Notch signaling in mediating morphological changes in miRNA-based neuronal reprogramming of human adult fibroblasts.

An interpretable machine learning-based cerebrospinal fluid proteomics clock for predicting age reveals novel insights into brain aging.

Machine learning can be used to create "biologic clocks" that predict age. However, organs, tissues, and biofluids may age at different rates from the organism as a whole. We sought to understand how cerebrospinal fluid (CSF) changes with age to inform the development of brain aging-related disease mechanisms and identify potential anti-aging therapeutic targets. Several epigenetic clocks exist based on plasma and neuronal tissues; however, plasma may not reflect brain aging specifically and tissue-based clocks require samples that are difficult to obtain from living participants. To address these problems, we developed a machine learning clock that uses CSF proteomics to predict the chronological age of individuals with a 0.79 Pearson correlation and mean estimated error (MAE) of 4.30 years in our validation cohort. Additionally, we analyzed proteins highly weighted by the algorithm to gain insights into changes in CSF and uncover novel insights into brain aging. We also demonstrate a novel method to create a minimal protein clock that uses just 109 protein features from the original clock to achieve a similar accuracy (0.75 correlation, MAE 5.41). Finally, we demonstrate that our clock identifies novel proteins that are highly predictive of age in interactions with other proteins, but do not directly correlate with chronological age themselves. In conclusion, we propose that our CSF protein aging clock can identify novel proteins that influence the rate of aging of the central nervous system (CNS), in a manner that would not be identifiable by examining their individual relationships with age.

Is suture-based cerclage biomechanically superior to traditional metallic cerclage for fixation of periprosthetic femoral fractures: A matched pair cadaveric study.

BACKGROUND: While traditional metallic cerclage remains the primary method in clinical application, non-metallic cerclage systems have recently gained popularity due to low risks of soft tissue irritation and bone intrusion. The objective of this study was to assess the performance of a novel non-metallic suture-based cerclage in comparison to traditional metallic cerclage cables for fixation of periprosthetic femoral fractures. METHODS: An extended trochanteric osteotomy was performed on eight pairs of cadaveric femora, followed by reduction using either metallic cerclages (Group I) or the suture-based cerclage (Group II). A modular tapered fluted stem was then implanted in each specimen. The fragment translation during canal preparation and stem implantation was quantified using laser-scanning. Subsequently, each specimen underwent 500 cycles of multiaxial loading, with fragment translation and stem subsidence measured using a motion capture system. FINDINGS: Following stem implantation, specimens in Group II exhibited a significantly greater lateral fragment translation (466 µm vs 754 µm, p = 0.017). However, there were no significant differences in anterior and distal translation between groups (p > 0.05). During multiaxial loading, the average stem subsidence in Group I was 0.36 mm (range, 0.04-1.42 mm), compared to 0.41 mm (range, 0.03-1.29) in Group II (p > 0.05). No significant difference was found in fragment translations between the two groups (p > 0.05). INTERPRETATION: The suture-based cerclage system exhibited comparable biomechanical performance in fixation stability to conventional metallic cerclage cables. Yet, it was associated with a larger residual lateral gap between the fragments following stem implantation. Ultimately, the choice of fixation method should account for multiple factors, including patient characteristics, surgeon preference, and bone quality.

SAK3 confers neuroprotection in the neurodegeneration model of X-linked Dystonia-Parkinsonism.

Background X-linked Dystonia-Parkinsonism(XDP) is an adult-onset neurodegenerative disorder that results in the loss of striatal medium spiny neurons (MSNs). XDP is associated with disease-specific mutations in and around the TAF1 gene. This study highlights the utility of directly reprogrammed MSNs from fibroblasts of affected XDP individuals as a platform that captures cellular and epigenetic phenotypes associated with XDP-related neurodegeneration. In addition, the current study demonstrates the neuroprotective effect of SAK3 currently tested in other neurodegenerative diseases. Methods XDP fibroblasts from three independent patients as well as age- and sex-matched control fibroblasts were used to generate MSNs by direct neuronal reprogramming using miRNA-9/9*-124 and thetranscription factors CTIP2 , DLX1 -P2A- DLX2 , and MYT1L . Neuronal death, DNA damage, and mitochondrial health assays were carried out to assess the neurodegenerative state of directly reprogrammed MSNs from XDP patients (XDP-MSNs). RNA sequencing and ATAC sequencing were performed to infer changes in the transcriptomic and chromatin landscapesof XDP-MSNs compared to those of control MSNs (Ctrl-MSNs). Results Our results show that XDP patient fibroblasts can be successfully reprogrammed into MSNs and XDP-MSNs display several degenerative phenotypes, including neuronal death, DNA damage, and mitochondrial dysfunction, compared to Ctrl-MSNs reprogrammed from age- and sex-matched control individuals' fibroblasts. In addition, XDP-MSNs showed increased vulnerability to TNFα -toxicity compared to Ctrl-MSNs. To dissect the altered cellular state in XDP-MSNs, we conducted transcriptomic and chromatin accessibility analyses using RNA- and ATAC-seq. Our results indicate that pathways related to neuronal function, calcium signaling, and genes related to other neurodegenerative diseases are commonly altered in XDP-MSNs from multiple patients. Interestingly, we found that SAK3, a T-type calcium channel activator, that may have therapeutic values in other neurodegenerative disorders, protected XDP-MSNs from neuronal death. Notably, we found that SAK3-mediated alleviation of neurodegeneration in XDP-MSNs was accompanied by gene expression changes toward Ctrl-MSNs.

Longitudinal modeling of human neuronal aging reveals the contribution of the RCAN1-TFEB pathway to Huntington's disease neurodegeneration.

Aging is a common risk factor in neurodegenerative disorders. Investigating neuronal aging in an isogenic background stands to facilitate analysis of the interplay between neuronal aging and neurodegeneration. Here we perform direct neuronal reprogramming of longitudinally collected human fibroblasts to reveal genetic pathways altered at different ages. Comparative transcriptome analysis of longitudinally aged striatal medium spiny neurons (MSNs) in Huntington's disease identified pathways involving RCAN1, a negative regulator of calcineurin. Notably, RCAN1 protein increased with age in reprogrammed MSNs as well as in human postmortem striatum and RCAN1 knockdown rescued patient-derived MSNs of Huntington's disease from degeneration. RCAN1 knockdown enhanced chromatin accessibility of genes involved in longevity and autophagy, mediated through enhanced calcineurin activity, leading to TFEB's nuclear localization by dephosphorylation. Furthermore, G2-115, an analog of glibenclamide with autophagy-enhancing activities, reduced the RCAN1-calcineurin interaction, phenocopying the effect of RCAN1 knockdown. Our results demonstrate that targeting RCAN1 genetically or pharmacologically can increase neuronal resilience in Huntington's disease.

Multi-omic analysis of Huntington's disease reveals a compensatory astrocyte state.

The mechanisms underlying the selective regional vulnerability to neurodegeneration in Huntington's disease (HD) have not been fully defined. To explore the role of astrocytes in this phenomenon, we used single-nucleus and bulk RNAseq, lipidomics, HTT gene CAG repeat-length measurements, and multiplexed immunofluorescence on HD and control post-mortem brains. We identified genes that correlated with CAG repeat length, which were enriched in astrocyte genes, and lipidomic signatures that implicated poly-unsaturated fatty acids in sensitizing neurons to cell death. Because astrocytes play essential roles in lipid metabolism, we explored the heterogeneity of astrocytic states in both protoplasmic and fibrous-like (CD44+) astrocytes. Significantly, one protoplasmic astrocyte state showed high levels of metallothioneins and was correlated with the selective vulnerability of distinct striatal neuronal populations. When modeled in vitro, this state improved the viability of HD-patient-derived spiny projection neurons. Our findings uncover key roles of astrocytic states in protecting against neurodegeneration in HD.

Modeling late-onset Alzheimer's disease neuropathology via direct neuronal reprogramming.

Late-onset Alzheimer's disease (LOAD) is the most common form of Alzheimer's disease (AD). However, modeling sporadic LOAD that endogenously captures hallmark neuronal pathologies such as amyloid-ß (Aß) deposition, tau tangles, and neuronal loss remains an unmet need. We demonstrate that neurons generated by microRNA (miRNA)-based direct reprogramming of fibroblasts from individuals affected by autosomal dominant AD (ADAD) and LOAD in a three-dimensional environment effectively recapitulate key neuropathological features of AD. Reprogrammed LOAD neurons exhibit Aß-dependent neurodegeneration, and treatment with ß- or γ-secretase inhibitors before (but not subsequent to) Aß deposit formation mitigated neuronal death. Moreover inhibiting age-associated retrotransposable elements in LOAD neurons reduced both Aß deposition and neurodegeneration. Our study underscores the efficacy of modeling late-onset neuropathology of LOAD through high-efficiency miRNA-based neuronal reprogramming.