Acute promyelocytic leukemia with torque teno mini virus (TTMV)::RARA fusion: an approach to screening and diagnosis.

Acute promyelocytic leukemia (APL) with variant RARA translocation is linked to over 15 partner genes. Recent publications encompassing six cases have expanded the spectrum of RARA partners to torque teno mini virus (TTMV). This entity is likely under-recognized due to lack of clinician and pathologist familiarity, inability to detect the fusion using routine testing modalities, and informatic challenges in its recognition within next-generation sequencing (NGS) data. We describe a clinicopathologic approach and provide necessary tools to screen and diagnose APL with TTMV::RARA using existing clinical DNA or RNA-based NGS assays, which led to identification of four cases, all without other known cytogenetic/molecular drivers. One was identified prospectively and three retrospectively, including two from custom automated screening of multiple data sets (50 257 cases of hematopoietic malignancy, including 4809 acute myeloid leukemia (AML)/myeloid sarcoma/APL cases). Two cases presented as myeloid sarcoma, including one with multiple relapses after AML-type chemotherapy and hematopoietic stem cell transplant (HSCT). Two cases presented as leukemia, had a poor response to induction chemotherapy, but achieved remission upon re-induction (including all-trans retinoic acid (ATRA) in one case) and subsequent HSCT. Neoplastic cells demonstrated features of APL including frequent azurophilic granules and dim/absent CD34 and HLA-DR expression. RARA rearrangement was not detected by karyotype or FISH. Custom analysis of NGS fusion panel data identified TTMV::RARA rearrangements, and in the prospectively identified case, facilitated monitoring in sequential bone marrow samples. APL with TTMV::RARA is a rare leukemia with a high rate of treatment failure in described cases. The diagnosis should be considered in leukemias with features of APL that lack detectable RARA fusions and other drivers, and may be confirmed by appropriate NGS tests with custom informatics. Incorporation of ATRA may have a role in treatment but requires accurate recognition of the fusion for appropriate classification as APL.

Identification of the NRF2 transcriptional network as a therapeutic target for trigeminal neuropathic pain.

Trigeminal neuralgia, historically dubbed the "suicide disease," is an exceedingly painful neurologic condition characterized by sudden episodes of intense facial pain. Unfortunately, the only U.S. Food and Drug Administration (FDA)-approved medication for trigeminal neuralgia carries substantial side effects, with many patients requiring surgery. Here, we identify the NRF2 transcriptional network as a potential therapeutic target. We report that cerebrospinal fluid from patients with trigeminal neuralgia accumulates reactive oxygen species, several of which directly activate the pain-transducing channel TRPA1. Similar to our patient cohort, a mouse model of trigeminal neuropathic pain also exhibits notable oxidative stress. We discover that stimulating the NRF2 antioxidant transcriptional network is as analgesic as inhibiting TRPA1, in part by reversing the underlying oxidative stress. Using a transcriptome-guided drug discovery strategy, we identify two NRF2 network modulators as potential treatments. One of these candidates, exemestane, is already FDA-approved and may thus be a promising alternative treatment for trigeminal neuropathic pain.

A genome-wide view of the de-differentiation of central nervous system endothelial cells in culture.

Vascular endothelial cells (ECs) derived from the central nervous system (CNS) variably lose their unique barrier properties during in vitro culture, hindering the development of robust assays for blood-brain barrier (BBB) function, including drug permeability and extrusion assays. In previous work (Sabbagh et al., 2018) we characterized transcriptional and accessible chromatin landscapes of acutely isolated mouse CNS ECs. In this report, we compare transcriptional and accessible chromatin landscapes of acutely isolated mouse CNS ECs versus mouse CNS ECs in short-term in vitro culture. We observe that standard culture conditions are associated with a rapid and selective loss of BBB transcripts and chromatin features, as well as a greatly reduced level of beta-catenin signaling. Interestingly, forced expression of a stabilized derivative of beta-catenin, which in vivo leads to a partial conversion of non-BBB CNS ECs to a BBB-like state, has little or no effect on gene expression or chromatin accessibility in vitro.

Activation of Mast-Cell-Expressed Mas-Related G-Protein-Coupled Receptors Drives Non-histaminergic Itch.

Classical itch studies have focused on immunoglobulin E (IgE)-mediated mast cell activation and histamine release. Recently, members of the Mas-related G-protein-coupled receptor (Mrgpr) family have been identified as mast cell receptors, but their role in itch is unclear. Here, we report that mast cell activation via Mrgprb2 evoked non-histaminergic itch in mice independently of the IgE-Fc epsilon RI (FcεRI)-histamine axis. Compared with IgE-FcεRI stimulation, Mrgprb2 activation of mast cells was distinct in both released substances (histamine, serotonin, and tryptase) and the pattern of activated itch-sensory neurons. Mrgprb2 deficiency decreased itch in multiple preclinical models of allergic contact dermatitis (ACD), a pruritic inflammatory skin disorder, and both mast cell number and PAMP1-20 concentrations (agonist of the human Mrgprb2 homolog, MRGPRX2) were increased in human ACD skin. These findings suggest that this pathway may represent a therapeutic target for treating ACD and mast-cell-associated itch disorders in which antihistamines are ineffective.

Beta-catenin signaling regulates barrier-specific gene expression in circumventricular organ and ocular vasculatures.

The brain, spinal cord, and retina are supplied by capillaries that do not permit free diffusion of molecules between serum and parenchyma, a property that defines the blood-brain and blood-retina barriers. Exceptions to this pattern are found in circumventricular organs (CVOs), small midline brain structures that are supplied by high permeability capillaries. In the eye and brain, high permeability capillaries are also present in the choriocapillaris, which supplies the retinal pigment epithelium and photoreceptors, and the ciliary body and choroid plexus, the sources of aqueous humor and cerebrospinal fluid, respectively. We show here that (1) endothelial cells in these high permeability vascular systems have very low beta-catenin signaling compared to barrier-competent endothelial cells, and (2) elevating beta-catenin signaling leads to a partial conversion of permeable endothelial cells to a barrier-type state. In one CVO, the area postrema, high permeability is maintained, in part, by local production of Wnt inhibitory factor-1.

Affinity capture of polyribosomes followed by RNAseq (ACAPseq), a discovery platform for protein-protein interactions.

Defining protein-protein interactions (PPIs) is central to the biological sciences. Here, we present a novel platform - Affinity Capture of Polyribosomes followed by RNA sequencing (ACAPseq) - for identifying PPIs. ACAPseq harnesses the power of massively parallel RNA sequencing (RNAseq) to quantify the enrichment of polyribosomes based on the affinity of their associated nascent polypeptides for an immobilized protein 'bait'. This method was developed and tested using neonatal mouse brain polyribosomes and a variety of extracellular domains as baits. Of 92 baits tested, 25 identified one or more binding partners that appear to be biologically relevant; additional candidate partners remain to be validated. ACAPseq can detect binding to targets that are present at less than 1 part in 100,000 in the starting polyribosome preparation. One of the observed PPIs was analyzed in detail, revealing the mode of homophilic binding for Protocadherin-9 (PCDH9), a non-clustered Protocadherin family member.

Transcriptional and epigenomic landscapes of CNS and non-CNS vascular endothelial cells.

Vascular endothelial cell (EC) function depends on appropriate organ-specific molecular and cellular specializations. To explore genomic mechanisms that control this specialization, we have analyzed and compared the transcriptome, accessible chromatin, and DNA methylome landscapes from mouse brain, liver, lung, and kidney ECs. Analysis of transcription factor (TF) gene expression and TF motifs at candidate cis-regulatory elements reveals both shared and organ-specific EC regulatory networks. In the embryo, only those ECs that are adjacent to or within the central nervous system (CNS) exhibit canonical Wnt signaling, which correlates precisely with blood-brain barrier (BBB) differentiation and Zic3 expression. In the early postnatal brain, single-cell RNA-seq of purified ECs reveals (1) close relationships between veins and mitotic cells and between arteries and tip cells, (2) a division of capillary ECs into vein-like and artery-like classes, and (3) new endothelial subtype markers, including new validated tip cell markers.

The Student Curriculum Review Team: How we catalyze curricular changes through a student-centered approach.

Student feedback is a valuable asset in curriculum evaluation and improvement, but many institutions have faced challenges implementing it in a meaningful way. In this article, we report the rationale, process and impact of the Student Curriculum Review Team (SCRT), a student-led and faculty-supported organization at the Johns Hopkins University School of Medicine. SCRT's evaluation of each pre-clinical course is composed of a comprehensive three-step process: a review of course evaluation data, a Town Hall Meeting and online survey to generate and assess potential solutions, and a thoughtful discussion with course directors. Over the past two years, SCRT has demonstrated the strength of its approach by playing a substantial role in improving medical education, as reported by students and faculty. Furthermore, SCRT's uniquely student-centered, collaborative model has strengthened relationships between students and faculty and is one that could be readily adapted to other medical schools or academic institutions.