Pipis et al . describe the characteristics and longitudinal follow-up of 225 patients with Charcot-Marie-Tooth disease type 2A, caused by mutations in MFN2 . They describe how different mutations affect disease onset and rate of progression and identify sensitive clinical assessments that can be used for disease monitoring.

Objective Sphingolipids are enriched in the nerves. Serine‐palmitoyltransferase (SPT) catalyzes the key step of sphingolipids biosynthesis. Mutations in SPT subunits (SPTLC) lead to the excessive production of neurotoxic deoxysphingolipids (DoxSLs) in patients with Hereditary Sensory Neuropathy Type‐1C (HSN1C). HSN1C is an autosomal dominant peripheral neuropathy characterized by sensory loss and distal muscle weakness. In this study, by leveraging a HSN1C family with a previously reported N177D mutation in SPTLC2, we aim to further define the spectrum of DoxSL species and the peripheral neve pathology of the disease. Methods Next‐generation sequencing along with Sanger confirmation was performed for family members and healthy controls. LC‐MS was used for lipidomic analysis in participants’ plasma. Quantitative magnetic resonance imaging (qMRI) was performed to study sciatic nerve pathologies. Results A heterozygous N177D mutation in SPTLC2 was co‐segregated in individuals with sensory‐motor deficits in the limbs. Nerve conduction studies (NCS) revealed nonuniform slowing of conduction velocities. In line with the NCS, qMRI detected a pattern of nerve changes similar to those in acquired demyelinating polyneuropathies. Additionally, we detected a significant increase in multiple species of deoxysphingoid bases and deoxyceramides in patients’ plasma. Interpretation Mutations in the SPTLC2 cause a demyelinating phenotype resembling those in acquired demyelinating polyneuropathy. The species of increased DoxSLs in HSN1C may be more diverse than originally thought.

ObjectiveTo report novel causal mutations, expanded clinical phenotypes, and clinical management of DNA methyltransferase 1 (DNMT1)-complex disorder.MethodsNeurophysiologic testing, imaging, and genetic findings were summarized in clinical context for 5 cases with DNMT1-complex disorder.ResultsWe identified 2 novel DNMT1 mutations (p.E510K and p.P1546A) by whole-exome sequencing (WES). Case 1 (p.E510K) presented with childhood ataxia, treatment-refractory seizures, and rapid cognitive decline in his 50s. Case 2 also had childhood onset and presented with seizures, language regression, hearing loss, narcolepsy with cataplexy symptoms, optic atrophy, sensory neuropathy, and hypogammaglobulinemia requiring IV immunoglobulin. Case 2 (p.P1546A) was identified with a de novo and the first mutation residing outside the targeting sequence domain. Case 3 (p.A570V) had paralytic asymmetric onset attacks triggered by emotionality and lasting sometimes for weeks. Neuropsychological testing showed executive dysfunction localizing to frontosubcortical and frontoparietal structures. He gradually developed left predominant brain atrophy. MRI showed T2 hyperintense lesions that enhanced on T1 postgadolinium images, and brain PET showed hypometabolism in atrophied regions. Case 4 (p.T497P) underwent left cochlear implant, resulting in significant hearing improvements at all tested frequencies (250–6,000 Hz). Case 5 (p.Y511H) had profound gait ataxia with posterior column atrophy of the spinal cord and abnormal evoked potentials primarily affecting the fasciculus gracilis.ConclusionsBroader application of WES further expands genotype-phenotype correlations of DNMT1-complex disorder. Two mutations are identified with early childhood onsets. The expanded new phenotypes include asymmetric brain hemiatrophy with parenchymal gadolinium enhancement, spinal cord atrophy, prolonged cataplectic spells, and hypogammaglobulinemia. Hearing loss treatment by cochlear implantation is helpful and should be considered.

Objective Hereditary Neuropathy with Liability to Pressure Palsies (HNPP) is caused by a heterozygous deletion of peripheral myelin protein‐22 (PMP22) gene resulting in focal sensorimotor deficits. Our lab has identified a disruption of myelin junctions in excessively permeable myelin that impairs action potential propagation. This mechanism is expected to cause fatigue in patients with HNPP. Therefore, the objective was to characterize fatigue in patients with HNPP and determine the relationship of fatigue to nerve pathology, disability, and quality of life. Methods Nine females with HNPP participated in a single visit that included genotyping, nerve conduction studies, neurological exam, quantitative magnetic resonance imaging, and a physical therapy exam incorporating upper and lower extremity function and survey measures of fatigue. This visit was followed by 2 weeks of ecological momentary assessment (wrist‐worn device) that captured fatigue ratings five times per day. Results Participants demonstrated mild neurological impairment (CMTNS: 5.7 ± 2.8), yet reported high fatigue levels (average fatigue intensity over 2 weeks: 5.9 out of 10). Higher fatigue levels were associated with poorer quality of life and more pain. Higher fatigue was associated with significantly greater distal nerve proton density changes on peripheral nerve MRI, which is in line with hyper‐permeable myelin in HNPP. Interpretation Fatigue is common and severe among patients with HNPP whose disabilities are minimal by conventional outcome measures. Therapeutic interventions targeting fatigue have the potential to improve quality of life and may serve as a robust outcome measure to show longitudinal changes for patients with HNPP.

Viruses are one of the most important concerns for human health, and overcoming viral infections is a worldwide challenge. However, researchers have been trying to manipulate viral genomes to overcome various disorders, including cancer, for vaccine development purposes. CRISPR (clustered regularly interspaced short palindromic repeats) is becoming one of the most functional and widely used tools for RNA and DNA manipulation in multiple organisms. This approach has provided an unprecedented opportunity for creating simple, inexpensive, specific, targeted, accurate, and practical manipulations of viruses, such as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), human immunodeficiency virus-1 (HIV-1), and vaccinia virus. Furthermore, this method can be used to make an effective and precise diagnosis of viral infections. Nevertheless, a valid and scientifically designed CRISPR system is critical to make more effective and accurate changes in viruses. In this review, we have focused on the best and the most effective ways to design sgRNA, gene knock-in(s), and gene knock-out(s) for virus-targeted manipulation. Furthermore, we have emphasized the application of CRISPR technology in virus diagnosis and in finding significant genes involved in virus-host interactions.

Hereditary sensory and autonomic neuropathy type 1 (HSAN1/HSN1) is a peripheral neuropathy most commonly associated with pathogenic variants in the serine palmitoyltransferase complex (SPTLC1, SPTLC2) genes, which are responsible for sphingolipid biosynthesis. Recent reports have shown that some HSAN1 patients also develop macular telangiectasia type 2 (MacTel2), a retinal neurodegeneration with an enigmatic pathogenesis and complex heritability. Here, we report a novel association of a SPTLC2 c.529A>G p.(Asn177Asp) variant with MacTel2 in a single member of a family that otherwise has multiple members afflicted with HSAN1. We provide correlative data to suggest that the variable penetrance of the HSAN1/MacTel2-overlap phenotype in the proband may be explained by levels of certain deoxyceramide species, which are aberrant intermediates of sphingolipid metabolism. We provide detailed retinal imaging of the proband and his HSAN1+/MacTel2- brothers and suggest mechanisms by which deoxyceramide levels may induce retinal degeneration. This is the first report of HSAN1 vs. HSAN1/MacTel2 overlap patients to comprehensively profile sphingolipid intermediates. The biochemical data here may help shed light on the pathoetiology and molecular mechanisms of MacTel2.

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Human sciatic nerve morphometrics were measured for nerve volume, fascicle volume, and fascicle density using a 3D gradient echo sequence with an in-plane resolution of 0.15 x 0.15 mm2. Metrics from healthy controls showed a moderate correlation of nerve and fascicle volumes with body mass index but not with age. There was a strong correlation between nerve volume and the clinical score of disease severity in patients with hereditary neuropathy with liability to pressure palsies.