Publications by authors named "Charles O'Brien"

The rise of angiosperms to ecological dominance and the breakup of Gondwana during the Mesozoic marked major transitions in the evolutionary history of insect-plant interactions. To elucidate how contemporary trophic interactions were influenced by host plant shifts and palaeogeographical events, we integrated molecular data with information from the fossil record to construct a time tree for ancient phytophagous weevils of the beetle family Belidae. Our analyses indicate that crown-group Belidae originated approximately 138 Ma ago in Gondwana, associated with Pinopsida (conifer) host plants, with larvae likely developing in dead/decaying branches.

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Osteogenesis imperfecta (OI) constitutes a family of bone fragility disorders characterized by both genetic and clinical heterogeneity. Several different mouse models reproduce the classic features of OI, and the most commonly studied carry either a spontaneous or genetically induced pathogenic variant in the Col1a1 or Col1a2 gene. When OI is caused by primary alterations of type I collagen, it represents a systemic connective tissue disease that, in addition to the skeleton, also affects several extra-skeletal tissues and organs, such as skin, teeth, lung, heart, and others, where the altered type I collagen is also expressed.

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Article Synopsis
  • Sperm production requires effective communication between Sertoli cells and germ cells, and researchers studied how RANKL activity in Sertoli cells affects this process.
  • They found that using the RANKL inhibitor denosumab led to increased testicular weight and germ cell growth in testis cultures and a specific mouse model.
  • In a clinical trial, while denosumab didn't improve overall semen quality, it did increase sperm concentration in infertile men with higher levels of anti-müllerian hormone (AMH), indicating a potential targeted treatment approach for male infertility based on AMH levels.
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Breast cancer bone metastases increase fracture risk and are a major cause of morbidity and mortality among women. Upon colonization by tumor cells, the bone microenvironment undergoes profound reprogramming to support cancer progression, which disrupts the balance between osteoclasts and osteoblasts and leads to bone lesions. A deeper understanding of the processes mediating this reprogramming could help develop interventions for treating patients with bone metastases.

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Staphylococcus aureus osteomyelitis leads to extensive bone destruction. Osteoclasts are bone resorbing cells that are often increased in bone infected with S. aureus.

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Breast cancer bone metastases increase fracture risk and are a major cause of morbidity and mortality among women. Upon colonization by tumor cells, the bone microenvironment undergoes profound reprogramming to support cancer progression that disrupts the balance between osteoclasts and osteoblasts, leading to bone lesions. Whether such reprogramming affects matrix-embedded osteocytes remains poorly understood.

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Single-cell RNA-seq has led to novel designations for mesenchymal cells associated with bone as well as multiple designations for what appear to be the same cell type. The main goals of this study were to increase the amount of single-cell RNA sequence data for osteoblasts and osteocytes, to compare cells from the periosteum to those inside bone, and to clarify the major categories of cell types associated with murine bone. We created an atlas of murine bone-associated cells by harmonizing published datasets with in-house data from cells targeted by Osx1-Cre and Dmp1-Cre driver strains.

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Single-cell RNA sequencing has led to numerous novel designations for mesenchymal cell types associated with bone. Consequently, there are now multiple designations for what appear to be the same cell type. In addition, existing datasets contain relatively small numbers of mature osteoblasts and osteocytes and there has been no comparison of periosteal bone cells to those at the endosteum and trabecular bone.

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Denosumab is an anti-RANKL Ab that potently suppresses bone resorption, increases bone mass, and reduces fracture risk. Discontinuation of denosumab causes rapid rebound bone resorption and bone loss, but the molecular mechanisms are unclear. We generated humanized RANKL mice and treated them with denosumab to examine the cellular and molecular conditions associated with rebound resorption.

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Article Synopsis
  • Researchers are exploring cell type-specific loss of function (LOF) studies, often using Cre-mediated recombination, but this method can cause issues by affecting unintended cell types.
  • They developed two new mouse models that enable targeted gene suppression using CRISPR interference (CRISPRi), which is a departure from the traditional recombination-based techniques.
  • The comparison shows that CRISPRi is more effective and precise for cell type-specific LOF than the Cre-loxP system, improving research outcomes in targeted gene studies.
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NAD is an essential co-factor for cellular energy metabolism and multiple other processes. Systemic NAD deficiency has been implicated in skeletal deformities during development in both humans and mice. NAD levels are maintained by multiple synthetic pathways but which ones are important in bone forming cells is unknown.

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Cigarette smoking (CS) and opioid use disorder (OUD) significantly alter brain structure. Although OUD and cigarette smoking are highly comorbid, most prior neuroimaging research in OUD did not control for smoking severity. Specifically, the combined effect of smoking and OUD on the brain gray matter volume (GMV) remains unknown.

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The scavenger receptor class B member 1 (SR-B1 or Scarb1) is a glycosylated cell surface receptor for high density lipoproteins (HDL), oxidized low density lipoproteins (OxLDL), and phosphocholine-containing oxidized phospholipids (PC-OxPLs). Scarb1 is expressed in macrophages and has been shown to have both pro- and anti-atherogenic properties. It has been reported that global deletion of Scarb1 in mice leads to either high or low bone mass and that PC-OxPLs decrease osteoblastogenesis and increase osteoclastogenesis.

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Osteoclasts are multinucleated cells with the unique ability to resorb bone matrix. Excessive production or activation of osteoclasts leads to skeletal pathologies that affect a significant portion of the population. Although therapies that effectively target osteoclasts have been developed, they are associated with sometimes severe side effects, and a fuller understanding of osteoclast biology may lead to more specific treatments.

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The scavenger receptor class B member 1 (SR-B1 or Scarb1) is a cell surface receptor for high density lipoproteins. It also binds oxidized low density lipoproteins and phosphocholine-containing oxidized phospholipids (PC-OxPL), which adversely affect bone homeostasis. Overexpression of a single chain form of the antigen-binding domain of E06 IgM-a natural antibody that recognizes PC-OxPL-increases trabecular and cortical bone mass in female and male mice by stimulating bone formation.

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Opioid use disorder (OUD) is characterized by emotional and cognitive impairements that are associated with poor treatment outcomes. The present study investigated the neural mechanism underlying emotion evaluation and inhibitory control using an affective go/no-go (AGN) task and its association with drug use severity and craving in patients with OUD. Twenty-six recently detoxified patients with OUD underwent functional magnetic resonance imaging (fMRI) while performing the AGN task that required response to frequently presented appetitive stimuli ("go") and inhibition of response to infrequently presented aversive stimuli ("no-go").

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The cytokine RANKL is essential for osteoclast formation during physiological and pathological bone resorption. RANKL also contributes to lymphocyte production, development of lymph nodes and mammary glands, as well as other biological activities. Transcriptional control of the Tnfsf11 gene, which encodes RANKL, is complex and involves distant regulatory regions.

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Article Synopsis
  • Opioid use disorder (OUD) makes people's brains react strongly to things related to opioids, like pictures of drugs.
  • This study used brain scans to see how 29 people with OUD responded to drug-related pictures and checked their cravings and withdrawal symptoms before the tests.
  • The results showed that withdrawal symptoms were key in how the brain reacted to drug cues, indicating that feeling withdrawal can make someone more sensitive to seeing things that remind them of drugs.
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We identified a family with a UMOD gene mutation (C106F) resulting in glomerular inflammation and complement deposition. To determine if the observed phenotype is due to immune system activation by mutant uromodulin, a mouse strain with a homologous cysteine to phenylalanine mutation (C105F) in the UMOD gene was generated using CRISPR-Cas9 gene editing and the effect of this mutation on mononuclear phagocytic cells was examined. Mutant mice developed high levels of intracellular and secreted aggregated uromodulin, resulting in anti-uromodulin antibodies and circulating uromodulin containing immune complexes with glomerular deposition and kidney fibrosis with aging.

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Osteoprotegerin (OPG) inhibits the ability of receptor activator of nuclear factor κB (NF-κB) ligand (RANKL) to stimulate the differentiation, activity, and survival of bone-resorbing osteoclasts. Genetic studies in mice show that osteocytes are an important source of RANKL, but the cellular sources of OPG are unclear. We use conditional deletion of Tnfrsf11b, which encodes OPG, from different cell populations to identify functionally relevant sources of OPG in mice.

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In aging mice, osteoclast number increases in cortical bone but declines in trabecular bone, suggesting that different mechanisms underlie age-associated bone loss in these 2 compartments. Osteocytes produce the osteoclastogenic cytokine RANKL, encoded by Tnfsf11. Tnfsf11 mRNA increases in cortical bone of aged mice, suggesting a mechanism underlying the bone loss.

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There are currently effective Food and Drug Administration (FDA)-approved therapies for alcohol, nicotine, and opioid use disorders. This article will review the development of eight compounds used in the treatment of drug addiction with an emphasis on pharmacological mechanisms and the utility of preclinical animal models of addiction in therapeutic development. In contrast to these successes, animal research has identified a number of promising medications for the treatment of psychostimulant use disorder, none of which have proven to be clinically effective.

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