Motor Organization in Schizencephaly: Outcomes of Transcranial Magnetic Stimulation and Diffusion Tensor Imaging of Motor Tract Projections Correlate with the Different Domains of Hand Function.

OBJECTIVE: Schizencephaly is a rare congenital malformation that causes motor impairment. To determine the treatment strategy, each domain of the motor functions should be appropriately evaluated. We correlated a color map of diffusion tensor imaging (DTI) and transcranial magnetic stimulation (TMS) with the hand function test (HFT) to identify the type of hand function that each test (DTI and TMS) reflects. Further, we attempted to demonstrate the motor neuron organization in schizencephaly. METHOD: This retrospective study was conducted on 12 patients with schizencephaly. TMS was conducted in the first dorsal interosseous (FDI), biceps (BB), and deltoid muscles of the upper extremity, and contralateral MEP (cMEP) and ipsilateral MEP (iMEP) were recorded. The HFT included the grip strength, box and block (B&B), and 9-hole peg test. The schizencephalic cleft was confirmed using magnetic resonance imaging, and the corticospinal tract (CST) was identified using the color map of DTI. The symmetry indices for the peduncle and CST at pons level were calculated as the ratios of the cross-sectional area of the less-affected side and that of the more-affected side. RESULT: In the more-affected hemisphere TMS, no iMEP was obtained. In the less-affected hemisphere TMS, the iMEP response was detected in 9 patients and cMEP in all patients, which was similar to the pattern observed in unilateral lesion. Paretic hand grip strength was strongly correlated with the presence of iMEP (p = 0.044). The symmetry index of the color map of DTI was significantly correlated with the B&B (p = 0.008, R 2 = 0.416), whereas the symmetry index of the peduncle was not correlated with all HFTs. CONCLUSION: In patients with schizencephaly, the iMEP response rate is correlated with the hand function related to strength, while the symmetricity of the CST by the color map of DTI is correlated with the hand function associated with dexterity. Additionally, we suggest the possible motor organization pattern of schizencephaly following interhemispheric competition.

Acquisition of Developmental Milestones in Hypomyelination With Atrophy of the Basal Ganglia and Cerebellum and Other TUBB4A-Related Leukoencephalopathy.

Mutations in TUBB4A are associated with a spectrum of neurologic disorders categorized as TUBB4A-related leukoencephalopathy. Affected children can present with global developmental delay or normal early development, followed by a variable loss of skills over time. Further research is needed to characterize the factors associated with the divergent developmental trajectories in this rare monogenic disorder because this phenotypic spectrum is not fully explained by genotype alone.To characterize early psychomotor features, developmental milestones and age of disease onset were collected from medical records (n=54 individuals). Three subcohorts were identified: individuals with the common p.Asp249Asn variant vs all other genotypes with either early (<12 months of age) or late onset of presentation. Individuals with the p.Asp249Asn variant or those with non-p.Asp249Asn genotypes with later disease onset attained key milestones, including head control, sitting, and independent walking. Subjects with early-onset, non-p.Asp249Asn-associated disease were less likely to achieve developmental milestones. Next, we defined the developmental severity as the percentage of milestones attained by age 2 years. The mild form was defined as attaining at least 75% of key developmental milestones. Among cohort categorized as mild, individuals with p.Asp249Asn variant were more likely to lose acquired abilities when compared with non-p.Asp249Asn individuals.Our results suggest multiple influences on developmental trajectory, including a strong contribution from genotype and age of onset. Further studies are needed to identify additional factors that influence overall outcomes to better counsel families and to design clinical trials with appropriate clinical endpoints.

Further report of MEDS syndrome: Clinical and molecular delineation of a new Tunisian case.

Recently, an autosomal recessive disorder including the triad of microcephaly, infantile epileptic encephalopathy, and permanent neonatal diabetes syndrome (MEDS, OMIM#614231) has emerged as a new distinguishing syndrome. Eight cases of whom seven from Arab countries, have been reported in association with biallelic variants in the IER3IP1 gene (Immediate early response-3 interacting protein-1). Here, we describe a Tunisian boy who presented with permanent neonatal diabetes, microcephaly, generalized seizures and hypovirilized external genitalia consisting of a small genitalia and unilateral cryptorchidism. Chromosomal analysis indicated a 46, XY karyotype in all metaphases. Exome sequencing identified a homozygous missense variant (c.62 T > G; p. Val21Gly) in the IER3IP1 gene, that is predicted to alter the protein structure within the hydrophobic/transmembrane. This variant was previously reported in two cases associated with MEDS. This is the first reported case of MEDS in Tunisia. Our report focuses on the IER3IP1 related phenotypic spectrum and assumes abnormal genitalia as part of the syndrome. Consequently, we recommend to perform hormonal testing on this topic to understand the effect of the IER3IP1 variant on the male genital pathway.

Adult diagnosis of congenital serine biosynthesis defect: A treatable cause of progressive neuropathy.

A woman with ichthyosis, contractures, and progressive neuropathy represents the first case of phosphoserine aminotransferase deficiency diagnosed and treated in an adult. She has novel compound heterozygous mutations in the gene PSAT1. Treatment with high dose oral L-serine completely resolved the ichthyosis. Consideration of this diagnosis is important because early treatment with L-serine repletion can halt progression of neurodegeneration and potentially improve neurological disabilities. As exome sequencing becomes more widely implemented in the diagnostic evaluation of progressive neurodegenerative phenotypes, adult neurologists and geneticists will increasingly encounter later onset manifestations of inborn errors of metabolism classically considered in infancy and early childhood.

Characterization of ETFDH and PHGDH Mutations in a Patient with Mild Glutaric Aciduria Type II and Serine Deficiency.

Glutaric aciduria type II (GA-II) is a rare autosomal recessive disease caused by defects in electron transfer flavoprotein (ETF), ultimately causing insufficiencies in multiple acyl-CoA dehydrogenase (MAD). 3-phosphoglycerate dehydrogenase (3-PHGDH) deficiency, is another rare autosomal disorder that appears due to a defect in the synthesis of L-serine amino acid. Several mutations of ETFDH and PHGDH genes have been associated with different forms of GA-II and serine deficiency, respectively. In this study, we report a unique case of GA-II with serine deficiency using biochemical, genetic, and in silico approaches. The proband of Syrian descent had positive newborn screening (NBS) for GA-II. At two years of age, the patient presented with developmental regression, ataxia, and intractable seizures. Results of amino acid profiling demonstrated extremely low levels of serine. Confirmatory tests for GA-II and whole exome sequencing (WES) were performed to determine the etiology of intractable seizure. Sequencing results indicated a previously reported homozygous missense mutation, c.679 C>A (p.Pro227Thr) in the ETFDH gene and a novel missense homozygous mutation c.1219 T>C (p.Ser407Pro) in the PHGDH gene. In silico tools predicted these mutations as deleterious. Here, the clinical and biochemical investigations indicate that ETFDH:p.Pro227Thr and PHGDH:p.Ser407Pro variants likely underlie the pathogenesis of GA-II and serine deficiency, respectively. This study indicates that two rare autosomal recessive disorders should be considered in consanguineous families, more specifically in those with atypical presentation.

Expanding the genotypic spectrum of PYCR2 and a common ancestry in Thai patients with hypomyelinating leukodystrophy 10.

PYCR2 pathogenic variants lead to an autosomal recessive hypomyelinating leukodystrophy 10 (HLD10), characterized by global developmental delay, microcephaly, facial dysmorphism, movement disorder, and hypomyelination. This study identified the first two unrelated Thai patients with HLD10. Patient 1 harbored the novel compound heterozygous variants, c.257T>G (p.Val86Gly) and c.400G>A (p.Val134Met), whereas patient 2 possessed the homozygous variant, c.400G>A (p.Val134Met), in PYCR2. Haplotype analysis revealed that the two families' members shared a 2.3 Mb region covering the c.400G>A variant, indicating a common ancestry. The variant was estimated to age 1450 years ago. Since the c.400G>A was detected in three out of four mutant alleles and with a common ancestry, this variant might be common in Thai patients. We also reviewed the phenotype and genotype of all 35 previously reported PYCR2 patients and found that majorities of cases were homozygous with a consanguineous family history, except patient 1 and another reported case who were compound heterozygous. All patients had microcephaly and developmental delay. Hypotonia and peripheral spasticity were common. Hypomyelination or delayed myelination was a typical radiographic feature. Here, we report the first two Thai patients with HLD10 with the novel PYCR2 variants expanding the genotypic spectrum and suggest that the c.400G>A might be a common mutation in Thai patients.

Molecular and metabolic bases of tetrahydrobiopterin (BH4) deficiencies.

Tetrahydrobiopterin (BH4) deficiency is caused by genetic variants in the three genes involved in de novo cofactor biosynthesis, GTP cyclohydrolase I (GTPCH/GCH1), 6-pyruvoyl-tetrahydropterin synthase (PTPS/PTS), sepiapterin reductase (SR/SPR), and the two genes involved in cofactor recycling, carbinolamine-4α-dehydratase (PCD/PCBD1) and dihydropteridine reductase (DHPR/QDPR). Dysfunction in BH4 metabolism leads to reduced cofactor levels and may result in systemic hyperphenylalaninemia and/or neurological sequelae due to secondary deficiency in monoamine neurotransmitters in the central nervous system. More than 1100 patients with BH4 deficiency and 800 different allelic variants distributed throughout the individual genes are tabulated in database of pediatric neurotransmitter disorders PNDdb. Here we provide an update on the molecular-genetic analysis and structural considerations of these variants, including the clinical courses of the genotypes. From a total of 324 alleles, 11 are associated with the autosomal recessive form of GTPCH deficiency presenting with hyperphenylalaninemia (HPA) and neurotransmitter deficiency, 295 GCH1 variant alleles are detected in the dominant form of L-dopa-responsive dystonia (DRD or Segawa disease) while phenotypes of 18 alleles remained undefined. Autosomal recessive variants observed in the PTS (199 variants), PCBD1 (32 variants), and QDPR (141 variants) genes lead to HPA concomitant with central monoamine neurotransmitter deficiency, while SPR deficiency (104 variants) presents without hyperphenylalaninemia. The clinical impact of reported variants is essential for genetic counseling and important for development of precision medicine.

Fumarase Deficiency: A Case With a New Pathogenic Mutation and a Review of the Literature.

Fumarase deficiency (FD) is a rare and severe autosomal disorder, caused by inactivity of the enzyme fumarase, due to biallelic mutations of the fumarase hydratase (FH) gene. Several pathogenic mutations have been published. The article describes an infant with failure to thrive, microcephaly, axial hypotonia, and developmental retardation with increased excretion of fumarate, no activity of fumarase and a homozygous mutation of the FH gene, which was until recently only known as a variant of unknown significance. Carriers of pathogenic mutations in the FH gene are at risk for developing renal cell carcinoma and should therefore be screened. Both parents were healthy carriers of the mutation and had decreased levels of enzyme activity. In addition, the article presents an overview and analysis of all cases of FD reported thus far in the literature.

TRAPγ-CDG shows asymmetric glycosylation and an effect on processing of proteins required in higher organisms.

Newly synthesised glycoproteins enter the rough endoplasmic reticulum through a translocation pore. The translocon associated protein (TRAP) complex is located close to the pore. In a patient with a homozygous start codon variant in TRAPγ (SSR3), absence of TRAPγ causes disruption of the TRAP complex, impairs protein translocation into the endoplasmic reticulum and affects transport, for example, into the brush-border membrane. Furthermore, we observed an unbalanced non-occupancy of N-glycosylation sites. The major clinical features are intrauterine growth retardation, facial dysmorphism, congenital diarrhoea, failure to thrive, pulmonary disease and severe psychomotor disability.

HIV-1 Tat Dysregulates the Hypothalamic-Pituitary-Adrenal Stress Axis and Potentiates Oxycodone-Mediated Psychomotor and Anxiety-Like Behavior of Male Mice.

Human immunodeficiency virus (HIV) is associated with co-morbid affective and stress-sensitive neuropsychiatric disorders that may be related to dysfunction of the hypothalamic-pituitary-adrenal (HPA) stress axis. The HPA axis is perturbed in up to 46% of HIV patients, but the mechanisms are not known. The neurotoxic HIV-1 regulatory protein, trans-activator of transcription (Tat), may contribute. We hypothesized that HPA dysregulation may contribute to Tat-mediated interactions with oxycodone, a clinically-used opioid often prescribed to HIV patients. In transgenic male mice, Tat expression produced significantly higher basal corticosterone levels with adrenal insufficiency in response to a natural stressor or pharmacological blockade of HPA feedback, recapitulating the clinical phenotype. On acute exposure, HIV-1 Tat interacted with oxycodone to potentiate psychomotor and anxiety like-behavior in an open field and light-dark transition tasks, whereas repeated exposure sensitized stress-related psychomotor behavior and the HPA stress response. Pharmacological blockade of glucocorticoid receptors (GR) partially-restored the stress response and decreased oxycodone-mediated psychomotor behavior in Tat-expressing mice, implicating GR in these effects. Blocking corticotrophin-releasing factor (CRF) receptors reduced anxiety-like behavior in mice that were exposed to oxycodone. Together, these effects support the notion that Tat exposure can dysregulate the HPA axis, potentially raising vulnerability to stress-related substance use and affective disorders.

ANO3 and early-onset dyskinetic encephalopathy.

Mutations in the ANO3 gene have been associated with autosomal dominant craniocervical dystonia. However, little else is known about the genotype-phenotype characteristics of this disorder. Here we describe a 3 years-old girl with distal myoclonic dystonia. Whole exome sequencing in trio revealed a de novo missense ANO3 variant not previously described in international databases. A global psychomotor regression was observed once dystonia was present. Brain MRI changes paralleled these findings: whereas MRI at the age of 18 months was normal, mild brain and cerebellar atrophy was observed 18 months later. These results suggest that missense mutations in ANO3 may underlie complex disorders particularly characterized by early psychomotor regression and dystonia.

The first familial case of inherited intellectual developmental disorder with dysmorphic facies and behavioral abnormalities (IDDFBA) with a novel FBXO11 variant.

Intellectual developmental disorder with dysmorphic facies and behavioral abnormalities (IDDFBA) caused by germline de novo variants in FBXO11 was recently recognized as a novel intellectual disability (ID) syndrome through reverse phenotyping after whole-exome sequencing (WES). Fewer than 50 disease-causing de novo FBXO11 variants in IDDFBA are reported thus far. Here, we present the first report of a family showing autosomal dominantly inherited IDDFBA, harboring a novel heterozygous variant in FBXO11 (c.2401_2405dup;p. Gly803Leufs*6) identified by WES. In this family, the mother and two daughters showed mild ID and mild facial dysmorphism. This finding is expected to increase our understanding of the genotype-phenotype of IDDFBA and to facilitate genetic counseling for the disorder caused by FBXO11.

A new homozygous HERC1 gain-of-function variant in MDFPMR syndrome leads to mTORC1 hyperactivation and reduced autophagy during cell catabolism.

The giant 532 kDa HERC1 protein is a ubiquitin ligase that interacts with tuberous sclerosis complex subunit 2 (TSC2), a negative upstream regulator of the mammalian target of rapamycin complex 1 (mTORC1). TSC2 regulates anabolic cell growth through its influence on protein synthesis, cell growth, proliferation, autophagy, and differentiation. TSC subunit 1 (TSC1) stabilizes TSC2 by inhibiting the interaction between TSC2 and HERC1, forming a TSC1-TSC2 complex that negatively regulates mTORC1. HERC1-TSC2 interaction destabilizes and degrades TSC2. Recessive mutations in HERC1 have been reported in patients with intellectual disability. Some patients exhibit epilepsy, macrocephaly, somatic overgrowth, and dysmorphic facial features as well. Here we describe two sisters from a consanguineous marriage with a novel homozygous missense variant in the C-terminal HECT domain of HERC1 [chr15:g63,907,989C>G GRCh37.p11 | c.14,072G>C NM_003922 | p.(Arg4,691Pro)]. Symptoms compris global developmental delay, macrocephaly, somatic overgrowth, intellectual disability, seizures, schizoaffective disorder, and pyramidal tract signs. We functionally assessed the HERC1 mutation by investigation of patient and control fibroblasts under normal and nutrient starving conditions. During catabolic state, mTORC1 activity remained high in patient fibroblasts, which stands in stark contrast to its downregulation in controls. This was corroborated by an abnormally high phosphorylation of S6K1-kinase, a direct downstream target of mTORC1, in patients. Moreover, autophagy, usually enhanced in catabolic states, was down-regulated in patient fibroblasts. These data confirm that the missense variant found in both patients results in a gain-of-function for the mutant HERC1 protein.

Evidence of the milder phenotypic spectrum of c.1582G>A PIGT variant: Delineation based on seven novel Polish patients.

PIGT is one of over 29 glycosylphosphatidylinositol biosynthesis defect genes. Mutations cause genetically determined disorders characterized mainly by epilepsy with fever-sensitivity, central hypotonia, psychomotor delay and congenital malformations. The disease is known as multiple congenital anomalies-hypotonia-seizures syndrome 3 (MCAHS3) or glycosylphosphatidylinositol biosynthesis defect-7. Twenty-eight cases have been reported until today. We present seven novel Polish patients, all harboring 1582G>A variant in a homozygous or compound heterozygous state which seems to cause a milder phenotype of the disease.

A homozygous truncating NALCN variant in two Afro-Caribbean siblings with hypotonia and dolichocephaly.

NALCN encodes a sodium ion leak channel expressed in the nervous system that conducts a persistent influx of sodium ions to facilitate action potential formation. Homozygous or compound heterozygous loss of function variants in NALCN cause infantile hypotonia with psychomotor retardation and characteristic facies-1 (IHPRF1; OMIM 615419). Through exome and Sanger sequencing, we found two siblings of Afro-Caribbean ancestry who are homozygous for a known NALCN pathogenic variant, p.Arg735Ter, leading to failure to thrive, severe hypotonia, and dolichocephaly. The older sibling died suddenly without a known etiology after evaluation but before molecular diagnosis. An international collaboration originating from a resource limited Caribbean island facilitated molecular diagnosis. Due to its small population, geographical isolation, and low socioeconomic status, the island lacks many specialty medical services, including clinical genetics. Descriptions of genetic disorders affecting individuals of Afro-Caribbean ancestry are rarely reported in the medical literature. Diagnosis of IHPRF1 is important, as individuals with biallelic pathogenic NALCN variants are severely affected and potentially are at risk for cardiorespiratory arrest. Additionally, knowing the pathogenic variants allows the possibility of prenatal or preimplantation genetic diagnosis.

Combined HIV-1 Tat and oxycodone activate the hypothalamic-pituitary-adrenal and -gonadal axes and promote psychomotor, affective, and cognitive dysfunction in female mice.

The majority of HIV+ patients present with neuroendocrine dysfunction and ~50% experience co-morbid neurological symptoms including motor, affective, and cognitive dysfunction, collectively termed neuroHIV. In preclinical models, the neurotoxic HIV-1 regulatory protein, trans-activator of transcription (Tat), promotes neuroHIV pathology that can be exacerbated by opioids. We and others find gonadal steroids, estradiol (E2) or progesterone (P4), to rescue Tat-mediated pathology. However, the combined effects of Tat and opioids on neuroendocrine function and the subsequent ameliorative capacity of gonadal steroids are unknown. We found that conditional HIV-1 Tat expression in naturally-cycling transgenic mice dose-dependently potentiated oxycodone-mediated psychomotor behavior. Tat increased depression-like behavior in a tail-suspension test among proestrous mice, but decreased it among diestrous mice (who already demonstrated greater depression-like behavior); oxycodone reversed these effects. Combined Tat and oxycodone produced apparent behavioral disinhibition of anxiety-like responding which was greater on diestrus than on proestrus. These mice made more central entries in an open field, but spent less time there and demonstrated greater circulating corticosterone. Tat increased the E2:P4 ratio of circulating steroids on diestrus and acute oxycodone attenuated this effect, but repeated oxycodone exacerbated it. Corticotropin-releasing factor was increased by Tat expression, acute oxycodone exposure, and was greater on diestrus compared to proestrus. In human neuroblastoma cells, Tat exerted neurotoxicity that was ameliorated by E2 (1 or 10 nM) or P4 (100, but not 10 nM) independent of oxycodone. Oxycodone decreased gene expression of estrogen and κ-opioid receptors. Thus, neuroendocrine function may be an important target for HIV-1 Tat/opioid interactions.

Structural network changes in cerebral small vessel disease.

OBJECTIVES: To investigate whether longitudinal structural network efficiency is associated with cognitive decline and whether baseline network efficiency predicts mortality in cerebral small vessel disease (SVD). METHODS: A prospective, single-centre cohort consisting of 277 non-demented individuals with SVD was conducted. In 2011 and 2015, all participants were scanned with MRI and underwent neuropsychological assessment. We computed network properties using graph theory from probabilistic tractography and calculated changes in psychomotor speed and overall cognitive index. Multiple linear regressions were performed, while adjusting for potential confounders. We divided the group into mild-to-moderate white matter hyperintensities (WMH) and severe WMH group based on median split on WMH volume. RESULTS: The decline in global efficiency was significantly associated with a decline in psychomotor speed in the group with severe WMH (ß=0.18, p=0.03) and a trend with change in cognitive index (ß=0.14, p=0.068), which diminished after adjusting for imaging markers for SVD. Baseline global efficiency was associated with all-cause mortality (HR per decrease of 1 SD 0.43, 95% CI 0.23 to 0.80, p=0.008, C-statistic 0.76). CONCLUSION: Disruption of the network efficiency, a metric assessing the efficiency of network information transfer, plays an important role in explaining cognitive decline in SVD, which was however not independent of imaging markers of SVD. Furthermore, baseline network efficiency predicts risk of mortality in SVD that may reflect the global health status of the brain in SVD. This emphasises the importance of structural network analysis in the context of SVD research and the use of network measures as surrogate markers in research setting.

Functional expression of CLIFAHDD and IHPRF pathogenic variants of the NALCN channel in neuronal cells reveals both gain- and loss-of-function properties.

The excitability of neurons is tightly dependent on their ion channel repertoire. Among these channels, the leak sodium channel NALCN plays a crucial role in the maintenance of the resting membrane potential. Importantly, NALCN mutations lead to complex neurodevelopmental syndromes, including infantile hypotonia with psychomotor retardation and characteristic facies (IHPRF) and congenital contractures of limbs and face, hypotonia and developmental delay (CLIFAHDD), which are recessively and dominantly inherited, respectively. Unfortunately, the biophysical properties of NALCN are still largely unknown to date, as well as the functional consequences of both IHPRF and CLIFAHDD mutations on NALCN current. Here we have set-up the heterologous expression of NALCN in the neuronal cell line NG108-15 to investigate the electrophysiological properties of NALCN carrying representative IHPRF and CLIFAHDD mutations. Several original properties of the wild-type (wt) NALCN current were retrieved: mainly carried by external Na+, blocked by Gd3+, insensitive to TTX and potentiated by low external Ca2+ concentration. However, we found that this current displays a time-dependent inactivation in the -80/-40 mV range of membrane potential, and a non linear current-voltage relationship indicative of voltage sensitivity. Importantly, no detectable current was recorded with the IHPRF missense mutation p.Trp1287Leu (W1287L), while the CLIFAHDD mutants, p.Leu509Ser (L509S) and p.Tyr578Ser (Y578S), showed higher current densities and slower inactivation, compared to wt NALCN current. This study reveals that heterologous expression of NALCN channel can be achieved in the neuronal cell line NG108-15 to study the electrophysiological properties of wt and mutants. From our results, we conclude that IHPRF and CLIFAHDD missense mutations are loss- and gain-of-function variants, respectively.