Long-read sequencing identifies an SVA_D retrotransposon insertion deep within the intron of ATP7A as a novel cause of occipital horn syndrome.

BACKGROUND: SINE-VNTR-Alu (SVA) retrotransposons move from one genomic location to another in a 'copy-and-paste' manner. They continue to move actively and cause monogenic diseases through various mechanisms. Currently, disease-causing SVA retrotransposons are classified into human-specific young SVA_E or SVA_F subfamilies. In this study, we identified an evolutionarily old SVA_D retrotransposon as a novel cause of occipital horn syndrome (OHS). OHS is an X-linked, copper metabolism disorder caused by dysfunction of the copper transporter, ATP7A. METHODS: We investigated a 16-year-old boy with OHS whose pathogenic variant could not be detected via routine molecular genetic analyses. RESULTS: A 2.8 kb insertion was detected deep within the intron of the patient's ATP7A gene. This insertion caused aberrant mRNA splicing activated by a new donor splice site located within it. Long-read circular consensus sequencing enabled us to accurately read the entire insertion sequence, which contained highly repetitive and GC-rich segments. Consequently, the insertion was identified as an SVA_D retrotransposon. Antisense oligonucleotides (AOs) targeting the new splice site restored the expression of normal transcripts and functional ATP7A proteins. AO treatment alleviated excessive accumulation of copper in patient fibroblasts in a dose-dependent manner. Pedigree analysis revealed that the retrotransposon had moved into the OHS-causing position two generations ago. CONCLUSION: This is the first report of a human monogenic disease caused by the SVA_D retrotransposon. The fact that the evolutionarily old SVA_D is still actively transposed, leading to increased copy numbers may make a notable impact on rare genetic disease research.

Involvement of mTOR pathway in neurodegeneration in NSF-related developmental and epileptic encephalopathy.

Membrane fusion is mediated by soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) proteins. During neurotransmitter exocytosis, SNARE proteins on a synaptic vesicle and the target membrane form a complex, resulting in neurotransmitter release. N-ethylmaleimide-sensitive factor (NSF), a homohexameric ATPase, disassembles the complex, allowing individual SNARE proteins to be recycled. Recently, the association between pathogenic NSF variants and developmental and epileptic encephalopathy (DEE) was reported; however, the molecular pathomechanism of NSF-related DEE remains unclear. Here, three patients with de novo heterozygous NSF variants were presented, of which two were associated with DEE and one with a very mild phenotype. One of the DEE patients also had hypocalcemia from parathyroid hormone deficiency and neuromuscular junction impairment. Using PC12 cells, a neurosecretion model, we show that NSF with DEE-associated variants impaired the recycling of vesicular membrane proteins and vesicle enlargement in response to exocytotic stimulation. In addition, DEE-associated variants caused neurodegenerative change and defective autophagy through overactivation of the mammalian/mechanistic target of rapamycin (mTOR) pathway. Treatment with rapamycin, an mTOR inhibitor or overexpression of wild-type NSF ameliorated these phenotypes. Furthermore, neurons differentiated from patient-derived induced pluripotent stem cells showed neurite degeneration, which was also alleviated by rapamycin treatment or gene correction using genome editing. Protein structure analysis of NSF revealed that DEE-associated variants might disrupt the transmission of the conformational change of NSF monomers and consequently halt the rotation of ATP hydrolysis, indicating a dominant negative mechanism. In conclusion, this study elucidates the pathomechanism underlying NSF-related DEE and identifies a potential therapeutic approach.

Isolated sixth nerve palsy as an initial presentation of primary angiitis of the central nervous system.

BACKGROUND: Primary angiitis of the central nervous system (PACNS) is a newly-emerging disease, and it is known that early diagnosis with treatment is important for the improvement of prognosis. CASE DESCRIPTION: Here, we report the case of a previously healthy 13-year-old girl who presented with right eye abduction failure, attributed to isolated right sixth nerve palsy, as the initial symptom of PACNS. Magnetic resonance angiography (MRA) showed stenosis in the distal portion of the right internal carotid artery, and delay alternating with nutation for tailored excitation (DANTE)-prepared contrast-enhanced magnetic resonance imaging confirmed vasculitis at the same site. The patient was subsequently treated with three courses of pulse corticosteroid therapy (methylprednisolone intravenously 30 mg/kg/day for three consecutive days). Diplopia completely resolved within 3 months after three course of steroid pulse therapy, and when taking 10 mg PSL daily. Follow-up MRA confirmed complete resolution of the arterial narrowing, and no relapse was observed after 2 months of steroid cessation. DISCUSSION: This case report illustrates an unusual presentation of PACNS with isolated sixth nerve palsy. PACNS was thought to cause insults on a single cranial nerve either through local spread of inflammation or hypoxic-ischemic insults on the nerve root due to involvement of feeding microvessels. The decision to perform imaging studies in cases of isolated sixth nerve palsy remains controversial because of the possibility of spontaneous recovery. Our case supports the existing literature that recommends that even an isolated symptom of unilateral abducens nerve palsy requires timely imaging studies.

[Enteral nutrition ameliorated superior mesenteric artery syndrome in a patient with Duchenne muscular dystrophy].

The abdominal complications of Duchenne muscular dystrophy (DMD) include acute gastric dilatation, superior mesenteric artery (SMA) syndrome, ileus and constipation. We report herein a patient with DMD in whom SMA syndrome was successfully treated with enteral tube nutrition. The patient was a 16-year-old boy diagnosed with DMD at 2 years. Steroid therapy was started at 5 years, and he was unable to walk and was wheelchair-bound at 11 years. Lordoscoliosis progressed after the age of 14 years. Noninvasive mechanical ventilation was introduced due to respiratory impairment at 15 years. During 8 months with respiratory impairment, his body weight decreased from 40.3 kg to 33.4 kg. He was referred to our hospital for vomiting and hematemesis. Radiographic studies indicated a diagnosis of SMA syndrome. Enteral nutrition with a nasojejunal tube successfully treated SMA syndrome for 5 months and his body weight increased from 32.7 kg to 36.1 kg. Gastrostomy was subsequently performed and no recurrence was evident. SMA syndrome is caused by compression of the third part of the duodenum at the angle between the aorta and SMA. The conditions for duodenal vascular compression are weight loss resulting in depletion of the retroperitoneal fat and progressive lordosis. The reasons for SMA syndrome with our patient were weight loss and progressive lordoscoliosis. A conservative approach with enteral nutrition promoted weight gain, increasing retroperitoneal fat. Enteral nutrition should be considered for the treatment of SMA syndrome as a complication of DMD.

Effects and limits of acute noninvasive positive pressure ventilation in children with severe motor and intellectual disabilities with pneumonia/bronchitis.

Objective: We have frequently applied noninvasive positive pressure ventilation (NPPV) to treat acute respiratory failure in children with severe motor and intellectual disabilities. We investigated the features and causes of conditions requiring endotracheal intubation. We aimed to determine whether phlegm expulsion using appropriate breathing physiotherapy with NPPV could avoid the need for endotracheal intubation in such patients. Methods: Between December 2010 and November 2012, 21 children with 51 episodes of acute respiratory failure were placed on NPPV at our hospital. We investigated the ratio, background, and causes of conditions requiring endotracheal intubation. Results: Pneumonia and bronchitis caused 30 and 21 episodes of respiratory failure, respectively. Respiratory infection required endotracheal intubation in 8 of 30 episodes of pneumonia, and in none of the 21 episodes of bronchitis. Respiratory infections were caused by upper airway obstruction with large amounts of secretion (n=4), lower airway obstruction due to atelectasis (n=3) and a combination of both (n=1). The frequency of breathing physiotherapy was significantly higher for all patients who required assistance with active phlegm expulsion than in those who did not (p=0.006). More patients on endotracheal intubation also required phlegm aspiration compared with other patients (p=0.019). Conclusion: We applied NPPV to acute respiratory failure in children with severe motor and intellectual disabilities. This allowed 84% of them to avoid endotracheal intubation. Acute respiratory failure did not improve in any patient who required endotracheal intubation, but we also used NPPV with breathing physiotherapy and postural drainage. Assistance with phlegm expulsion is hampered in children with severe motor and intellectual disabilities due to conditions such as thoracic deformations, joint contracture and glossoptosis. We consider that assistance with phlegm expulsion using appropriate breathing physiotherapy with NPPV is very important for such patients.