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Schoch K, Esteves C, Bican A, Spillmann R, Cope H, McConkie-Rosell A, Walley N, Fernandez L, Kohler JN, Bonner D, Reuter C, Stong N, Mulvihill JJ, Novacic D, Wolfe L, Abdelbaki A, Toro C, Tifft C, Malicdan M, Gahl W, Liu P, Newman J, Goldstein DB, Hom J, Sampson J, Wheeler MT, Cogan J, Bernstein JA, Adams DR, McCray AT, Shashi V. Clinical sites of the Undiagnosed Diseases Network: unique contributions to genomic medicine and science. Genet Med 2021; 23:259-271. [PMID: 33093671 PMCID: PMC7867619 DOI: 10.1038/s41436-020-00984-z] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2020] [Revised: 09/17/2020] [Accepted: 09/18/2020] [Indexed: 11/08/2022] Open
Abstract
PURPOSE The NIH Undiagnosed Diseases Network (UDN) evaluates participants with disorders that have defied diagnosis, applying personalized clinical and genomic evaluations and innovative research. The clinical sites of the UDN are essential to advancing the UDN mission; this study assesses their contributions relative to standard clinical practices. METHODS We analyzed retrospective data from four UDN clinical sites, from July 2015 to September 2019, for diagnoses, new disease gene discoveries and the underlying investigative methods. RESULTS Of 791 evaluated individuals, 231 received 240 diagnoses and 17 new disease-gene associations were recognized. Straightforward diagnoses on UDN exome and genome sequencing occurred in 35% (84/240). We considered these tractable in standard clinical practice, although genome sequencing is not yet widely available clinically. The majority (156/240, 65%) required additional UDN-driven investigations, including 90 diagnoses that occurred after prior nondiagnostic exome sequencing and 45 diagnoses (19%) that were nongenetic. The UDN-driven investigations included complementary/supplementary phenotyping, innovative analyses of genomic variants, and collaborative science for functional assays and animal modeling. CONCLUSION Investigations driven by the clinical sites identified diagnostic and research paradigms that surpass standard diagnostic processes. The new diagnoses, disease gene discoveries, and delineation of novel disorders represent a model for genomic medicine and science.
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Schwalm S, Beyer S, Hafizi R, Trautmann S, Geisslinger G, Adams DR, Pyne S, Pyne N, Schaefer L, Huwiler A, Pfeilschifter J. Validation of highly selective sphingosine kinase 2 inhibitors SLM6031434 and HWG-35D as effective anti-fibrotic treatment options in a mouse model of tubulointerstitial fibrosis. Cell Signal 2020; 79:109881. [PMID: 33301900 DOI: 10.1016/j.cellsig.2020.109881] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2020] [Revised: 12/04/2020] [Accepted: 12/06/2020] [Indexed: 01/17/2023]
Abstract
Renal fibrosis is characterized by chronic inflammation and excessive accumulation of extracellular matrix and progressively leads to functional insufficiency and even total loss of kidney function. In this study we investigated the anti-fibrotic potential of two highly selective and potent SK2 inhibitors, SLM6031434 and HWG-35D, in unilateral ureter obstruction (UUO), a model for progressive renal fibrosis, in mice. In both cases, treatment with SLM6031434 or HWG-35D resulted in an attenuated fibrotic response to UUO in comparison to vehicle-treated mice as demonstrated by reduced collagen accumulation and a decreased expression of collagen-1 (Col1), fibronectin-1 (FN-1), connective tissue growth factor (CTGF), and α-smooth muscle actin (α-SMA). Similar to our previous study in Sphk2-/- mice, we found an increased protein expression of Smad7, a negative regulator of the pro-fibrotic TGFβ/Smad signalling cascade, accompanied by a strong accumulation of sphingosine in SK2 inhibitor-treated kidneys. Treatment of primary renal fibroblasts with SLM6031434 or HWG-35D dose-dependently increased Smad7 expression and ameliorated the expression of Col1, FN-1 and CTGF. In summary, these data prove the anti-fibrotic potential of SK2 inhibition in a mouse model of renal fibrosis, thereby validating SK2 as pharmacological target for the treatment of fibrosis in chronic kidney disease.
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Adams DR, Petukhova Y, Halpern LR. The versatile "lip switch" or transitional flap vestibuloplasty combined with alveoloplasty and implant placement to treat atrophic mandibles with inadequate vestibules and attached tissue: A case series and review of the literature. SPECIAL CARE IN DENTISTRY 2020; 41:78-84. [PMID: 33270928 DOI: 10.1111/scd.12546] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2020] [Revised: 11/11/2020] [Accepted: 11/13/2020] [Indexed: 11/30/2022]
Abstract
INTRODUCTION/AIMS The edentulous mandibular ridge and associated shallow vestibule are often seen as a challenge in the oral rehabilitation of patients. Dental implants can provide an improvement in mastication and patient satisfaction. The aim of this study is to utilize a preprosthetic mucosal flap combined with a repositional periosteal flap concomitant with an alveoloplasty and placement of endosteal implants as a single-stage procedure in the anterior mandible. This approach provides a valued alternative for dental rehabilitation in patients with poor masticatory efficiency using a conventional denture. METHODS Eight patients underwent the preprosthetic surgical plan in the oral surgery clinic of the dental school during a 1-year period. Age, sex, preoperative, and postoperative vestibular depth, as well as hard and soft tissue elements were measured (P < .05) at 4-6 months. RESULTS Mean age was 53 years ± 14.62 (N = 8). Anterior mandible height was 19 ± 4.8 mm. A significant difference was measured using a two-tailed Student's t-test between pre- and postoperative vestibular depths, respectively (3.9 mm vs 10.5 ± 0.96 mm; P < .01). CONCLUSIONS A lip switch vestibuloplasty combined with placement of two implants provide a one-stage procedure that is convenient, provides a shorter postoperative period, and can be financially affordable. Future research requires larger sampling to support this treatment as a standard of care.
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Meissner LE, Macnamara EF, D'Souza P, Yang J, Vezina G, Ferreira CR, Zein WM, Tifft CJ, Adams DR. DYRK1A pathogenic variants in two patients with syndromic intellectual disability and a review of the literature. Mol Genet Genomic Med 2020; 8:e1544. [PMID: 33159716 PMCID: PMC7767569 DOI: 10.1002/mgg3.1544] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2020] [Revised: 09/24/2020] [Accepted: 10/16/2020] [Indexed: 11/12/2022] Open
Abstract
BACKGROUND DYRK1A-Related Intellectual Disability Syndrome is a rare autosomal dominant condition characterized by intellectual disability, speech and language delays, microcephaly, facial dysmorphism, and feeding difficulties. Affected individuals represent simplex cases that result from de novo heterozygous pathogenic variants in DYRK1A (OMIM 614104), or chromosomal structural rearrangements involving the DYRK1A locus. Due to the rarity of DYRK1A-Related Intellectual Disability Syndrome, the spectrum of symptoms associated with this disease has not been completely defined. METHODS AND RESULTS We present two unrelated cases of DYRK1A-Related Intellectual Disability Syndrome resulting from variants in DYRK1A. Both probands presented to the National Institutes of Health (NIH) with multiple dysmorphic facial features, primary microcephaly, absent or minimal speech, feeding difficulties, and cognitive impairment; features that have been previously reported in individuals with DYRK1A. During NIH evaluation, additional features of enlarged cerebral subarachnoid spaces, retinal vascular tortuosity, and bilateral anomalous large optic discs with increased cup-to-disc ratio were identified in the first proband and multiple ophthalmologic abnormalities and sensorineural hearing loss were identified in the second proband. CONCLUSION We recommend that the workup of future of patients include a comprehensive eye exam. Early establishment of physical, occupational, and speech therapy may help in the management of ataxia, hypertonia, and speech impairments common in these patients.
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Shin SH, Kim HY, Yoon HS, Park WJ, Adams DR, Pyne NJ, Pyne S, Park JW. A Novel Selective Sphingosine Kinase 2 Inhibitor, HWG-35D, Ameliorates the Severity of Imiquimod-Induced Psoriasis Model by Blocking Th17 Differentiation of Naïve CD4 T Lymphocytes. Int J Mol Sci 2020; 21:ijms21218371. [PMID: 33171607 PMCID: PMC7664669 DOI: 10.3390/ijms21218371] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2020] [Revised: 11/03/2020] [Accepted: 11/05/2020] [Indexed: 02/07/2023] Open
Abstract
Sphingosine kinases (SK) catalyze the phosphorylation of sphingosine to generate sphingosine-1-phosphate. Two isoforms of SK (SK1 and SK2) exist in mammals. Previously, we showed the beneficial effects of SK2 inhibition, using ABC294640, in a psoriasis mouse model. However, ABC294640 also induces the degradation of SK1 and dihydroceramide desaturase 1 (DES1). Considering these additional effects of ABC294640, we re-examined the efficacy of SK2 inhibition in an IMQ-induced psoriasis mouse model using a novel SK2 inhibitor, HWG-35D, which exhibits nM potency and 100-fold selectivity for SK2 over SK1. Topical application of HWG-35D ameliorated IMQ-induced skin lesions and normalized the serum interleukin-17A levels elevated by IMQ. Application of HWG-35D also decreased skin mRNA levels of interleukin-17A, K6 and K16 genes induced by IMQ. Consistent with the previous data using ABC294640, HWG-35D also blocked T helper type 17 differentiation of naïve CD4+ T cells with concomitant reduction of SOCS1. Importantly, HWG-35D did not affect SK1 or DES1 expression levels. These results reaffirm an important role of SK2 in the T helper type 17 response and suggest that highly selective and potent SK2 inhibitors such as HWG-35D might be of therapeutic use for the treatment of psoriasis.
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Blanco-Sánchez B, Clément A, Stednitz SJ, Kyle J, Peirce JL, McFadden M, Wegner J, Phillips JB, Macnamara E, Huang Y, Adams DR, Toro C, Gahl WA, Malicdan MCV, Tifft CJ, Zink EM, Bloodsworth KJ, Stratton KG, Koeller DM, Metz TO, Washbourne P, Westerfield M. Correction: yippee like 3 (ypel3) is a novel gene required for myelinating and perineurial glia development. PLoS Genet 2020; 16:e1009156. [PMID: 33104717 PMCID: PMC7588083 DOI: 10.1371/journal.pgen.1009156] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
[This corrects the article DOI: 10.1371/journal.pgen.1008841.].
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Halpern LR, Adams DR. Medically Complex Dental Implant Patients: Controversies About Systemic Disease and Dental Implant Success/Survival. Dent Clin North Am 2020; 65:1-19. [PMID: 33213704 DOI: 10.1016/j.cden.2020.08.001] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Advances in dental implant therapy have created choices to enhance the expectations of dental practitioners and their patients with respect to oral rehabilitation at any age after childhood and regardless of, in most cases, medical disabilities. The medical status of the patient however can significantly influence the success rate of dental implant therapy. This article applies the hierarchy of scientific evidence ranging from case reports, retrospective, prospective cohort investigations, systematic reviews, and meta-analyses criteria in order to determine whether dental implant placement in medically compromised patients yields any detrimental sequelae.
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Adams DR, Pyne S, Pyne NJ. Structure-function analysis of lipid substrates and inhibitors of sphingosine kinases. Cell Signal 2020; 76:109806. [PMID: 33035646 DOI: 10.1016/j.cellsig.2020.109806] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2020] [Accepted: 10/05/2020] [Indexed: 12/21/2022]
Abstract
The sphingosine kinases, SK1 and SK2, catalyse the formation of the bioactive signalling lipid, sphingosine 1-phosphate (S1P), from sphingosine. SK1 and SK2 differ in their subcellular localisation, trafficking and regulation, but the isoforms are also distinct in their selectivity toward naturally occurring and synthetic ligands as substrates and inhibitors. To date, only the structure of SK1 has been determined, and a structural basis for selectivity differences in substrate handling by SK2 has yet to be established. Here we present a structural rationale, based on homology modelling and ligand docking, to account for the capacity of SK2, but not SK1, to efficiently process the pharmacologically active substances, fingolimod (FTY720) and safingol, as substrates. We propose that two key residue differences in hSK2 (Ser305/Thr584 in place of Ala175/Ala339 in hSK1) facilitate conformational switching in the lipid head group anchor residue, Asp308 (corresponding to Asp178 in hSK1), to accommodate substrate diversity for SK2. Our analysis accounts for the contrasting behaviour of fingolimod and safingol as non-turnover inhibitors of SK1, but substrates for SK2, and the observed stereoselectivity for phosphorylation of the pro-S hydroxymethyl group of fingolimod to generate (S)-FTY720-P in vivo. We also rationalise why methylation of the pro-R hydroxymethyl of FTY720 switches the behaviour of the resulting compound, (R)-FTY720 methyl ether (ROMe), to SK2-selective inhibition. Whilst the pharmacological significance of (S)-FTY720-P is firmly established, as the active principle of fingolimod in treating relapsing-remitting multiple sclerosis, the potential importance of SK-mediated phosphorylation of other substrates, such as safingol and non-canonical naturally occuring substrates such as (4E,nZ)-sphingadienes, is less widely appreciated. Thus, the contribution of SK2-derived safingol 1-phosphate to the anti-cancer activity of safingol should be considered. Similarly, the biological role of sphingadiene 1-phosphates derived from plant-based dietary sphingadienes, which we also show here are substrates for both SK1 and SK2, merits investigation.
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Halpern LR, Adams DR. The Dentoalveolar Surgical Patient: Perioperative Principles Based on Contemporary Controversies. Oral Maxillofac Surg Clin North Am 2020; 32:495-510. [PMID: 32912778 DOI: 10.1016/j.coms.2020.07.004] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Dentoalveolar surgery comprises more than 50% of the practice of oral and maxillofacial surgeons worldwide and is the most commonly performed category of surgical procedure. Optimal strategies for management of many medical problems, however, remain unclear. Remaining current on medical and surgical perioperative strategies is a standard for best practice. This article provides contemporary approaches for the perioperative management of patients presenting for dentoalveolar surgery. Attention will be directed to the perioperative management of cardiovascular disease, diabetes, and obesity. These diseases are chosen owing to controversies with respect to good scientific evidence that supports a standard of perioperative care.
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Tambe MA, Ng BG, Shimada S, Wolfe LA, Adams DR, Gahl WA, Bamshad MJ, Nickerson DA, Malicdan MC, Freeze HH. Mutations in GET4 disrupt the transmembrane domain recognition complex pathway. J Inherit Metab Dis 2020; 43:1037-1045. [PMID: 32395830 PMCID: PMC7508799 DOI: 10.1002/jimd.12249] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/28/2020] [Revised: 04/21/2020] [Accepted: 05/07/2020] [Indexed: 01/06/2023]
Abstract
The transmembrane domain recognition complex (TRC) targets cytoplasmic C-terminal tail-anchored (TA) proteins to their respective membranes in the endoplasmic reticulum (ER), Golgi, and mitochondria. It is composed of three proteins, GET4, BAG6, and GET5. We identified an individual with compound heterozygous missense variants (p.Arg122His, p.Ile279Met) in GET4 that reduced all three TRC proteins by 70% to 90% in his fibroblasts, suggesting a possible defect in TA protein targeting. He presented with global developmental delay, intellectual disabilities, seizures, facial dysmorphism, and delayed bone age. We found the TA protein, syntaxin 5, is poorly targeted to Golgi membranes compared to normal controls. Since GET4 regulates ER to Golgi transport, we hypothesized that such transport would be disrupted in his fibroblasts, and discovered that retrograde (but not anterograde) transport was significantly reduced. Despite reduction in the three TRC proteins, their mRNA levels were unchanged, suggesting increased degradation in patient fibroblasts. Treating fibroblasts with the FDA-approved proteasome inhibitor, bortezomib (10 nM), restored syntaxin 5 localization and nearly normalized the levels of all three TRC proteins. Our study identifies the first individual with GET4 mutations.
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Hartley T, Lemire G, Kernohan KD, Howley HE, Adams DR, Boycott KM. New Diagnostic Approaches for Undiagnosed Rare Genetic Diseases. Annu Rev Genomics Hum Genet 2020; 21:351-372. [DOI: 10.1146/annurev-genom-083118-015345] [Citation(s) in RCA: 30] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Accurate diagnosis is the cornerstone of medicine; it is essential for informed care and promoting patient and family well-being. However, families with a rare genetic disease (RGD) often spend more than five years on a diagnostic odyssey of specialist visits and invasive testing that is lengthy, costly, and often futile, as 50% of patients do not receive a molecular diagnosis. The current diagnostic paradigm is not well designed for RGDs, especially for patients who remain undiagnosed after the initial set of investigations, and thus requires an expansion of approaches in the clinic. Leveraging opportunities to participate in research programs that utilize new technologies to understand RGDs is an important path forward for patients seeking a diagnosis. Given recent advancements in such technologies and international initiatives, the prospect of identifying a molecular diagnosis for all patients with RGDs has never been so attainable, but achieving this goal will require global cooperation at an unprecedented scale.
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Adams DR, Gifford ME. Functional and Environmental Constraints on Prey Capture Speed in a Lizard. Integr Org Biol 2020; 2:obaa022. [PMID: 33791563 PMCID: PMC7715460 DOI: 10.1093/iob/obaa022] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Movement is an important component of animal behavior and determines how an organism interacts with its environment. The speed at which an animal moves through its environment can be constrained by internal (e.g., physiological state) and external factors (e.g., habitat complexity). When foraging, animals should move at speeds that maximize prey capture while minimizing mistakes (i.e., missing prey, slipping). We used experimental arenas containing obstacles spaced in different arrays to test how variation in habitat complexity influenced attack distance, prey capture speed, and foraging success in the Prairie Lizard. Obstacles spaced uniformly across arenas resulted in 15% slower prey capture speed and 30–38% shorter attack distance compared to arenas with no obstacles or with obstacles clustered in opposite corners of the arena. Prey capture probability was not influenced by arena type or capture speed, but declined with increasing attack distance. Similarly, the probability of prey consumption declined with attack distance across arena types. However, prey consumption probability declined with increasing prey capture speed in more open arenas but not in the cluttered arena. Foraging accuracy declined with increasing speed in more open arenas, and remained relatively constant when obstacles were in closer proximity. Foraging success was primarily constrained by intrinsic properties (speed-maneuverability tradeoff) when ample space was available, but environmental conditions had a greater impact on foraging success in “cluttered” habitats. This empirical test of theoretical predictions about optimal movement speeds in animals provides a step forward in understanding how animals select speeds in nature.
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Blanco-Sánchez B, Clément A, Stednitz SJ, Kyle J, Peirce JL, McFadden M, Wegner J, Phillips JB, Macnamara E, Huang Y, Adams DR, Toro C, Gahl WA, Malicdan MCV, Tifft CJ, Zink EM, Bloodsworth KJ, Stratton KG, Koeller DM, Metz TO, Washbourne P, Westerfield M. yippee like 3 (ypel3) is a novel gene required for myelinating and perineurial glia development. PLoS Genet 2020; 16:e1008841. [PMID: 32544203 PMCID: PMC7319359 DOI: 10.1371/journal.pgen.1008841] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2019] [Revised: 06/26/2020] [Accepted: 05/08/2020] [Indexed: 12/30/2022] Open
Abstract
Hypomyelination, a neurological condition characterized by decreased production of myelin sheets by glial cells, often has no known etiology. Elucidating the genetic causes of hypomyelination provides a better understanding of myelination, as well as means to diagnose, council, and treat patients. Here, we present evidence that YIPPEE LIKE 3 (YPEL3), a gene whose developmental role was previously unknown, is required for central and peripheral glial cell development. We identified a child with a constellation of clinical features including cerebral hypomyelination, abnormal peripheral nerve conduction, hypotonia, areflexia, and hypertrophic peripheral nerves. Exome and genome sequencing revealed a de novo mutation that creates a frameshift in the open reading frame of YPEL3, leading to an early stop codon. We used zebrafish as a model system to validate that YPEL3 mutations are causative of neuropathy. We found that ypel3 is expressed in the zebrafish central and peripheral nervous system. Using CRISPR/Cas9 technology, we created zebrafish mutants carrying a genomic lesion similar to that of the patient. Our analysis revealed that Ypel3 is required for development of oligodendrocyte precursor cells, timely exit of the perineurial glial precursors from the central nervous system (CNS), formation of the perineurium, and Schwann cell maturation. Consistent with these observations, zebrafish ypel3 mutants have metabolomic signatures characteristic of oligodendrocyte and Schwann cell differentiation defects, show decreased levels of Myelin basic protein in the central and peripheral nervous system, and develop defasciculated peripheral nerves. Locomotion defects were observed in adult zebrafish ypel3 mutants. These studies demonstrate that Ypel3 is a novel gene required for perineurial cell development and glial myelination.
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Ates KM, Wang T, Moreland T, Veeranan-Karmegam R, Ma M, Jeter C, Anand P, Wenzel W, Kim HG, Wolfe LA, Stephen J, Adams DR, Markello T, Tifft CJ, Settlage R, Gahl WA, Gonsalvez GB, Malicdan MC, Flanagan-Steet H, Pan YA. Deficiency in the endocytic adaptor proteins PHETA1/2 impairs renal and craniofacial development. Dis Model Mech 2020; 13:dmm041913. [PMID: 32152089 PMCID: PMC7272357 DOI: 10.1242/dmm.041913] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2019] [Accepted: 02/27/2020] [Indexed: 12/20/2022] Open
Abstract
A critical barrier in the treatment of endosomal and lysosomal diseases is the lack of understanding of the in vivo functions of the putative causative genes. We addressed this by investigating a key pair of endocytic adaptor proteins, PH domain-containing endocytic trafficking adaptor 1 and 2 (PHETA1/2; also known as FAM109A/B, Ses1/2, IPIP27A/B), which interact with the protein product of OCRL, the causative gene for Lowe syndrome. Here, we conducted the first study of PHETA1/2 in vivo, utilizing the zebrafish system. We found that impairment of both zebrafish orthologs, pheta1 and pheta2, disrupted endocytosis and ciliogenesis in renal tissues. In addition, pheta1/2 mutant animals exhibited reduced jaw size and delayed chondrocyte differentiation, indicating a role in craniofacial development. Deficiency of pheta1/2 resulted in dysregulation of cathepsin K, which led to an increased abundance of type II collagen in craniofacial cartilages, a marker of immature cartilage extracellular matrix. Cathepsin K inhibition rescued the craniofacial phenotypes in the pheta1/2 double mutants. The abnormal renal and craniofacial phenotypes in the pheta1/2 mutant animals were consistent with the clinical presentation of a patient with a de novo arginine (R) to cysteine (C) variant (R6C) of PHETA1. Expressing the patient-specific variant in zebrafish exacerbated craniofacial deficits, suggesting that the R6C allele acts in a dominant-negative manner. Together, these results provide insights into the in vivo roles of PHETA1/2 and suggest that the R6C variant is contributory to the pathogenesis of disease in the patient.This article has an associated First Person interview with the first author of the paper.
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Davids M, Menezes M, Guo Y, McLean SD, Hakonarson H, Collins F, Worgan L, Billington CJ, Maric I, Littlejohn RO, Onyekweli T, Adams DR, Tifft CJ, Gahl WA, Wolfe LA, Christodoulou J, Malicdan MCV. Homozygous splice-variants in human ARV1 cause GPI-anchor synthesis deficiency. Mol Genet Metab 2020; 130:49-57. [PMID: 32165008 PMCID: PMC7303973 DOI: 10.1016/j.ymgme.2020.02.005] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/21/2019] [Revised: 01/15/2020] [Accepted: 02/07/2020] [Indexed: 10/25/2022]
Abstract
BACKGROUND Mutations in the ARV1 Homolog, Fatty Acid Homeostasis Modulator (ARV1), have recently been described in association with early infantile epileptic encephalopathy 38. Affected individuals presented with epilepsy, ataxia, profound intellectual disability, visual impairment, and central hypotonia. In S. cerevisiae, Arv1 is thought to be involved in sphingolipid metabolism and glycophosphatidylinositol (GPI)-anchor synthesis. The function of ARV1 in human cells, however, has not been elucidated. METHODS Mutations were discovered through whole exome sequencing and alternate splicing was validated on the cDNA level. Expression of the variants was determined by qPCR and Western blot. Expression of GPI-anchored proteins on neutrophils and fibroblasts was analyzed by FACS and immunofluorescence microscopy, respectively. RESULTS Here we describe seven patients from two unrelated families with biallelic splice mutations in ARV1. The patients presented with early onset epilepsy, global developmental delays, profound hypotonia, delayed speech development, cortical visual impairment, and severe generalized cerebral and cerebellar atrophy. The splice variants resulted in decreased ARV1 expression and significant decreases in GPI-anchored protein on the membranes of neutrophils and fibroblasts, indicating that the loss of ARV1 results in impaired GPI-anchor synthesis. CONCLUSION Loss of GPI-anchored proteins on our patients' cells confirms that the yeast Arv1 function of GPI-anchor synthesis is conserved in humans. Overlap between the phenotypes in our patients and those reported for other GPI-anchor disorders suggests that ARV1-deficiency is a GPI-anchor synthesis disorder.
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Baynam GS, Groft S, van der Westhuizen FH, Gassman SD, du Plessis K, Coles EP, Selebatso E, Selebatso M, Gaobinelwe B, Selebatso T, Joel D, Llera VA, Vorster BC, Wuebbels B, Djoudalbaye B, Austin CP, Kumuthini J, Forman J, Kaufmann P, Chipeta J, Gavhed D, Larsson A, Stojiljkovic M, Nordgren A, Roldan EJA, Taruscio D, Wong-Rieger D, Nowak K, Bilkey GA, Easteal S, Bowdin S, Reichardt JKV, Beltran S, Kosaki K, van Karnebeek CDM, Gong M, Shuyang Z, Mehrian-Shai R, Adams DR, Puri RD, Zhang F, Pachter N, Muenke M, Nellaker C, Gahl WA, Cederroth H, Broley S, Schoonen M, Boycott KM, Posada M. A call for global action for rare diseases in Africa. Nat Genet 2020; 52:21-26. [PMID: 31873296 DOI: 10.1038/s41588-019-0552-2] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
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Mao D, Reuter CM, Ruzhnikov MR, Beck AE, Farrow EG, Emrick LT, Rosenfeld JA, Mackenzie KM, Robak L, Wheeler MT, Burrage LC, Jain M, Liu P, Calame D, Küry S, Sillesen M, Schmitz-Abe K, Tonduti D, Spaccini L, Iascone M, Genetti CA, Koenig MK, Graf M, Tran A, Alejandro M, Lee BH, Thiffault I, Agrawal PB, Bernstein JA, Bellen HJ, Chao HT, Acosta MT, Adam M, Adams DR, Agrawal PB, Alejandro ME, Allard P, Alvey J, Amendola L, Andrews A, Ashley EA, Azamian MS, Bacino CA, Bademci G, Baker E, Balasubramanyam A, Baldridge D, Bale J, Bamshad M, Barbouth D, Batzli GF, Bayrak-Toydemir P, Beck A, Beggs AH, Bejerano G, Bellen HJ, Bennet J, Berg-Rood B, Bernier R, Bernstein JA, Berry GT, Bican A, Bivona S, Blue E, Bohnsack J, Bonnenmann C, Bonner D, Botto L, Briere LC, Brokamp E, Burke EA, Burrage LC, Butte MJ, Byers P, Carey J, Carrasquillo O, Chang TCP, Chanprasert S, Chao HT, Clark GD, Coakley TR, Cobban LA, Cogan JD, Cole FS, Colley HA, Cooper CM, Cope H, Craigen WJ, Cunningham M, D’Souza P, Dai H, Dasari S, Davids M, Dayal JG, Dell’Angelica EC, Dhar SU, Dipple K, Doherty D, Dorrani N, Douine ED, Draper DD, Duncan L, Earl D, Eckstein DJ, Emrick LT, Eng CM, Esteves C, Estwick T, Fernandez L, Ferreira C, Fieg EL, Fisher PG, Fogel BL, Forghani I, Fresard L, Gahl WA, Glass I, Godfrey RA, Golden-Grant K, Goldman AM, Goldstein DB, Grajewski A, Groden CA, Gropman AL, Hahn S, Hamid R, Hanchard NA, Hayes N, High F, Hing A, Hisama FM, Holm IA, Hom J, Horike-Pyne M, Huang A, Huang Y, Isasi R, Jamal F, Jarvik GP, Jarvik J, Jayadev S, Jiang YH, Johnston JM, Karaviti L, Kelley EG, Kiley D, Kohane IS, Kohler JN, Krakow D, Krasnewich DM, Korrick S, Koziura M, Krier JB, Lalani SR, Lam B, Lam C, Lanpher BC, Lanza IR, Lau CC, LeBlanc K, Lee BH, Lee H, Levitt R, Lewis RA, Lincoln SA, Liu P, Liu XZ, Longo N, Loo SK, Loscalzo J, Maas RL, Macnamara EF, MacRae CA, Maduro VV, Majcherska MM, Malicdan MCV, Mamounas LA, Manolio TA, Mao R, Maravilla K, Markello TC, Marom R, Marth G, Martin BA, Martin MG, Martínez-Agosto JA, Marwaha S, McCauley J, McConkie-Rosell A, McCormack CE, McCray AT, Mefford H, Merritt JL, Might M, Mirzaa G, Morava-Kozicz E, Moretti PM, Morimoto M, Mulvihill JJ, Murdock DR, Nath A, Nelson SF, Newman JH, Nicholas SK, Nickerson D, Novacic D, Oglesbee D, Orengo JP, Pace L, Pak S, Pallais JC, Palmer CG, Papp JC, Parker NH, Phillips JA, Posey JE, Postlethwait JH, Potocki L, Pusey BN, Quinlan A, Raskind W, Raja AN, Renteria G, Reuter CM, Rives L, Robertson AK, Rodan LH, Rosenfeld JA, Rowley RK, Ruzhnikov M, Sacco R, Sampson JB, Samson SL, Saporta M, Scott CR, Schaechter J, Schedl T, Schoch K, Scott DA, Shakachite L, Sharma P, Shashi V, Shin J, Signer R, Sillari CH, Silverman EK, Sinsheimer JS, Sisco K, Smith KS, Solnica-Krezel L, Spillmann RC, Stoler JM, Stong N, Sullivan JA, Sun A, Sutton S, Sweetser DA, Sybert V, Tabor HK, Tamburro CP, Tan QKG, Tekin M, Telischi F, Thorson W, Tifft CJ, Toro C, Tran AA, Urv TK, Velinder M, Viskochil D, Vogel TP, Wahl CE, Wallace S, Walley NM, Walsh CA, Walker M, Wambach J, Wan J, Wang LK, Wangler MF, Ward PA, Wegner D, Wener M, Westerfield M, Wheeler MT, Wise AL, Wolfe LA, Woods JD, Yamamoto S, Yang J, Yoon AJ, Yu G, Zastrow DB, Zhao C, Zuchner S. De novo EIF2AK1 and EIF2AK2 Variants Are Associated with Developmental Delay, Leukoencephalopathy, and Neurologic Decompensation. Am J Hum Genet 2020; 106:570-583. [PMID: 32197074 PMCID: PMC7118694 DOI: 10.1016/j.ajhg.2020.02.016] [Citation(s) in RCA: 37] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2019] [Accepted: 02/28/2020] [Indexed: 02/03/2023] Open
Abstract
EIF2AK1 and EIF2AK2 encode members of the eukaryotic translation initiation factor 2 alpha kinase (EIF2AK) family that inhibits protein synthesis in response to physiologic stress conditions. EIF2AK2 is also involved in innate immune response and the regulation of signal transduction, apoptosis, cell proliferation, and differentiation. Despite these findings, human disorders associated with deleterious variants in EIF2AK1 and EIF2AK2 have not been reported. Here, we describe the identification of nine unrelated individuals with heterozygous de novo missense variants in EIF2AK1 (1/9) or EIF2AK2 (8/9). Features seen in these nine individuals include white matter alterations (9/9), developmental delay (9/9), impaired language (9/9), cognitive impairment (8/9), ataxia (6/9), dysarthria in probands with verbal ability (6/9), hypotonia (7/9), hypertonia (6/9), and involuntary movements (3/9). Individuals with EIF2AK2 variants also exhibit neurological regression in the setting of febrile illness or infection. We use mammalian cell lines and proband-derived fibroblasts to further confirm the pathogenicity of variants in these genes and found reduced kinase activity. EIF2AKs phosphorylate eukaryotic translation initiation factor 2 subunit 1 (EIF2S1, also known as EIF2α), which then inhibits EIF2B activity. Deleterious variants in genes encoding EIF2B proteins cause childhood ataxia with central nervous system hypomyelination/vanishing white matter (CACH/VWM), a leukodystrophy characterized by neurologic regression in the setting of febrile illness and other stressors. Our findings indicate that EIF2AK2 missense variants cause a neurodevelopmental syndrome that may share phenotypic and pathogenic mechanisms with CACH/VWM.
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Halpern LR, Adams DR, Clarkson E. Treatment of the Dental Patient with Bleeding Dyscrasias: Etiologies and Management Options for Surgical Success in Practice. Dent Clin North Am 2020; 64:411-434. [PMID: 32111278 DOI: 10.1016/j.cden.2019.12.010] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
The oral health care provider sees a significant number of patients in his or her practice who suffer from systemic diseases affecting the ability to clot. These medical issues can be acquired or inherited bleeding dyscrasias requiring pharmacologic therapy during the perioperative period. Patients with inherited or acquired bleeding disorders require careful attention with respect to the assessment of bleeding risk. This article develops algorithms to manage acquired and inherited bleeding dyscrasias. These approaches include a discussion of the epidemiology of bleeding disorders in surgical patients, mechanism of hemostasis, and strategies for patient management based on the etiology of bleeding disorder.
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Abstract
There is substantial evidence that the enzymes, sphingosine kinase 1 and 2, which catalyse the formation of the bioactive lipid sphingosine 1-phosphate, are involved in pathophysiological processes. In this chapter, we appraise the evidence that both enzymes are druggable and describe how isoform-specific inhibitors can be developed based on the plasticity of the sphingosine-binding site. This is contextualised with the effect of sphingosine kinase inhibitors in cancer, pulmonary hypertension, neurodegeneration, inflammation and sickling.
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Adams DR, Tollinche LE, Yeoh CB, Artman J, Mehta M, Phillips D, Fischer GW, Quinlan JJ, Sakai T. Short-term safety and effectiveness of sugammadex for surgical patients with end-stage renal disease: a two-centre retrospective study. Anaesthesia 2019; 75:348-352. [PMID: 31721151 DOI: 10.1111/anae.14914] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/15/2019] [Indexed: 12/17/2022]
Abstract
Sugammadex is a novel reversal agent for aminosteroid neuromuscular blocking drugs, especially rocuronium. Given its renal excretion, sugammadex is not recommended for patients with end-stage renal disease; however, reports exist of its use in this group of patients. This two-institutional retrospective observational study aimed to review the safety profile and effectiveness of sugammadex in surgical patients with end-stage renal disease who required pre-operative renal replacement therapy. Adult surgical patients with end-stage renal disease requiring pre-operative renal replacement therapy, who received sugammadex between April 2016 and January 2019, were studied. The primary outcome was the incidence of postoperative tracheal re-intubation within 48 h. The secondary outcome was the incidence of deferred tracheal extubation in the operating theatre. One hundred and fifty-eight patients were identified from 125,653 surgical patients: 48 patients (30%) underwent renal transplantation and 110 (70%) underwent non-renal transplantation procedures. There were 22 instances (14%) of deferred tracheal extubation due to surgical and/or pre-existing medical conditions. Out of the 136 patients who had the tracheal tube removed at the end of the procedure, three patients had their trachea re-intubated within 48 h: two patients developed pulmonary oedema resulting from volume overload; and one patient had worsening sepsis. No incidence of recurrence of neuromuscular blockade was observed. Of note, 24 (18%) patients were found to have incomplete neuromuscular blockade reversal with neostigmine but administration of sugammadex led to successful tracheal extubation. In conclusion, sugammadex appears to be safe and effective in adult patients with end-stage renal disease receiving pre-operative renal replacement therapy.
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Kanca O, Andrews JC, Lee PT, Patel C, Braddock SR, Slavotinek AM, Cohen JS, Gubbels CS, Aldinger KA, Williams J, Indaram M, Fatemi A, Yu TW, Agrawal PB, Vezina G, Simons C, Crawford J, Lau CC, Chung WK, Markello TC, Dobyns WB, Adams DR, Gahl WA, Wangler MF, Yamamoto S, Bellen HJ, Malicdan MCV. De Novo Variants in WDR37 Are Associated with Epilepsy, Colobomas, Dysmorphism, Developmental Delay, Intellectual Disability, and Cerebellar Hypoplasia. Am J Hum Genet 2019; 105:413-424. [PMID: 31327508 PMCID: PMC6699142 DOI: 10.1016/j.ajhg.2019.06.014] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2018] [Accepted: 06/14/2019] [Indexed: 12/16/2022] Open
Abstract
WD40 repeat-containing proteins form a large family of proteins present in all eukaryotes. Here, we identified five pediatric probands with de novo variants in WDR37, which encodes a member of the WD40 repeat protein family. Two probands shared one variant and the others have variants in nearby amino acids outside the WD40 repeats. The probands exhibited shared phenotypes of epilepsy, colobomas, facial dysmorphology reminiscent of CHARGE syndrome, developmental delay and intellectual disability, and cerebellar hypoplasia. The WDR37 protein is highly conserved in vertebrate and invertebrate model organisms and is currently not associated with a human disease. We generated a null allele of the single Drosophila ortholog to gain functional insights and replaced the coding region of the fly gene CG12333/wdr37 with GAL4. These flies are homozygous viable but display severe bang sensitivity, a phenotype associated with seizures in flies. Additionally, the mutant flies fall when climbing the walls of the vials, suggesting a defect in grip strength, and repeat the cycle of climbing and falling. Similar to wall clinging defect, mutant males often lose grip of the female abdomen during copulation. These phenotypes are rescued by using the GAL4 in the CG12333/wdr37 locus to drive the UAS-human reference WDR37 cDNA. The two variants found in three human subjects failed to rescue these phenotypes, suggesting that these alleles severely affect the function of this protein. Taken together, our data suggest that variants in WDR37 underlie a novel syndromic neurological disorder.
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Nelson AM, Cong Z, Gettle SL, Longenecker AL, Kidacki M, Kirby JS, Adams DR, Stairs DB, Danby FW. E‐cadherin and p120ctn protein expression are lost in hidradenitis suppurativa lesions. Exp Dermatol 2019; 28:867-871. [DOI: 10.1111/exd.13973] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2019] [Revised: 04/24/2019] [Accepted: 05/14/2019] [Indexed: 02/02/2023]
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Nicoli ER, Weston MR, Hackbarth M, Becerril A, Larson A, Zein WM, Baker PR, Burke JD, Dorward H, Davids M, Huang Y, Adams DR, Zerfas PM, Chen D, Markello TC, Toro C, Wood T, Elliott G, Vu M, Zheng W, Garrett LJ, Tifft CJ, Gahl WA, Day-Salvatore DL, Mindell JA, Malicdan MCV. Lysosomal Storage and Albinism Due to Effects of a De Novo CLCN7 Variant on Lysosomal Acidification. Am J Hum Genet 2019; 104:1127-1138. [PMID: 31155284 PMCID: PMC6562152 DOI: 10.1016/j.ajhg.2019.04.008] [Citation(s) in RCA: 47] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2019] [Accepted: 04/10/2019] [Indexed: 12/15/2022] Open
Abstract
Optimal lysosome function requires maintenance of an acidic pH maintained by proton pumps in combination with a counterion transporter such as the Cl-/H+ exchanger, CLCN7 (ClC-7), encoded by CLCN7. The role of ClC-7 in maintaining lysosomal pH has been controversial. In this paper, we performed clinical and genetic evaluations of two children of different ethnicities. Both children had delayed myelination and development, organomegaly, and hypopigmentation, but neither had osteopetrosis. Whole-exome and -genome sequencing revealed a de novo c.2144A>G variant in CLCN7 in both affected children. This p.Tyr715Cys variant, located in the C-terminal domain of ClC-7, resulted in increased outward currents when it was heterologously expressed in Xenopus oocytes. Fibroblasts from probands displayed a lysosomal pH approximately 0.2 units lower than that of control cells, and treatment with chloroquine normalized the pH. Primary fibroblasts from both probands also exhibited markedly enlarged intracellular vacuoles; this finding was recapitulated by the overexpression of human p.Tyr715Cys CLCN7 in control fibroblasts, reflecting the dominant, gain-of-function nature of the variant. A mouse harboring the knock-in Clcn7 variant exhibited hypopigmentation, hepatomegaly resulting from abnormal storage, and enlarged vacuoles in cultured fibroblasts. Our results show that p.Tyr715Cys is a gain-of-function CLCN7 variant associated with developmental delay, organomegaly, and hypopigmentation resulting from lysosomal hyperacidity, abnormal storage, and enlarged intracellular vacuoles. Our data supports the hypothesis that the ClC-7 antiporter plays a critical role in maintaining lysosomal pH.
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Arbabi A, Adams DR, Fidler S, Brudno M. Identifying Clinical Terms in Medical Text Using Ontology-Guided Machine Learning. JMIR Med Inform 2019; 7:e12596. [PMID: 31094361 PMCID: PMC6533869 DOI: 10.2196/12596] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2018] [Revised: 02/20/2019] [Accepted: 03/29/2019] [Indexed: 01/22/2023] Open
Abstract
Background Automatic recognition of medical concepts in unstructured text is an important component of many clinical and research applications, and its accuracy has a large impact on electronic health record analysis. The mining of medical concepts is complicated by the broad use of synonyms and nonstandard terms in medical documents. Objective We present a machine learning model for concept recognition in large unstructured text, which optimizes the use of ontological structures and can identify previously unobserved synonyms for concepts in the ontology. Methods We present a neural dictionary model that can be used to predict if a phrase is synonymous to a concept in a reference ontology. Our model, called the Neural Concept Recognizer (NCR), uses a convolutional neural network to encode input phrases and then rank medical concepts based on the similarity in that space. It uses the hierarchical structure provided by the biomedical ontology as an implicit prior embedding to better learn embedding of various terms. We trained our model on two biomedical ontologies—the Human Phenotype Ontology (HPO) and Systematized Nomenclature of Medicine - Clinical Terms (SNOMED-CT). Results We tested our model trained on HPO by using two different data sets: 288 annotated PubMed abstracts and 39 clinical reports. We achieved 1.7%-3% higher F1-scores than those for our strongest manually engineered rule-based baselines (P=.003). We also tested our model trained on the SNOMED-CT by using 2000 Intensive Care Unit discharge summaries from MIMIC (Multiparameter Intelligent Monitoring in Intensive Care) and achieved 0.9%-1.3% higher F1-scores than those of our baseline. The results of our experiments show high accuracy of our model as well as the value of using the taxonomy structure of the ontology in concept recognition. Conclusion Most popular medical concept recognizers rely on rule-based models, which cannot generalize well to unseen synonyms. In addition, most machine learning methods typically require large corpora of annotated text that cover all classes of concepts, which can be extremely difficult to obtain for biomedical ontologies. Without relying on large-scale labeled training data or requiring any custom training, our model can be efficiently generalized to new synonyms and performs as well or better than state-of-the-art methods custom built for specific ontologies.
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Onojafe IF, Megan LH, Melch MG, Aderemi JO, Alur RP, Abu-Asab MS, Chan CC, Bernardini IM, Albert JS, Cogliati T, Adams DR, Brooks BP. Minimal Efficacy of Nitisinone Treatment in a Novel Mouse Model of Oculocutaneous Albinism, Type 3. Invest Ophthalmol Vis Sci 2019; 59:4945-4952. [PMID: 30347088 PMCID: PMC6181301 DOI: 10.1167/iovs.16-20293] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Purpose Oral nitisinone has been shown to increase fur and ocular pigmentation in a mouse model of oculocutaneous albinism (OCA) due to hypomorphic mutations in tyrosinase (TYR), OCA1B. This study determines if nitisinone can improve ocular and/or fur pigmentation in a mouse model of OCA type 3 (OCA3), caused by mutation of the tyrosinase-related protein 1 (Tyrp1) gene. Methods Mice homozygous for a null allele in the Tyrp1 gene (C57BL/6J-Tyrp1 b-J/J) were treated with 8 mg/kg nitisinone or vehicle every other day by oral gavage. Changes in fur and ocular melanin pigmentation were monitored. Mature ocular melanosome number and size were quantified in pigmented ocular structures by electron microscopy. Results C57BL/6J-Tyrp1 b-J/J mice carry a novel c.403T>A; 404delG mutation in Tyrp1, predicted to result in premature truncation of the TYRP1 protein. Nitisinone treatment resulted in an approximately 7-fold increase in plasma tyrosine concentrations without overt toxicity. After 1 month of treatment, no change in the color of fur or pigmented ocular structures was observed. The distribution of melanosome cross-sectional area was unchanged in ocular tissues. There was no significant difference in the number of pigmented melanosomes in the RPE/choroid of nitisinone-treated and control groups. However, there was a significant difference in the number of pigmented melanosomes in the iris. Conclusions Treatment of a mouse model of OCA3 with oral nitisinone did not have a favorable clinical effect on melanin production and minimally affected the number of pigmented melanosomes in the iris stroma. As such, treatment of OCA3 patients with nitisinone is unlikely to be therapeutic.
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