Single substitution in H3.3G34 alters DNMT3A recruitment to cause progressive neurodegeneration.

Germline histone H3.3 amino acid substitutions, including H3.3G34R/V, cause severe neurodevelopmental syndromes. To understand how these mutations impact brain development, we generated H3.3G34R/V/W knock-in mice and identified strikingly distinct developmental defects for each mutation. H3.3G34R-mutants exhibited progressive microcephaly and neurodegeneration, with abnormal accumulation of disease-associated microglia and concurrent neuronal depletion. G34R severely decreased H3K36me2 on the mutant H3.3 tail, impairing recruitment of DNA methyltransferase DNMT3A and its redistribution on chromatin. These changes were concurrent with sustained expression of complement and other innate immune genes possibly through loss of non-CG (CH) methylation and silencing of neuronal gene promoters through aberrant CG methylation. Complement expression in G34R brains may lead to neuroinflammation possibly accounting for progressive neurodegeneration. Our study reveals that H3.3G34-substitutions have differential impact on the epigenome, which underlie the diverse phenotypes observed, and uncovers potential roles for H3K36me2 and DNMT3A-dependent CH-methylation in modulating synaptic pruning and neuroinflammation in post-natal brains.

Resting-state activity in development and maintenance of normal brain function.

One of the most intriguing recent discoveries concerning brain function is that intrinsic neuronal activity manifests as spontaneous fluctuations of the blood oxygen level-dependent (BOLD) functional MRI signal. These BOLD fluctuations exhibit temporal synchrony within widely distributed brain regions known as resting-state networks. Resting-state networks are present in the waking state, during sleep, and under general anesthesia, suggesting that spontaneous neuronal activity plays a fundamental role in brain function. Despite its ubiquitous presence, the physiological role of correlated, spontaneous neuronal activity remains poorly understood. One hypothesis is that this activity is critical for the development of synaptic connections and maintenance of synaptic homeostasis. We had a unique opportunity to test this hypothesis in a 5-y-old boy with severe epileptic encephalopathy. The child developed marked neurologic dysfunction in association with a seizure disorder, resulting in a 1-y period of behavioral regression and progressive loss of developmental milestones. His EEG showed a markedly abnormal pattern of high-amplitude, disorganized slow activity with frequent generalized and multifocal epileptiform discharges. Resting-state functional connectivity MRI showed reduced BOLD fluctuations and a pervasive lack of normal connectivity. The child underwent successful corpus callosotomy surgery for treatment of drop seizures. Postoperatively, the patient's behavior returned to baseline, and he resumed development of new skills. The waking EEG revealed a normal background, and functional connectivity MRI demonstrated restoration of functional connectivity architecture. These results provide evidence that intrinsic, coherent neuronal signaling may be essential to the development and maintenance of the brain's functional organization.

Disease Course and Response to Immunotherapy in Children With Childhood Disintegrative Disorder: A Retrospective Case Series.

Childhood disintegrative disorder is a poorly understood neurobehavioral disorder of early childhood characterized by acute to subacute profound regression in previously developed language, social behavior, and adaptive functions. The etiology of childhood disintegrative disorder remains unknown and treatment is focused on symptomatic management. Interest in neuroinflammatory mechanisms has grown with the increased recognition of autoimmune brain diseases and similarities between the presenting symptoms of childhood disintegrative disorder and pediatric autoimmune encephalitis. Importantly, a diagnosis of pediatric autoimmune encephalitis requires evidence of inflammation on paraclinical testing, which is absent in childhood disintegrative disorder. Here we report 5 children with childhood disintegrative disorder who were initially diagnosed with possible autoimmune encephalitis and treated with immunotherapy. Two children had provocative improvements, whereas 3 did not change significantly on immunotherapy. Additionally, a sixth patient with childhood disintegrative disorder evaluated in our Autoimmune Brain Disease Clinic showed spontaneous improvement and is included to highlight the variable natural history of childhood disintegrative disorder that may mimic treatment responsiveness.

The severity of MUSK pathogenic variants is predicted by the protein domain they disrupt.

Biallelic loss-of-function variants in the MUSK gene result in two allelic disorders: (1) congenital myasthenic syndrome (CMS; OMIM: 616325), a neuromuscular disorder that has a range of severity from severe neonatal-onset weakness to mild adult-onset weakness, and (2) fetal akinesia deformation sequence (OMIM: 208150), a form of pregnancy loss characterized by severe muscle weakness in the fetus. The MUSK gene codes for muscle-specific kinase (MuSK), a receptor tyrosine kinase involved in the development of the neuromuscular junction. Here, we report a case of neonatal-onset MUSK-related CMS in a patient harboring compound heterozygous deletions in the MUSK gene, including (1) a deletion of exons 2-3 leading to an in-frame MuSK protein lacking the immunoglobulin 1 (Ig1) domain and (2) a deletion of exons 7-11 leading to an out-of-frame, truncated MuSK protein. Individual domains of the MuSK protein have been elucidated structurally; however, a complete MuSK structure generated by machine learning algorithms has clear inaccuracies. We modify a predicted AlphaFold structure and integrate previously reported domain-specific structural data to suggest a MuSK protein that dimerizes in two locations (Ig1 and the transmembrane domain). We analyze known pathogenic variants in MUSK to discover domain-specific genotype-phenotype correlations; variants that lead to a loss of protein expression, disruption of the Ig1 domain, or Dok-7 binding are associated with the most severe phenotypes. A conceptual model is provided to explain the severe phenotypes seen in Ig1 variants and the poor response of our patient to pyridostigmine.

Limited regional cerebellar dysfunction induces focal dystonia in mice.

Dystonia is a complex neurological syndrome broadly characterized by involuntary twisting movements and abnormal postures. The anatomical distribution of the motor symptoms varies among dystonic patients and can range from focal, involving an isolated part of the body, to generalized, involving many body parts. Functional imaging studies of both focal and generalized dystonias in humans often implicate the cerebellum suggesting that similar pathological processes may underlie both. To test this, we exploited tools developed in mice to generate animals with gradients of cerebellar dysfunction. By using conditional genetics to regionally limit cerebellar dysfunction, we found that abnormalities restricted to Purkinje cells were sufficient to cause dystonia. In fact, the extent of cerebellar dysfunction determined the extent of abnormal movements. Dysfunction of the entire cerebellum caused abnormal postures of many body parts, resembling generalized dystonia. More limited regions of dysfunction that were created by electrical stimulation or conditional genetic manipulations produced abnormal movements in an isolated body part, resembling focal dystonia. Overall, these results suggest that focal and generalized dystonias may arise through similar mechanisms and therefore may be approached with similar therapeutic strategies.

Aphasia Associated With Acute on Chronic Kidney Failure in an Adolescent.

Acute and chronic kidney disease (CKD) have known neurological associations resulting from uremia, electrolyte disturbances, comorbidities such as hypertension, or other toxin accumulation. Reversible focal neurological deficits are relatively uncommon and poorly understood sequelae of kidney disease. Herein, we describe an unusual case of an adolescent male who developed acute aphasia during his initial presentation for acute kidney injury (AKI) superimposed on progressive CKD stage 5 associated with uremia and multiple electrolyte derangements. Symptoms resolved within one day of initiating continuous renal replacement therapy (CRRT) and gradual electrolyte and uremia correction. Such transient focal neurological deficits in AKI superimposed on progressive CKD in the pediatric population has not been widely reported.

Parental perspectives of episodic irritability in an ultra-rare genetic disorder associated with NACC1.

BACKGROUND: A recurrent de novo variant (c.892C>T) in NACC1 causes a neurodevelopmental disorder with epilepsy, cataracts, feeding difficulties, and delayed brain myelination (NECFM). An unusual and consistently reported feature is episodic extreme irritability and inconsolability. We now characterize these episodes, their impact on the family, and ascertain treatments that may be effective. Parents of 14 affected individuals provided narratives describing the irritability episodes, including triggers, behavioral and physiological changes, and treatments. Simultaneously, parents of 15 children completed the Non-communicating Children's Pain Checklist-Revised (NCCPC-R), a measure to assess pain in non-verbal children. RESULTS: The episodes of extreme irritability include a prodromal, peak, and resolving phase, with normal periods in between. The children were rated to have extreme pain-related behaviors on the NCCPC-R scale, although it is unknown whether the physiologic changes described by parents are caused by pain. Attempted treatments included various classes of medications, with psychotropic and sedative medications being most effective (7/15). Nearly all families (13/14) describe how the episodes have a profound impact on their lives. CONCLUSIONS: NECFM caused by the recurrent variant c.892C>T is associated with a universal feature of incapacitating episodic irritability of unclear etiology. Further understanding of the pathophysiology can lead to more effective therapeutic strategies.

Opioid and benzodiazepine use during therapeutic hypothermia in encephalopathic neonates.

OBJECTIVES: To evaluate the use of sedatives and analgesics during therapeutic hypothermia in encephalopathic neonates and assess associations between medication exposure and hospital outcomes. STUDY DESIGN: We identified neonates ≥35 weeks gestational age treated with therapeutic hypothermia at 125 neonatal intensive care units between 2007 and 2015. We compared characteristics and hospital outcomes between unexposed neonates and neonates exposed to opioids and/or benzodiazepines. RESULTS: Opioids were administered to 1 677/2 621 (64%) neonates, and exposure increased from 38% in 2008 to 68% in 2015. Sedation/analgesia varied widely between centers. Opioid-exposed neonates experienced greater durations of respiratory support and were more likely to receive inotropes and inhaled nitric oxide. Mortality during postnatal days 0-3 was lower among opioid-exposed neonates (31/625 [5%]) than unexposed neonates (64/714 [9%]). CONCLUSIONS: Sedation/analgesia during therapeutic hypothermia is prevalent but not uniform across centers. Prospective studies are needed to assess if exposure independently predicts intensity and duration of physiologic support.

The importance of managing the patient and not the gene: expanded phenotype of GLE1-associated arthrogryposis.

GLE1 encodes a protein important for mRNA export and appears to play roles in translation initiation and termination as well. Pathogenic variants in GLE1 mutations have been associated with lethal contracture syndrome and lethal arthrogryposis with anterior horn cell disease; phenotypes reported in individuals include fetal akinesia and a severe form of motor neuron disease, typically presenting with prenatal symptoms and perinatal lethality. In this article, we identified biallelic missense mutations in GLE1 by trio whole-exome sequencing in an individual affected with congenital motor weakness and contractures as well as feeding and respiratory difficulties. Muscle biopsy was consistent with anterior horn cell disease and supported the pathogenicity of the sequence variants. Importantly, this individual survived past the perinatal period with respiratory support and currently demonstrates age-appropriate cognition and slow but steady motor developmental progress. We propose that pathogenic variants in GLE1 can be associated with a nonperinatal lethal motor phenotype, and affected individuals can demonstrate motor skill progression, unlike prototypical anterior horn cell diseases such as spinal muscular atrophy.

Abnormal cerebellar signaling induces dystonia in mice.

Dystonia is a relatively common neurological syndrome characterized by twisting movements or sustained abnormal postures. Although the basal ganglia have been implicated in the expression of dystonia, recent evidence suggests that abnormal cerebellar function is also involved. In these studies, a novel mouse model was developed to study the role of the cerebellum in dystonia. Microinjection of low doses of kainic acid into the cerebellar vermis of mice elicited reliable and reproducible dystonic postures of the trunk and limbs. The severity of the dystonia increased linearly with kainate dose. Kainate-induced dystonia was blocked by the glutamatergic antagonist 1,2,3,4-tetrahydro-6-nitro-2,3-dioxo-benzo[f]quinoxaline-7-sulfonamide and reproduced by domoic acid microinjection, suggesting that the induction of dystonia is dependent on glutamatergic activation in this model. The abnormal movements were not associated with kainate-induced seizures, because EEG recordings showed no epileptiform activity during the dystonic events. Neuronal activation, as assessed by in situ hybridization for c-fos, revealed c-fos mRNA expression in the cerebellum, locus ceruleus, and red nucleus. In contrast, regions associated with epileptic seizures, such as the hippocampus, did not exhibit increased c-fos expression after cerebellar kainate injection. Furthermore, in transgenic mice lacking Purkinje cells, significantly less dystonia was induced after kainic acid injection, implicating Purkinje cells and the cerebellar cortex in this model of dystonia. Together, these data suggest that abnormal cerebellar signaling produces dystonia and that the cerebellum should be considered along with the basal ganglia in the pathophysiology of this movement disorder.

Thinner Retinal Nerve Fiber Layer in Very Preterm Versus Term Infants and Relationship to Brain Anatomy and Neurodevelopment.

PURPOSE: To assess retinal nerve fiber layer (RNFL) thickness at term-equivalent age in very preterm (<32 weeks gestational age) vs term-born infant cohorts, and compare very preterm infant RNFL thickness with brain anatomy and neurodevelopment. DESIGN: Cohort study. METHODS: RNFL was semi-automatically segmented (1 eye per infant) in 57 very preterm and 50 term infants with adequate images from bedside portable, handheld spectral-domain optical coherence tomography imaging at 37-42 weeks postmenstrual age. Mean RNFL thickness was calculated for the papillomacular bundle (-15 degrees to +15 degrees) and temporal quadrant (-45 degrees to +45 degrees) relative to the fovea-optic nerve axis. Brain magnetic resonance imaging (MRI) scans clinically obtained in 26 very preterm infants were scored for global structural abnormalities by an expert masked to data except for age. Cognitive, language, and motor skills were assessed in 33 of the very preterm infants at 18-24 months corrected age. RESULTS: RNFL was thinner for very preterm vs term infants at the papillomacular bundle ([mean ± standard deviation] 61 ± 17 vs 72 ± 13 µm, P < .001) and temporal quadrant (72 ± 21 vs 82 ± 16 µm, P = .005). In very preterm infants, thinner papillomacular bundle RNFL correlated with higher global brain MRI lesion burden index (R(2) = 0.35, P = .001) and lower cognitive (R(2) = 0.18, P = .01) and motor (R(2) = 0.17, P = .02) scores. Relationships were similar for temporal quadrant. CONCLUSIONS: Thinner RNFL in very preterm infants relative to term-born infants may relate to brain structure and neurodevelopment.

Diffuse reduction of white matter connectivity in cerebral palsy with specific vulnerability of long range fiber tracts.

Cerebral palsy (CP) is a heterogeneous group of non-progressive motor disorders caused by injury to the developing fetal or infant brain. Although the defining feature of CP is motor impairment, numerous other neurodevelopmental disabilities are associated with CP and contribute greatly to its morbidity. The relationship between brain structure and neurodevelopmental outcomes in CP is complex, and current evidence suggests that motor and developmental outcomes are related to the spatial pattern and extent of brain injury. Given that multiple disabilities are frequently associated with CP, and that there is increasing burden of neurodevelopmental disability with increasing motor severity, global white matter (WM) connectivity was examined in a cohort of 17 children with bilateral CP to test the hypothesis that increased global WM damage will be seen in the group of severely affected (Gross Motor Function Classification Scale (GMFCS) level of IV) as compared to moderately affected (GMFCS of II or III) individuals. Diffusion tensor tractography was performed and the resulting fibers between anatomically defined brain regions were quantified and analyzed in relation to GMFCS levels. Overall, a reduction in total WM connectivity throughout the brain in severe versus moderate CP was observed, including but not limited to regions associated with the sensorimotor system. Our results also show a diffuse and significant reduction in global inter-regional connectivity between severity groups, represented by inter-regional fiber count, throughout the brain. Furthermore, it was also observed that there is a significant difference (p = 0.02) in long-range connectivity in patients with severe CP as compared to those with moderate CP, whereas short-range connectivity was similar between groups. This new finding, which has not been previously reported in the CP literature, demonstrates that CP may involve distributed, network-level structural disruptions.