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ObjectiveTo identify novel disease associated loci for amyotrophic lateral sclerosis (ALS), we used sequencing data and performed in vitro and in vivo experiments to demonstrate pathogenicity of mutations identified inTP73.MethodsWe analyzed exome sequences of 87 patients with sporadic ALS and 324 controls, with confirmatory sequencing in independent ALS cohorts of >2,800 patients. For the top hit,TP73, a regulator of apoptosis and differentiation and a binding partner and homolog of the tumor suppressor geneTP53, we assayed mutation effects using in vitro and in vivo experiments. C2C12 myoblast differentiation assays, characterization of myotube appearance, and immunoprecipitation of p53-p73 complexes were performed in vitro. In vivo, we used clustered regularly interspaced short palindromic repeats (CRISPR)/Cas9 targeting of zebrafishtp73to assay motor neuron number and axon morphology.ResultsFour heterozygous rare, nonsynonymous mutations inTP73were identified in our sporadic ALS cohort. In independent ALS cohorts, we identified an additional 19 rare, deleterious variants inTP73. PatientTP73mutations caused abnormal differentiation and increased apoptosis in the myoblast differentiation assay, with abnormal myotube appearance. Immunoprecipitation of mutant ΔN-p73 demonstrated that patient mutations hinder the ability of ΔN-p73 to bind p53. CRISPR/Cas9 knockout oftp73in zebrafish led to impaired motor neuron development and abnormal axonal morphology, concordant with ALS pathology.ConclusionTogether, these results strongly suggest that variants inTP73correlate with risk for ALS and indicate a role for apoptosis in ALS disease pathology.

Objectives: Leukodystrophies are diseases of the white matter for which data concerning clinical characteristics, incidence, disease burden, and description of outcomes are sparse. The purpose of our study was to determine the incidence and most common types of inherited leukodystrophies in a population, the mortality and time course of deaths, common neurologic features in patients, and health care costs associated with leukodystrophies. Methods: We conducted a retrospective, hospital- and clinic-based surveillance of inherited leukodystrophies among children younger than 18 years presenting to a regional children9s hospital. We enrolled children evaluated from January 1, 1999, through December 31, 2007; clinical information was obtained from medical records. We calculated incidence based on state birth rates. Results: A total of 122 children with an inherited leukodystrophy were identified; 542 patients were excluded. A total of 49% had epilepsy, 43% required a gastrostomy tube, and 32% had a history of developmental regression. Mortality was 34%; average age at death was 8.2 years. No final diagnosis was reported in 51% of patients. The most common diagnoses were metachromatic leukodystrophy (8.2%), Pelizaeus-Merzbacher disease (7.4%), mitochondrial diseases (4.9%), and adrenoleukodystrophy (4.1%). Endocrine abnormalities and hypoplastic cerebellum were noted in significant portions of patients (15% and 14%). Average yearly per-patient medical costs were $22,579. Population incidence was 1 in 7,663 live births. Conclusions: Inherited leukodystrophies are associated with substantial morbidity and mortality in children. Overall population incidence is higher than generally appreciated (1 in 7,663 live births). Most leukodystrophies remain undiagnosed, but a logical algorithm based on prevalence could aid testing.

Objectives: Our objective was to determine the extent of testing and costs solely related to diagnosis (the diagnostic odyssey) in a cohort of children with inherited leukodystrophies. Methods: We determined all inpatient and outpatient laboratory testing, including brain MRIs obtained for the purpose of diagnosis, over an 8-year time period in a retrospective population cohort of children with inherited leukodystrophies. Costs were determined from an activity-based cost accounting system and were standardized to 2013 constant US dollars. Results: Each patient had on average 20 tests (range 2–42 tests), with costs of $4,200 (range $357–$15,611). Diagnostic yield plateaued after 25 tests, and costs increased significantly after 32 tests. Fifty-three percent of patients were diagnosed in 20 or fewer tests, compared with 17% if more than 20 tests were performed. Conclusions: Our findings provide details on the amount and costs of testing in children who often undergo a diagnostic odyssey. Our results suggest that diagnostic testing is a relatively modest contributor to the overall health care costs in patients with leukodystrophy, and offer insights into the diagnostic odyssey of children with neurologic impairment.

Objective: We describe a novel congenital motor neuron disease with early demise due to respiratory insufficiency with clinical overlap with spinal muscular atrophy with respiratory distress (SMARD) type 1 but lacking a mutation in the IGHMBP2 gene. Methods: Exome sequencing was used to identify a de novo mutation in the LAS1L gene in the proband. Pathogenicity of the mutation was validated using a zebrafish model by morpholino-mediated knockdown of las1l . Results: We identified a de novo mutation in the X-linked LAS1L gene in the proband (p.S477N). The mutation is in a highly conserved region of the LAS1L gene predicted to be deleterious by bioinformatic analysis. Morpholino-based knockdown of las1l , the orthologous gene in zebrafish, results in early lethality and disruption of muscle and peripheral nerve architecture. Coinjection of wild-type but not mutant human RNA results in partial rescue of the phenotype. Conclusion: We report a patient with a SMARD phenotype due to a mutation in LAS1L , a gene important in coordinating processing of the 45S pre-rRNA and maturation of the large 60S ribosomal subunit. Similarly, the IGHMB2 gene associated with SMARD type 1 has been suggested to have an important role in ribosomal biogenesis from its role in processing the 45S pre-rRNA. We propose that disruption of ribosomal maturation may be a common pathogenic mechanism linking SMARD phenotypes caused by both IGHMBP2 and LAS1L .

A 27-year-old man with acute lymphoblastic leukemia developed ataxia, dysarthria, and confusion 2 weeks after initiating metronidazole therapy for Clostridium difficile colitis. Brain MRI revealed cytotoxic edema, without contrast enhancement, in the cerebellar dentate nuclei (figure, A and B), dorsal pons, and medulla. Metronidazole …