Publications by authors named "Levi B"

Somatic activating mutations in KRAS can cause complex lymphatic anomalies (CLAs). However, the specific processes that drive KRAS-mediated CLAs have yet to be fully elucidated. Here, we used single-cell RNA sequencing to construct an atlas of normal and KrasG12D-malformed lymphatic vessels.

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Adeno-associated viruses (AAVs) have emerged as the foremost gene therapy delivery vehicles due to their versatility, durability, and safety profile. Here we demonstrate extensive chimerism, manifesting as pervasive barcode swapping, among complex AAV libraries that are packaged as a pool. The observed chimerism is length- and homology-dependent but capsid-independent, in some cases affecting the majority of packaged AAV genomes.

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-acting regulatory enhancer elements are valuable tools for gaining cell type-specific genetic access. Leveraging large chromatin accessibility atlases, putative enhancer sequences can be identified and deployed in adeno-associated virus (AAV) delivery platforms. However, a significant bottleneck in enhancer AAV discovery is charting their detailed expression patterns , a process that currently requires gold-standard one-by-one testing.

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Physician databases constitute an essential component of health workforce planning. However, while some countries have established functioning national physician databases, others have failed to do so. We compared the healthcare systems of two technologically and economically developed countries, Canada and Israel, which represent cases of respective success and failure in establishing physician databases.

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The mammalian cortex is composed of a highly diverse set of cell types and develops through a series of temporally regulated events that build out the cell type and circuit foundation for cortical function. The mechanisms underlying the development of different cell types remain elusive. Single-cell transcriptomics provides the capacity to systematically study cell types across the entire temporal range of cortical development.

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Article Synopsis
  • Biological aging involves a gradual loss of homeostasis in molecular and cellular functions, particularly in the brain, which contains diverse cell types that differ in their aging resilience.
  • This study offers an extensive single-cell RNA sequencing dataset of approximately 1.2 million transcriptomes from brain cells in young and aged mice, identifying 847 cell clusters and 14 age-biased clusters predominantly involving glial types.
  • Key findings reveal specific gene expression changes with aging, including decreased neuronal function genes and increased immune-related genes, particularly in cells around the third ventricle of the hypothalamus, suggesting its critical role in the aging process of the mouse brain.
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Health and racial disparities can limit access to preventative, trauma, and chronic disease care but have not been addressed in burn resuscitation. Over- and under-resuscitation contribute to increased overall hospital costs, and morbidity and mortality rates. The primary objective of this study was to identify potential racial disparities that may exist during the initial fluid resuscitation after burn injury.

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Recent studies have linked pain and the resultant nociception-induced neural inflammation (NINI) to trauma-induced heterotopic ossification (THO). It is postulated that nociception at the injury site stimulates the transient receptor potential vanilloid-1 (the transient receptor potential cation channel subfamily V member 1) receptors on sensory nerves within the injured tissues resulting in the expression of neuroinflammatory peptides, substance P (SP), and calcitonin gene-related peptide (CGRP). Additionally, BMP-2 released from fractured bones and soft tissue injury also selectively activates TRVP1 receptors, resulting in the release of SP and CGRP and causing neuroinflammation and degranulation of mast cells causing the breakdown the blood-nerve barrier (BNB), leading to release of neural crest derived progenitor cells (NCDPCs) into the injured tissue.

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Alzheimer's disease (AD) is the leading cause of dementia in older adults. Although AD progression is characterized by stereotyped accumulation of proteinopathies, the affected cellular populations remain understudied. Here we use multiomics, spatial genomics and reference atlases from the BRAIN Initiative to study middle temporal gyrus cell types in 84 donors with varying AD pathologies.

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We present an enhancer AAV toolbox for accessing and perturbing striatal cell types and circuits. Best-in-class vectors were curated for accessing major striatal neuron populations including medium spiny neurons (MSNs), direct and indirect pathway MSNs, as well as Sst-Chodl, Pvalb-Pthlh, and cholinergic interneurons. Specificity was evaluated by multiple modes of molecular validation, three different routes of virus delivery, and with diverse transgene cargos.

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Heterotopic ossification (HO) is a pathological process that commonly arises following severe polytrauma, characterized by the anomalous differentiation of mesenchymal progenitor cells and resulting in the formation of ectopic bone in non-skeletal tissues. This abnormal bone growth contributes to pain and reduced mobility, especially when adjacent to a joint. Our prior observations suggested an essential role of NGF (Nerve Growth Factor)-responsive TrkA (Tropomyosin Receptor Kinase A)-expressing peripheral nerves in regulating abnormal osteochondral differentiation following tendon injury.

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Article Synopsis
  • Burn depth determination is essential for effective patient care, but current methods lack precision; however, recent animal studies revealed that Short Wave Infrared (SWIR) imaging can effectively differentiate between superficial and deep burns.
  • A study involving 11 patients utilized a SWIR assessment tool (SWAT) to compare reflectance of multiple SWIR bands with surgeons' classifications and histology results to evaluate burn depths.
  • The findings indicate that while reflectance changes at certain wavelengths correlate with burn depth, multi-spectral imaging through SWAT may offer improved accuracy in assessing burn wound severity.
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  • Identifying cell type-specific enhancers in the brain is crucial for developing genetic tools to study mammalian brains, particularly in the context of mouse models.
  • The 'Brain Initiative Cell Census Network (BICCN) Challenge' aimed to evaluate machine learning methods for predicting these enhancers based on data from multi-omics studies.
  • Key findings included the importance of open chromatin as a predictor of functional enhancers, the role of sequence models in distinguishing non-functional enhancers, and the recognition of specific transcription factor codes to aid in the design of enhancers, ultimately advancing our understanding of gene regulation in the mammalian brain.
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  • Researchers addressed the limited access to lower motor neurons (LMNs) in the mammalian spinal cord by creating single cell multiome datasets from mouse and macaque spinal cords to identify enhancers for different neuronal populations.* -
  • They cloned identified enhancers into viral vectors and conducted functional tests in mice to screen for effective candidates, which were then validated in rats and macaques.* -
  • This new toolkit for labeling LMNs and upper motor neurons (UMNs) can facilitate future research on cell function across species and contribute to potential therapies for neurodegenerative diseases in humans.*
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Background: Despite the widespread use of humor in social interactions and the considerable literature on humor in multiple fields of study, the use of humor in parenting has received very little formal study. The purpose of this pilot study was to gather preliminary data on the use of humor in the raising of children.

Materials And Methods: We developed and administered a 10-item survey to measure people's experiences being raised with humor and their views regarding humor as a parenting tool.

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Proactive esophageal cooling for the purpose of reducing the likelihood of ablation-related esophageal injury resulting from radiofrequency (RF) cardiac ablation procedures is increasingly being used and has been Food and Drug Administration cleared as a protective strategy during left atrial RF ablation for the treatment of atrial fibrillation. In this review, we examine the evidence supporting the use of proactive esophageal cooling and the potential mechanisms of action that reduce the likelihood of atrioesophageal fistula (AEF) formation. Although the pathophysiology behind AEF formation after thermal injury from RF ablation is not well studied, a robust literature on fistula formation in other conditions (eg, Crohn disease, cancer, and trauma) exists and the relationship to AEF formation is investigated in this review.

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Bone pain is a presenting feature of bone cancers such as osteosarcoma (OS), relayed by skeletal-innervating peripheral afferent neurons. Potential functions of tumor-associated sensory neurons in bone cancers beyond pain sensation are unknown. To uncover neural regulatory functions, a chemical-genetic approach in mice with a knock-in allele for TrkA was used to functionally perturb sensory nerve innervation during OS growth and disease progression.

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Article Synopsis
  • The mammalian cortex consists of different cell types that have specific properties, which are important for understanding how the cortex functions in both health and disease.
  • Researchers utilized data from mouse and human studies to identify marker genes and enhancers for various cortical cell types, creating a comprehensive set of tools for targeting these cells specifically.
  • They introduced fifteen new transgenic driver lines, two new reporter lines, and over 800 enhancer AAVs, facilitating a wide range of experimental approaches to study the mammalian cortex and its functions.
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Beyond the sensation of pain, peripheral nerves have been shown to play crucial roles in tissue regeneration and repair. As a highly innervated organ, bone can recover from injury without scar formation, making it an interesting model in which to study the role of nerves in tissue regeneration. As a comparison, tendon is a musculoskeletal tissue that is hypo-innervated, with repair often resulting in scar formation.

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Radiation therapy is a clinically proven, localized preventive measure for heterotopic ossification (HO). Despite its efficacy, there is a lack of standardization of radiation prescription dosing and fractionation, and the mechanism of the impact of radiation in HO prevention remains unknown. Here, using an established mouse model of traumatic HO induced by burn and tenotomy, we demonstrate that 7Gy in one fraction delivered to the injury site within 72 hours postoperatively significantly decreases HO formation and improves hindlimb range of motion.

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Background: The ketogenic diet (KD), based on high fat (over 70% of daily calories), low carbohydrate, and adequate protein intake, has become popular due to its potential therapeutic benefits for several diseases including cancer. Under KD and starvation conditions, the lack of carbohydrates promotes the production of ketone bodies (KB) from fats by the liver as an alternative source of metabolic energy. KD and starvation may affect the metabolism in cancer cells, as well as tumor characteristics.

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Autografting with split-thickness skin grafts (STSG) remains an essential procedure in burn and reconstructive surgery. The process of harvesting STSG, however, leaves behind a donor site, an exposed area of partial-thickness dermis left to heal by secondary intention. There has yet to be a consensus amongst surgeons regarding optimal management of the donor site.

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Heterotopic ossification (HO) is a challenging condition that occurs after musculoskeletal injury and is characterized by the formation of bone in non-skeletal tissues. While the effect of HO on blood vessels is well established, little is known about its impact on lymphatic vessels. Here, we use a mouse model of traumatic HO to investigate the relationship between HO and lymphatic vessels.

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Heterotopic ossification (HO) is a debilitating pathology where ectopic bone develops in areas of soft tissue. HO can develop as a consequence of traumatic insult or as a result of dysregulated osteogenic signaling, as in the case of the orphan disease fibrodysplasia ossificans progressiva (FOP). Traumatic HO (tHO) formation is mediated by the complex interplay of signaling between progenitor, inflammatory, and nerve cells, among others, making it a challenging process to understand.

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