Tyrosyl-tRNA synthetase has a noncanonical function in actin bundling.

Dominant mutations in tyrosyl-tRNA synthetase (YARS1) and six other tRNA ligases cause Charcot-Marie-Tooth peripheral neuropathy (CMT). Loss of aminoacylation is not required for their pathogenicity, suggesting a gain-of-function disease mechanism. By an unbiased genetic screen in Drosophila, we link YARS1 dysfunction to actin cytoskeleton organization. Biochemical studies uncover yet unknown actin-bundling property of YARS1 to be enhanced by a CMT mutation, leading to actin disorganization in the Drosophila nervous system, human SH-SY5Y neuroblastoma cells, and patient-derived fibroblasts. Genetic modulation of F-actin organization improves hallmark electrophysiological and morphological features in neurons of flies expressing CMT-causing YARS1 mutations. Similar beneficial effects are observed in flies expressing a neuropathy-causing glycyl-tRNA synthetase. Hence, in this work, we show that YARS1 is an evolutionary-conserved F-actin organizer which links the actin cytoskeleton to tRNA-synthetase-induced neurodegeneration.

Evoked Potentials in Patients With Wilson Disease.

INTRODUCTION: Wilson disease (WD) is an inherited disorder of copper metabolism presenting with a variety of symptoms but commonly as a liver or neuropsychiatric disease. Abnormal evoked responses are constantly found among patients with neurologic manifestations and sometimes in patients with hepatic presentation or in presymptomatic siblings. The aim of our study was to assess visual and brainstem auditory evoked potentials (BAEP) in patients with various presentation of WD. METHODS: Visual evoked potentials (VEP) were performed in 36 WD patients and BAEP were done in 37 WD patients. RESULTS: Brainstem auditory evoked potentials were normal in patients with isolated hepatic presentation, whereas they were abnormal in 93.5% of patients with neurologic symptoms. There was significant prolongation of the latencies of the III and V waves and of the interpeak III-V and I-V latencies in comparison with the healthy controls (T-test P = 0). Abnormal VEP were observed in 81% of the patients including six of seven neurologically asymptomatic patients. The values of N75, P100, and N145 latencies were significantly longer in all patients than in healthy controls (T-test). CONCLUSIONS: The data showed that VEP and BAEP are more frequently abnormal in WD than previously reported. The abnormal VEP and BAEP even without clinical signs and brain MRI abnormalities point to subclinical involvement of visual and auditory pathways caused by copper toxicity. Because VEP and BAEP are noninvasive and widely available, they should be performed in all patents with WD.

Possible toxicity of tuberculostatic agents in a patient with a novel TYMP mutation leading to mitochondrial neurogastrointestinal encephalomyopathy.

Mitochondrial neurogastrointestinal encephalomyopathy (MNGIE) is a rare autosomal recessive multisystemic disorder caused by TYMP gene mutations. Here, we report on the first MNGIE patient diagnosed in Bulgaria who carries a novel homozygous TYMP mutation (p.Leu347Pro). The patient presented with gastrointestinal complaints, cachexia, hearing loss, ptosis, ophthalmoparesis, polyneuropathy, cognitive impairment, and leukoencephalopathy on magnetic resonance imaging (MRI) examination of the brain. The patient's motor capacity declined significantly, leading to wheelchair dependence several months following administration of tuberculostatic treatment, suggesting mitochondrial toxicity of these agents. The advanced stage of the disease and the poor medical condition prevented us from performing allogenic hematopoietic stem cell transplantation (HSCT). Early diagnosis is important not only for genetic counseling but also in view of the timely treatment with allogenic HSCT.