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Taruscio D, Baynam G, Cederroth H, Groft SC, Klee EW, Kosaki K, Lasko P, Melegh B, Riess O, Salvatore M, Gahl WA. The Undiagnosed Diseases Network International: Five years and more! Mol Genet Metab 2020; 129:243-254. [PMID: 32033911 DOI: 10.1016/j.ymgme.2020.01.004] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/06/2019] [Revised: 01/08/2020] [Accepted: 01/08/2020] [Indexed: 11/23/2022]
Abstract
Undiagnosed rare diseases (URDs) account for a significant portion of the overall rare disease burden, depending upon the country. Hence, URDs represent an unmet medical need. A specific challenge posed by the ensemble of the URD patient cohort is the heterogeneity of its composition; the group, indeed, includes very rare, still unidentified conditions as well as clinical variants of recognized rare diseases. Exact disease recognition requires new approaches that cut across national and institutional boundaries, may need the implementation of methods new to diagnostics, and embrace clinical care and research. To address these issues, the Undiagnosed Diseases Network International (UDNI) was established in 2014, with the major aims of providing diagnoses to patients, implementing additional diagnostic tools, and fostering research on novel diseases, their mechanisms, and their pathways. The UDNI involves centres with internationally recognized expertise, and its scientific resources and know-how aim to fill the knowledge gaps that impede diagnosis, in particularly for ultra-rare diseases. Consequently, the UDNI fosters the translation of research into medical practice, aided by active patient involvement. The goals of the UDNI are to work collaboratively and at an international scale to: 1) provide diagnoses for individuals who have conditions that have eluded diagnosis by clinical experts; 2) gain insights into the etiology and pathogenesis of novel diseases; 3) contribute to standards of diagnosing unsolved patients; and 4) share the results of UDNI research in a timely manner and as broadly as possible.
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Boyd LC, O'Brien KJ, Ozkaya N, Lehky T, Meoded A, Gochuico BR, Hannah-Shmouni F, Nath A, Toro C, Gahl WA, Estrada-Veras JI, Dave RH. Neurological manifestations of Erdheim-Chester Disease. Ann Clin Transl Neurol 2020; 7:497-506. [PMID: 32227455 PMCID: PMC7187721 DOI: 10.1002/acn3.51014] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2019] [Revised: 02/27/2020] [Accepted: 02/27/2020] [Indexed: 12/22/2022] Open
Abstract
Objective To characterize the spectrum of neurologic involvement in Erdheim–Chester Disease (ECD), a treatable inflammatory neoplasm of histiocytes. Methods Sixty‐two patients with ECD were prospectively enrolled in a natural history study that facilitated collection of clinical, imaging, laboratory, neurophysiologic, and pathologic data. Results Ninety‐four percent of the patients had neurologic abnormalities on examination or imaging, and 22% had neurologic symptoms as the initial presentation of ECD. The most common neurologic findings were cognitive impairment, peripheral neuropathy, pyramidal tract signs, cranial nerve involvement, and cerebellar ataxia. Imaging revealed atrophy and demyelination along with focal lesions that were located throughout the nervous system, dura, and extra‐axial structures. The BRAF V600E variant correlated with cerebral atrophy. Brain pathology revealed lipid‐laden, phagocytic macrophages (histiocytes) accompanied by demyelination and axonal degeneration. Interpretation In patients with ECD, neurologic morbidity is common and contributes significantly to disability. Since neurologic symptoms can be the presenting feature of ECD and, given the mean delay in ECD diagnosis is 4.2 years, it is critical that neurologists consider of ECD and other histiocytosis in patients with inflammatory, infectious, or neoplastic‐appearing white matter. Furthermore, given the broad spectrum of neurologic involvement, neurologists have an important role in a team of specialists treating ECD patients.
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78
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Burke EA, Reichard KE, Wolfe LA, Brooks BP, DiGiovanna JJ, Hadley DW, Lehky TJ, Gropman AL, Tifft CJ, Gahl WA, Toro C, Adams D. A novel frameshift mutation in SOX10 causes Waardenburg syndrome with peripheral demyelinating neuropathy, visual impairment and the absence of Hirschsprung disease. Am J Med Genet A 2020; 182:1278-1283. [PMID: 32150337 DOI: 10.1002/ajmg.a.61542] [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: 11/14/2019] [Revised: 01/31/2020] [Accepted: 02/14/2020] [Indexed: 11/09/2022]
Abstract
Waardenburg syndrome (WS) is a group of genetic disorders associated with varying components of sensorineural hearing loss and abnormal pigmentation of the hair, skin, and eyes. There exist four different WS subtypes, each defined by the absence or presence of additional features. One of the genes associated with WS is SOX10, a key transcription factor for the development of neural crest-derived lineages. Here we report a 12-year-old boy with a novel de novo SOX10 frameshift mutation and unique combination of clinical features including primary peripheral demyelinating neuropathy, hearing loss and visual impairment but absence of Hirschsprung disease and the typical pigmentary changes of hair or skin. This expands the spectrum of currently recognized phenotypes associated with WS and illustrates the phenotypic heterogeneity of SOX10-associated WS.
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Huizing M, Malicdan MCV, Wang JA, Pri-Chen H, Hess RA, Fischer R, O'Brien KJ, Merideth MA, Gahl WA, Gochuico BR. Hermansky-Pudlak syndrome: Mutation update. Hum Mutat 2020; 41:543-580. [PMID: 31898847 DOI: 10.1002/humu.23968] [Citation(s) in RCA: 57] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2019] [Revised: 12/06/2019] [Accepted: 12/26/2019] [Indexed: 12/14/2022]
Abstract
Hermansky-Pudlak syndrome (HPS) is a group of 10 autosomal recessive multisystem disorders, each defined by the deficiency of a specific gene. HPS-associated genes encode components of four ubiquitously expressed protein complexes: Adaptor protein-3 (AP-3) and biogenesis of lysosome-related organelles complex-1 (BLOC-1) through -3. All individuals with HPS exhibit albinism and a bleeding diathesis; additional features occur depending on the defective protein complex. Pulmonary fibrosis is associated with AP-3 and BLOC-3 deficiency, immunodeficiency with AP-3 defects, and gastrointestinal symptoms are more prevalent and severe in BLOC-3 deficiency. Therefore, identification of the HPS subtype is valuable for prognosis, clinical management, and treatment options. The prevalence of HPS is estimated at 1-9 per 1,000,000. Here we summarize 264 reported and novel variants in 10 HPS genes and estimate that ~333 Puerto Rican HPS subjects and ~385 with other ethnicities are reported to date. We provide pathogenicity predictions for missense and splice site variants and list variants with high minor allele frequencies. Current cellular and clinical aspects of HPS are also summarized. This review can serve as a manifest for molecular diagnostics and genetic counseling aspects of HPS.
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Fang M, Xu X, Zhang M, Shi Y, Gu G, Liu W, Class B, Ciccone C, Gahl WA, Huizing M, Carrillo N, Wang AQ. Quantitation of cytidine-5'-monophospho-N-acetylneuraminic acid in human leukocytes using LC-MS/MS: method development and validation. Biomed Chromatogr 2020; 34:e4735. [PMID: 31691999 DOI: 10.1002/bmc.4735] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2019] [Revised: 10/18/2019] [Accepted: 10/21/2019] [Indexed: 11/06/2022]
Abstract
The biosynthesis of sialic acid (Neu5Ac) leads to the intracellular production of cytidine-5'-monophospho-N-acetylneuraminic acid (CMP-Neu5Ac), the active sialic acid donor to nascent glycans (glycoproteins and glycolipids) in the Golgi. UDP-N-acetylglucosamine 2-epimerase/N-acetylmannosamine kinase myopathy is a rare autosomal recessive muscular disease characterized by progressive muscle weakness and atrophy. To quantify the intracellular levels of CMP-Neu5Ac as well as N-acetylmannosamine (ManNAc) and Neu5Ac in human leukocytes, we developed and validated robust liquid chromatography-tandem mass spectrometry methods. A fit-for-purpose approach was implemented for method validation. Hydrophilic interaction chromatography was used to retain three hydrophilic analytes. The human leukocyte pellets were lysed and extracted in a methanol-water mixture and the leukocyte extract was used for LC-MS/MS analysis. The lower limits of quantitation for ManNAc, Neu5Ac and CMP-Neu5Ac were 25.0, 25.0 and 10.0 ng/ml, respectively. These validated methods were applied to a clinical study.
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81
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Gochuico BR, Ziegler SG, Ten NS, Balanda NJ, Mason CE, Zumbo P, Evans CA, Van Waes C, Gahl WA, Malicdan MCV. A comprehensive, multidisciplinary, precision medicine approach to discover effective therapy for an undiagnosed, progressive, fibroinflammatory disease. Transl Res 2020; 215:31-40. [PMID: 31520587 PMCID: PMC6939610 DOI: 10.1016/j.trsl.2019.08.008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/02/2019] [Revised: 08/15/2019] [Accepted: 08/22/2019] [Indexed: 11/21/2022]
Abstract
Precision medicine has generated diagnoses for many patients with challenging undiagnosed disorders. Some individuals remain without a diagnosis despite comprehensive testing, and this impedes their treatment. This report addresses the role of personalized medicine in identifying effective therapy for an undiagnosed disease. A 22-year-old woman presented with chronic severe recurrent trismus, facial pain, progressive multicentric inflammatory and fibrotic masses, and high C-reactive protein. Sites of disease included the pterygomaxillary region, masseter muscles, mandible, lung, pericardium, intrabdominal cavity, and retroperitoneum. A diagnosis was not established after an extensive assessment, including multiple biopsies. The patient was subsequently evaluated under the Undiagnosed Diseases Program at the National Institutes of Health. Large scale genotyping, proteomic studies, and in vitro and gene expression analyses of fibroblasts obtained from a major disease locus were performed. Germline genetic testing did not identify strong candidate genes; proteomic studies of the patient's serum and bronchoalveolar lavage fluid and gene expression analyses of her cells were consistent with dysregulation of the tumor necrosis factor-alpha pathway. The patient's cultured fibroblasts were incubated with selected drugs, and cell proliferation was inhibited by hydroxychloroquine. Treatment of the patient with hydroxychloroquine conferred prolonged beneficial clinical effects, including stabilization of trismus and reduction of corticosteroid dose, C-reactive protein, and size of masses. This case represents an example of precision medicine applied to discover effective treatments for individuals with enigmatic undiagnosed disorders.
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Hohenfellner K, Bergmann C, Fleige T, Janzen N, Burggraf S, Olgemöller B, Gahl WA, Czibere L, Froschauer S, Röschinger W, Vill K, Harms E, Nennstiel U. Molecular based newborn screening in Germany: Follow-up for cystinosis. Mol Genet Metab Rep 2019; 21:100514. [PMID: 31641587 PMCID: PMC6796768 DOI: 10.1016/j.ymgmr.2019.100514] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2019] [Accepted: 08/29/2019] [Indexed: 01/03/2023] Open
Abstract
BACKGROUND Newborn screening (NBS) programs for treatable metabolic disorders have been enormously successful, but molecular-based screening has not been broadly implemented so far. METHODS This prospective pilot study was performed within the German NBS framework. DNA, extracted from dried blood cards was collected as part of the regular NBS program. As cystinosis has a prevalence of only 1:100,000-1:200,000, a molecular genetic assay for detection of the SMN1 gene mutation with a higher prevalence was also included in the screening process, a genetic defect that leads to spinal muscular atrophy (SMA). First tier multiplex PCR was employed for both diseases. The cystinosis screening employed assays for the three most common CTNS mutations covering 75% of German patients; in case of heterozygosity for one of these mutations, samples were screened by next generation sequencing (NGS) of the CTNS exons for 101 CTNS mutations. A detection rate of 98.5% is predicted using this approach. RESULTS Between January 15, 2018 and May 31, 2019, 257,734 newborns were screened in Germany for cystinosis. One neonate was diagnosed with cystinosis, consistent with the known incidence of the disease. No false positive or false negatives were detected so far. Screening, communication of findings to parents, and confirmation of diagnosis were accomplished in a multi-disciplinary setting. This program was accomplished with the cooperation of hospitals, physicians, and parents. In the neonate diagnosed with cystinosis, oral cysteamine treatment began on day 18. After 16 months of treatment the child has no clinical signs of renal tubular Fanconi syndrome. CONCLUSIONS This pilot study demonstrates the efficacy of a molecular-based neonatal screening program for cystinosis using an existing national screening framework.
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Johnson TP, Larman HB, Lee MH, Whitehead SS, Kowalak J, Toro C, Lau CC, Kim J, Johnson KR, Reoma LB, Faustin A, Pardo CA, Kottapalli S, Howard J, Monaco D, Weisfeld-Adams J, Blackstone C, Galetta S, Snuderl M, Gahl WA, Kister I, Nath A. Chronic Dengue Virus Panencephalitis in a Patient with Progressive Dementia with Extrapyramidal Features. Ann Neurol 2019; 86:695-703. [PMID: 31461177 DOI: 10.1002/ana.25588] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2019] [Revised: 08/16/2019] [Accepted: 08/25/2019] [Indexed: 01/10/2023]
Abstract
OBJECTIVE To determine the underlying etiology in a patient with progressive dementia with extrapyramidal signs and chronic inflammation referred to the National Institutes of Health Undiagnosed Diseases Program. METHODS Extensive investigations included metabolic profile, autoantibody panel, infectious etiologies, genetic screening, whole exome sequencing, and the phage-display assay, VirScan, for viral immune responses. An etiological diagnosis was established postmortem. RESULTS Using VirScan, enrichment of dengue viral antibodies was detected in cerebrospinal fluid as compared to serum. No virus was detected in serum or cerebrospinal fluid, but postmortem analysis confirmed dengue virus in the brain by immunohistochemistry, in situ hybridization, quantitative polymerase chain reaction, and sequencing. Dengue virus was also detectable by polymerase chain reaction and sequencing from brain biopsy tissue collected 33 months antemortem, confirming a chronic infection despite a robust immune response directed against the virus. Immunoprofiling and whole exome sequencing of the patient did not reveal any immunodeficiency, and sequencing of the virus demonstrated wild-type dengue virus in the central nervous system. INTERPRETATION Dengue virus is the most common arbovirus worldwide and represents a significant public health concern. Infections with dengue virus are usually self-limiting, and chronic dengue infections have not been previously reported. Our findings suggest that dengue virus infections may persist in the central nervous system causing a panencephalitis and should be considered in patients with progressive dementia with extrapyramidal features in endemic regions or with relevant travel history. Furthermore, this work highlights the utility of comprehensive antibody profiling assays to aid in the diagnosis of encephalitis of unknown etiology. ANN NEUROL 2019;86:695-703.
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Hohenfellner K, Rauch F, Ariceta G, Awan A, Bacchetta J, Bergmann C, Bechtold S, Cassidy N, Deschenes G, Elenberg E, Gahl WA, Greil O, Harms E, Herzig N, Hoppe B, Koeppl C, Lewis MA, Levtchenko E, Nesterova G, Santos F, Schlingmann KP, Servais A, Soliman NA, Steidle G, Sweeney C, Treikauskas U, Topaloglu R, Tsygin A, Veys K, v. Vigier R, Zustin J, Haffner D. Management of bone disease in cystinosis: Statement from an international conference. J Inherit Metab Dis 2019; 42:1019-1029. [PMID: 31177550 PMCID: PMC7379238 DOI: 10.1002/jimd.12134] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/25/2019] [Revised: 06/02/2019] [Accepted: 06/03/2019] [Indexed: 01/10/2023]
Abstract
Cystinosis is an autosomal recessive storage disease due to impaired transport of cystine out of lysosomes. Since the accumulation of intracellular cystine affects all organs and tissues, the management of cystinosis requires a specialized multidisciplinary team consisting of pediatricians, nephrologists, nutritionists, ophthalmologists, endocrinologists, neurologists' geneticists, and orthopedic surgeons. Treatment with cysteamine can delay or prevent most clinical manifestations of cystinosis, except the renal Fanconi syndrome. Virtually all individuals with classical, nephropathic cystinosis suffer from cystinosis metabolic bone disease (CMBD), related to the renal Fanconi syndrome in infancy and progressive chronic kidney disease (CKD) later in life. Manifestations of CMBD include hypophosphatemic rickets in infancy, and renal osteodystrophy associated with CKD resulting in bone deformities, osteomalacia, osteoporosis, fractures, and short stature. Assessment of CMBD involves monitoring growth, leg deformities, blood levels of phosphate, electrolytes, bicarbonate, calcium, and alkaline phosphatase, periodically obtaining bone radiographs, determining levels of critical hormones and vitamins, such as thyroid hormone, parathyroid hormone, 25(OH) vitamin D, and testosterone in males, and surveillance for nonrenal complications of cystinosis such as myopathy. Treatment includes replacement of urinary losses, cystine depletion with oral cysteamine, vitamin D, hormone replacement, physical therapy, and corrective orthopedic surgery. The recommendations in this article came from an expert meeting on CMBD that took place in Salzburg, Austria, in December 2016.
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Pode-Shakked B, Heimer G, Vilboux T, Marek-Yagel D, Ben-Zeev B, Davids M, Ferreira CR, Philosoph AM, Veber A, Pode-Shakked N, Kenet G, Soudack M, Hoffmann C, Vernitsky H, Safaniev M, Lodzki M, Lahad A, Shouval DS, Levinkopf D, Weiss B, Barg AA, Daka A, Amariglio N, Malicdan MCV, Gahl WA, Anikster Y. Cerebral and portal vein thrombosis, macrocephaly and atypical absence seizures in Glycosylphosphatidyl inositol deficiency due to a PIGM promoter mutation. Mol Genet Metab 2019; 128:151-161. [PMID: 31445883 PMCID: PMC10569059 DOI: 10.1016/j.ymgme.2019.08.003] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/17/2019] [Revised: 08/12/2019] [Accepted: 08/13/2019] [Indexed: 10/26/2022]
Abstract
Defects of the glycosylphosphatidylinositol (GPI) biosynthesis pathway constitute an emerging subgroup of congenital disorders of glycosylation with heterogeneous phenotypes. A mutation in the promoter of PIGM, resulting in a syndrome with portal vein thrombosis and persistent absence seizures, was previously described in three patients. We now report four additional patients in two unrelated families, with further clinical, biochemical and molecular delineation of this unique entity. We also describe the first prenatal diagnosis of PIGM deficiency, allowing characterization of the natural history of the disease from birth. The patients described herein expand the phenotypic spectrum of PIGM deficiency to include macrocephaly and infantile-onset cerebrovascular thrombotic events. Finally, we offer insights regarding targeted treatment of this rare disorder with sodium phenylbutyrate.
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Torkzaban M, Haddad A, Baxter JK, Berghella V, Gahl WA, Al-Kouatly HB. Maternal ornithine transcarbamylase deficiency, a genetic condition associated with high maternal and neonatal mortality every clinician should know: A systematic review. Am J Med Genet A 2019; 179:2091-2100. [PMID: 31441224 DOI: 10.1002/ajmg.a.61329] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2019] [Revised: 07/25/2019] [Accepted: 07/29/2019] [Indexed: 12/30/2022]
Abstract
Ornithine transcarbamylase deficiency (OTCD) is a rare X-linked urea cycle disorder. Maternal OTCD can lead to life-threatening hyperammonemia if untreated. We aimed to compare the outcomes of maternal OTCD when diagnosis is known prior to pregnancy to when diagnosis is made during pregnancy. We performed a systematic literature review on maternal OTCD using the databases Ovid MEDLINE and PubMed from 1982 through 2018. Studies were included if addressed maternal OTCD signs, symptoms, and detailed pregnancy outcomes. We calculated the median or the mean for continuous variables and percentages for categorical variables. Of 36 cases of maternal OTCD, 20 (55%) were diagnosed prior to pregnancy while 16 (45%) were not. In the 20 patients diagnosed prior to pregnancy, 7 (35%) had either a neurologic or psychiatric presentation during pregnancy or postpartum. Two hyperammonemic patients (11%) experienced ICU admission, dialysis, and coma with no maternal deaths. All had a favorable outcome. In the 16 patients not known to have maternal OTCD prior to pregnancy, 13 (81%) had neurologic or psychiatric presentation during pregnancy or postpartum. Four presented with hyperemesis gravidarum. Eleven (69%) hyperammonemic patients had ICU admission and coma and 7 (47%) of them had dialysis. There were 5 (31%) maternal deaths. Three patients (19%) had prolonged hospitalization course. Overall, three male neonatal deaths were reported. Three other male children had liver transplant. Maternal OTCD is associated with high maternal and neonatal morbidity and mortality when diagnosis is made during pregnancy compared to when diagnosis is known prior to pregnancy.
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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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Ng BG, Sosicka P, Agadi S, Almannai M, Bacino CA, Barone R, Botto LD, Burton JE, Carlston C, Hon-Yin Chung B, Cohen JS, Coman D, Dipple KM, Dorrani N, Dobyns WB, Elias AF, Epstein L, Gahl WA, Garozzo D, Hammer TB, Haven J, Héron D, Herzog M, Hoganson GE, Hunter JM, Jain M, Juusola J, Lakhani S, Lee H, Lee J, Lewis K, Longo N, Lourenço CM, Mak CC, McKnight D, Mendelsohn BA, Mignot C, Mirzaa G, Mitchell W, Muhle H, Nelson SF, Olczak M, Palmer CG, Partikian A, Patterson MC, Pierson TM, Quinonez SC, Regan BM, Ross ME, Guillen Sacoto MJ, Scaglia F, Scheffer IE, Segal D, Shah Singhal N, Striano P, Sturiale L, Symonds JD, Tang S, Vilain E, Willis M, Wolfe LA, Yang H, Yano S, Powis Z, Suchy SF, Rosenfeld JA, Edmondson AC, Grunewald S, Freeze HH. SLC35A2-CDG: Functional characterization, expanded molecular, clinical, and biochemical phenotypes of 30 unreported Individuals. Hum Mutat 2019; 40:908-925. [PMID: 30817854 PMCID: PMC6661012 DOI: 10.1002/humu.23731] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2018] [Revised: 02/11/2019] [Accepted: 02/20/2019] [Indexed: 12/15/2022]
Abstract
Pathogenic de novo variants in the X-linked gene SLC35A2 encoding the major Golgi-localized UDP-galactose transporter required for proper protein and lipid glycosylation cause a rare type of congenital disorder of glycosylation known as SLC35A2-congenital disorders of glycosylation (CDG; formerly CDG-IIm). To date, 29 unique de novo variants from 32 unrelated individuals have been described in the literature. The majority of affected individuals are primarily characterized by varying degrees of neurological impairments with or without skeletal abnormalities. Surprisingly, most affected individuals do not show abnormalities in serum transferrin N-glycosylation, a common biomarker for most types of CDG. Here we present data characterizing 30 individuals and add 26 new variants, the single largest study involving SLC35A2-CDG. The great majority of these individuals had normal transferrin glycosylation. In addition, expanding the molecular and clinical spectrum of this rare disorder, we developed a robust and reliable biochemical assay to assess SLC35A2-dependent UDP-galactose transport activity in primary fibroblasts. Finally, we show that transport activity is directly correlated to the ratio of wild-type to mutant alleles in fibroblasts from affected individuals.
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Huizing M, Yardeni T, Fuentes F, Malicdan MCV, Leoyklang P, Volkov A, Dekel B, Brede E, Blake J, Powell A, Chatrathi H, Anikster Y, Carrillo N, Gahl WA, Kopp JB. Rationale and Design for a Phase 1 Study of N-Acetylmannosamine for Primary Glomerular Diseases. Kidney Int Rep 2019; 4:1454-1462. [PMID: 31701055 PMCID: PMC6829193 DOI: 10.1016/j.ekir.2019.06.012] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2019] [Revised: 06/12/2019] [Accepted: 06/17/2019] [Indexed: 12/29/2022] Open
Abstract
Introduction Sialic acids are important contributors to the polyanionic component of the glomerular filtration barrier, which regulates permeability selectivity. Pathologic glomerular hyposialylation, associated with podocyte effacement, has been implicated in human and mouse glomerulopathies. Oral treatment with N-acetylmannosamine (ManNAc), the uncharged precursor of sialic acid, ameliorates glomerular pathology in different models of glomerular disease. Methods Here we explore the sialylation status of kidney biopsies obtained from 27 subjects with various glomerular diseases using lectin histochemistry. Results We identified severe glomerular hyposialylation in 26% of the biopsies. These preliminary findings suggest that this condition may occur relatively frequently and may be a novel target for therapy. We describe the background, rationale, and design of a phase 1 study to test safety, tolerability, and pharmacokinetics of ManNAc in subjects with primary podocyte diseases. Conclusion We recently demonstrated that ManNAc was safe and well tolerated in a first-in-human phase 1 study in subjects with UDP-N-acetylglucosamine (GlcNAc) 2-epimerase/ManNAc kinase (GNE) myopathy, a disorder of impaired sialic acid synthesis. Using previous preclinical and clinical data, we propose to test ManNAc therapy for subjects with primary glomerular diseases. Even though the exact mechanisms, affected cell types, and pathologic consequences of glomerular hyposialylation need further study, treatment with this physiological monosaccharide could potentially replace or supplement existing glomerular diseases therapies.
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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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91
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Sharma P, Reichert M, Lu Y, Markello TC, Adams DR, Steinbach PJ, Fuqua BK, Parisi X, Kaler SG, Vulpe CD, Anderson GJ, Gahl WA, Malicdan MCV. Biallelic HEPHL1 variants impair ferroxidase activity and cause an abnormal hair phenotype. PLoS Genet 2019; 15:e1008143. [PMID: 31125343 PMCID: PMC6534290 DOI: 10.1371/journal.pgen.1008143] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2018] [Accepted: 04/16/2019] [Indexed: 11/18/2022] Open
Abstract
Maintenance of the correct redox status of iron is functionally important for critical biological processes. Multicopper ferroxidases play an important role in oxidizing ferrous iron, released from the cells, into ferric iron, which is subsequently distributed by transferrin. Two well-characterized ferroxidases, ceruloplasmin (CP) and hephaestin (HEPH) facilitate this reaction in different tissues. Recently, a novel ferroxidase, Hephaestin like 1 (HEPHL1), also known as zyklopen, was identified. Here we report a child with compound heterozygous mutations in HEPHL1 (NM_001098672) who presented with abnormal hair (pili torti and trichorrhexis nodosa) and cognitive dysfunction. The maternal missense mutation affected mRNA splicing, leading to skipping of exon 5 and causing an in-frame deletion of 85 amino acids (c.809_1063del; p.Leu271_ala355del). The paternal mutation (c.3176T>C; p.Met1059Thr) changed a highly conserved methionine that is part of a typical type I copper binding site in HEPHL1. We demonstrated that HEPHL1 has ferroxidase activity and that the patient's two mutations exhibited loss of this ferroxidase activity. Consistent with these findings, the patient's fibroblasts accumulated intracellular iron and exhibited reduced activity of the copper-dependent enzyme, lysyl oxidase. These results suggest that the patient's biallelic variants are loss-of-function mutations. Hence, we generated a Hephl1 knockout mouse model that was viable and had curly whiskers, consistent with the hair phenotype in our patient. These results enhance our understanding of the function of HEPHL1 and implicate altered ferroxidase activity in hair growth and hair disorders.
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92
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Benson LA, Li H, Henderson LA, Solomon IH, Soldatos A, Murphy J, Bielekova B, Kennedy AL, Rivkin MJ, Davies KJ, Hsu AP, Holland SM, Gahl WA, Sundel RP, Lehmann LE, Lee MA, Alexandrescu S, Degar BA, Duncan CN, Gorman MP. Pediatric CNS-isolated hemophagocytic lymphohistiocytosis. NEUROLOGY-NEUROIMMUNOLOGY & NEUROINFLAMMATION 2019; 6:e560. [PMID: 31044148 PMCID: PMC6467688 DOI: 10.1212/nxi.0000000000000560] [Citation(s) in RCA: 47] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/08/2019] [Accepted: 02/15/2019] [Indexed: 11/15/2022]
Abstract
Objective To highlight a novel, treatable syndrome, we report 4 patients with CNS-isolated inflammation associated with familial hemophagocytic lymphohistiocytosis (FHL) gene mutations (CNS-FHL). Methods Retrospective chart review. Results Patients with CNS-FHL are characterized by chronic inflammation restricted to the CNS that is not attributable to any previously described neuroinflammatory etiology and have germline mutations in known FHL-associated genes with no signs of systemic inflammation. Hematopoietic stem cell transplantation (HCT) can be well tolerated and effective in achieving or maintaining disease remission in patients with CNS-FHL. Conclusions Early and accurate diagnosis followed by treatment with HCT can reduce morbidity and mortality in CNS-FHL, a novel, treatable syndrome. Classification of evidence This study provides Class IV evidence that HCT is well tolerated and effective in treating CNS-FHL.
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93
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Kuo ME, Theil AF, Kievit A, Malicdan MC, Introne WJ, Christian T, Verheijen FW, Smith DEC, Mendes MI, Hussaarts-Odijk L, van der Meijden E, van Slegtenhorst M, Wilke M, Vermeulen W, Raams A, Groden C, Shimada S, Meyer-Schuman R, Hou YM, Gahl WA, Antonellis A, Salomons GS, Mancini GMS. Cysteinyl-tRNA Synthetase Mutations Cause a Multi-System, Recessive Disease That Includes Microcephaly, Developmental Delay, and Brittle Hair and Nails. Am J Hum Genet 2019; 104:520-529. [PMID: 30824121 DOI: 10.1016/j.ajhg.2019.01.006] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2018] [Accepted: 01/15/2019] [Indexed: 02/06/2023] Open
Abstract
Aminoacyl-tRNA synthetases (ARSs) are essential enzymes responsible for charging tRNA molecules with cognate amino acids. Consistent with the essential function and ubiquitous expression of ARSs, mutations in 32 of the 37 ARS-encoding loci cause severe, early-onset recessive phenotypes. Previous genetic and functional data suggest a loss-of-function mechanism; however, our understanding of the allelic and locus heterogeneity of ARS-related disease is incomplete. Cysteinyl-tRNA synthetase (CARS) encodes the enzyme that charges tRNACys with cysteine in the cytoplasm. To date, CARS variants have not been implicated in any human disease phenotype. Here, we report on four subjects from three families with complex syndromes that include microcephaly, developmental delay, and brittle hair and nails. Each affected person carries bi-allelic CARS variants: one individual is compound heterozygous for c.1138C>T (p.Gln380∗) and c.1022G>A (p.Arg341His), two related individuals are compound heterozygous for c.1076C>T (p.Ser359Leu) and c.1199T>A (p.Leu400Gln), and one individual is homozygous for c.2061dup (p.Ser688Glnfs∗2). Measurement of protein abundance, yeast complementation assays, and assessments of tRNA charging indicate that each CARS variant causes a loss-of-function effect. Compared to subjects with previously reported ARS-related diseases, individuals with bi-allelic CARS variants are unique in presenting with a brittle-hair-and-nail phenotype, which most likely reflects the high cysteine content in human keratins. In sum, our efforts implicate CARS variants in human inherited disease, expand the locus and clinical heterogeneity of ARS-related clinical phenotypes, and further support impaired tRNA charging as the primary mechanism of recessive ARS-related disease.
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Torres A, Brownstein CA, Tembulkar SK, Graber K, Genetti C, Kleiman RJ, Sweadner K, Liu KX, Mavros C, Smedemark-Margulies N, Agrawal PB, Shi J, Beggs AH, D'Angelo E, Lincoln SH, Carroll D, Dedeoglu F, Gahl WA, Biggs CM, Swoboda KJ, Berry GT, Gonzalez-Heydrich J. Withdrawn Article. Mol Genet Metab Rep 2019. [DOI: 10.1016/j.ymgmr.2017.03.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
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Mashimo M, Bu X, Aoyama K, Kato J, Ishiwata-Endo H, Stevens LA, Kasamatsu A, Wolfe LA, Toro C, Adams D, Markello T, Gahl WA, Moss J. PARP1 inhibition alleviates injury in ARH3-deficient mice and human cells. JCI Insight 2019; 4:124519. [PMID: 30830864 DOI: 10.1172/jci.insight.124519] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2018] [Accepted: 01/11/2019] [Indexed: 12/11/2022] Open
Abstract
Poly(ADP-ribosyl)ation refers to the covalent attachment of ADP-ribose to protein, generating branched, long chains of ADP-ribose moieties, known as poly(ADP-ribose) (PAR). Poly(ADP-ribose) polymerase 1 (PARP1) is the main polymerase and acceptor of PAR in response to DNA damage. Excessive intracellular PAR accumulation due to PARP1 activation leads cell death in a pathway known as parthanatos. PAR degradation is mainly controlled by poly(ADP-ribose) glycohydrolase (PARG) and ADP-ribose-acceptor hydrolase 3 (ARH3). Our previous results demonstrated that ARH3 confers protection against hydrogen peroxide (H2O2) exposure, by lowering cytosolic and nuclear PAR levels and preventing apoptosis-inducing factor (AIF) nuclear translocation. We identified a family with an ARH3 gene mutation that resulted in a truncated, inactive protein. The 8-year-old proband exhibited a progressive neurodegeneration phenotype. In addition, parthanatos was observed in neurons of the patient's deceased sibling, and an older sibling exhibited a mild behavioral phenotype. Consistent with the previous findings, the patient's fibroblasts and ARH3-deficient mice were more sensitive, respectively, to H2O2 stress and cerebral ischemia/reperfusion-induced PAR accumulation and cell death. Further, PARP1 inhibition alleviated cell death and injury resulting from oxidative stress and ischemia/reperfusion. PARP1 inhibitors may attenuate the progression of neurodegeneration in affected patients with ARH3 deficiency.
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Power B, Ferreira CR, Chen D, Zein WM, O'Brien KJ, Introne WJ, Stephen J, Gahl WA, Huizing M, Malicdan MCV, Adams DR, Gochuico BR. Hermansky-Pudlak syndrome and oculocutaneous albinism in Chinese children with pigmentation defects and easy bruising. Orphanet J Rare Dis 2019; 14:52. [PMID: 30791930 PMCID: PMC6385472 DOI: 10.1186/s13023-019-1023-7] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2018] [Accepted: 02/04/2019] [Indexed: 11/28/2022] Open
Abstract
Background Determining the etiology of oculocutaneous albinism is important for proper clinical management and to determine prognosis. The purpose of this study was to genotype and phenotype eight adopted Chinese children who presented with oculocutaneous albinism and easy bruisability. Results The patients were evaluated at a single center; their ages ranged from 3 to 8 years. Whole exome or direct sequencing showed that two of the children had Hermansky-Pudlak syndrome (HPS) type-1 (HPS-1), one had HPS-3, one had HPS-4, and four had non-syndromic oculocutaneous albinism associated with TYR variants (OCA1). Two frameshift variants in HPS1 (c.9delC and c.1477delA), one nonsense in HPS4 (c.416G > A), and one missense variant in TYR (c.1235C > T) were unreported. The child with HPS-4 is the first case with this subtype reported in the Chinese population. Hypopigmentation in patients with HPS was mild compared to that in OCA1 cases, who had severe pigment defects. Bruises, which may be more visible in patients with hypopigmentation, were found in all cases with either HPS or OCA1. Whole mount transmission electron microscopy demonstrated absent platelet dense granules in the HPS cases; up to 1.9 mean dense granules per platelet were found in those with OCA1. Platelet aggregation studies in OCA1 cases were inconclusive. Conclusions Clinical manifestations of oculocutaneous albinism and easy bruisability may be observed in children with HPS or OCA1. Establishing definitive diagnoses in children presenting with these phenotypic features is facilitated by genetic testing. Non-syndromic oculocutaneous albinism and various HPS subtypes, including HPS-4, are found in children of Chinese ancestry.
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Chin JJ, Behnam B, Davids M, Sharma P, Zein WM, Wang C, Chepa-Lotrea X, Gallantine WB, Toro C, Adams DR, Tifft CJ, Gahl WA, Malicdan MCV. Novel mutations in CLN6 cause late-infantile neuronal ceroid lipofuscinosis without visual impairment in two unrelated patients. Mol Genet Metab 2019; 126:188-195. [PMID: 30528883 DOI: 10.1016/j.ymgme.2018.12.001] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/27/2018] [Revised: 12/02/2018] [Accepted: 12/02/2018] [Indexed: 12/25/2022]
Abstract
CLN6 is a transmembrane protein located in the endoplasmic reticulum that is involved in lysosomal acidification. Mutations in CLN6 cause late-infantile neuronal ceroid lipofuscinosis (LINCL), and teenage and adult onset NCL without visual impairment. Here we describe two pediatric patients with LINCL from unrelated families who were evaluated at the National Institutes of Health. Both children exhibited typical phenotypes associated with LINCL except that they lacked the expected visual impairment. Whole exome sequencing identified novel biallelic mutations in CLN6, i.e., c.218-220dupGGT (p.Trp73dup) and c.296A > G (p.Lys99Arg) in Proband 1 and homozygous c.723G > T (p.Met241Ile) in Proband 2. Expression analysis in dermal fibroblasts showed a small increase in CLN6 protein levels. Electron micrographs of these fibroblasts demonstrated large numbers of small membrane-bound vesicles, in addition to lipofuscin deposits. LysoTracker™ Red intensity was increased in fibroblasts from both patients. This study supports a role for CLN6 in lysosomal homeostasis, and highlights the importance of considering CLN6 mutations in the diagnosis of Batten Disease even in patients with normal vision.
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Gu F, Wu A, Gordon MG, Vlahos L, Macnamara S, Burke E, Malicdan MC, Adams DR, Tifft CJ, Toro C, Gahl WA, Markello TC. A suite of automated sequence analyses reduces the number of candidate deleterious variants and reveals a difference between probands and unaffected siblings. Genet Med 2019; 21:1772-1780. [PMID: 30700791 PMCID: PMC6669106 DOI: 10.1038/s41436-019-0434-0] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2018] [Accepted: 01/03/2019] [Indexed: 12/31/2022] Open
Abstract
PURPOSE Develop an automated exome analysis workflow that can produce a very small number of candidate variants yet still detect different numbers of deleterious variants between probands and unaffected siblings. METHODS Ninety-seven outbred nuclear families from the Undiagnosed Diseases Program/Network included single probands and the corresponding unaffected sibling(s). Single-nucleotide polymorphism (SNP) chip and exome analyses were performed on all, with proband and unaffected sibling considered independently as the target. The total burden of candidate genetic variants was summed for probands and siblings over all considered disease models. RESULTS Exome analysis workflow include automated programs for ethnicity-matched genotype calling, salvage pathway for Mendelian inconsistency, compound heterozygous recessive detection, BAM file regional curation, population frequency filtering, pedigree-aware BAM file noise evaluation, and exon deletion filtration. This workflow relied heavily on BAM file analysis. A greater average pathogenic variant number was found compared with unaffected siblings. This was significant (p < 0.05) when using published recommended thresholds, and implies that causal variants are retained in many probands' lists. CONCLUSION Using Mendelian and non-Mendelian models, this agnostic exome analysis shows a difference between a small group of probands and their unaffected siblings. This workflow produces candidate lists small enough to pursue with laboratory validation.
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Klein C, Gahl WA. Patients with rare diseases: from therapeutic orphans to pioneers of personalized treatments. EMBO Mol Med 2019; 10:1-3. [PMID: 29180354 PMCID: PMC5760852 DOI: 10.15252/emmm.201708365] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Common diseases, such as cancer, diabetes mellitus, or Alzheimer's disease, affect a large segment of the population, which justifies the enormous financial allocations for translational and clinical research. In contrast, the ~5,000 known rare disorders affect only very few patients each, even though the cumulative disease burden is substantial. This influences not only the general appreciation of research to address rare diseases, but also the allocation of research funds. Importantly, however, studying rare diseases has contributed enormously to our understanding of human biochemistry, cell and developmental biology, and physiology. For example, Linus Pauling and Vernon Ingram's discovery of a structural difference and amino acid variant in the beta‐globin protein, which causes monogenic hemoglobinopathies such as sickle cell disease or thalassemia, issued in the era of molecular medicine (Pauling et al, 1949). Subsequently, numerous genetic defects in critical genes controlling differentiation and/or function of cells and organs have been identified and opened new possibilities for molecular diagnosis.
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Nmezi B, Giorgio E, Raininko R, Lehman A, Spielmann M, Koenig MK, Adejumo R, Knight M, Gavrilova R, Alturkustani M, Sharma M, Hammond R, Gahl WA, Toro C, Brusco A, Padiath QS. Genomic deletions upstream of lamin B1 lead to atypical autosomal dominant leukodystrophy. NEUROLOGY-GENETICS 2019; 5:e305. [PMID: 30842973 PMCID: PMC6384018 DOI: 10.1212/nxg.0000000000000305] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/27/2018] [Accepted: 11/06/2018] [Indexed: 11/22/2022]
Abstract
Objective Clinical, radiologic, and molecular analysis of patients with genomic deletions upstream of the LMNB1 gene. Methods Detailed neurologic, MRI examinations, custom array comparative genomic hybridization (aCGH) analysis, and expression analysis were performed in patients at different clinical centers. All procedures were approved by institutional review boards of the respective institutions. Results Five patients from 3 independent families presented at ages ranging from 32 to 52 years with neurologic symptoms that included progressive hypophonia, upper and lower limb weakness and spasticity, and cerebellar dysfunction and MRIs characterized by widespread white matter alterations. Patients had unique nonrecurrent deletions upstream of the LMNB1, varying in size from 250 kb to 670 kb. Deletion junctions were embedded in repetitive elements. Expression analysis revealed increased LMNB1 expression in patient cells. Conclusions Our findings confirmed the association between LMNB1 upstream deletions and leukodystrophy previously reported in a single family, expanding the phenotypic and molecular description of this condition. Although clinical and radiologic features overlapped with those of autosomal dominant leukodystrophy because of LMNB1 duplications, patients with deletions upstream of LMNB1 had an earlier age at symptom onset, lacked early dysautonomia, and appeared to have lesser involvement of the cerebellum and sparing of the spinal cord diameter on MRI. aCGH analysis defined a smaller minimal critical region required for disease causation and revealed that deletions occur at repetitive DNA genomic elements. Search for LMNB1 structural variants (duplications and upstream deletions) should be an integral part of the investigation of patients with autosomal dominant adult-onset leukodystrophy.
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