Novel genetic causes for cerebral visual impairment

Genetic Structure and Selection Signals for Extreme Environment Adaptation in Lop Sheep of Xinjiang

OBJECTIVE

Lop sheep species exhibit remarkable adaptability to desert pastures and extreme arid climates, demonstrating tolerance to rough feeding and high resistance to stress. However, little is known about the population genetic diversity of Lop sheep and the genetic mechanisms underlying their adaptability to extreme environments.

METHODS

Blood samples were collected from a total of 110 individuals comprising 80 Ruoqiang Lop sheep and 30 Yuli Lop sheep. A total of 110 Lop sheep were subjected to whole genome resequencing to analyze genetic diversity, population structure, and signatures of selection in both regions.

RESULTS

The genetic diversity of the Lop sheep population is substantial, and the degree of inbreeding is low. In comparison to the Lop sheep in Yuli County, the genetic diversity and linkage disequilibrium analysis results for the Lop sheep population in Ruoqiang County are slightly lower. Population structure analysis indicates that Ruoqiang and Yuli Lop sheep have differentiated into two independent groups. Using Yuli Lop sheep as the reference group, an analysis of the extreme environmental adaptability selection signal of Lop sheep was conducted. The FST and π ratio under the 1% threshold identified 1686 and 863 candidate genes, respectively, with their intersection yielding a total of 122 candidate genes. Functional annotation revealed that these genes are associated with various traits, including immune response (SLC12A2, FOXP1, PANX1, DYNLRB2, RAP1B, and SEMA4D), heat and cold resistance (DNAJC13, PLCB1, HIKESHI, and PITPNC1), desert adaptation (F13A1, PANX1, ST6GAL1, STXBP3, ACTN4, and ATP6V1A), and reproductive performance (RAP1B, RAB6A, PLCB1, and METTL15).

CONCLUSIONS

These research findings provide a theoretical foundation for understanding the survival and reproductive characteristics of Lop sheep in extreme environments, and they hold practical value for the conservation and utilization of Lop sheep genetic resources, as well as for genetic improvement efforts.

A school-based intervention to improve mental health outcomes for children with cerebral visual impairment (CVI): feasibility cluster randomised trial

BACKGROUND

Cerebral visual impairment (CVI) refers to brain-related vision difficulties, which are often undiagnosed and may lead to poor mental health outcomes. We have developed an intervention to improve mental health outcomes for affected children, and it requires evaluation. The aim of this study was to assess the feasibility of methods proposed for a future definitive cluster randomised trial.

METHODS

This 18-month study took place in South West England, UK, between 2019 and 2021 including a 6-month pause due to the COVID pandemic. Participants were children aged 7-10 years in mainstream primary schools and their teachers and parents. We recruited head teachers on behalf of their school. The intervention was a resource pack for teachers explaining about CVI, providing universal and targeted strategies to help children with CVI and the offer of CVI assessments at the local eye clinic. The control schools continued with usual practice. Our objectives were to evaluate the feasibility of recruitment and data collection, attrition, acceptability of the study methods and implementation of the intervention. We conducted a process evaluation including interviews and questionnaires.

RESULTS

We sent invitation letters to 297 schools, received responses to 6% and recruited 40% of these (7 schools, 1015 children). Parents of 36/1015 (3.5%) children opted out. Baseline data were collected from teachers for 94% children, and 91% children completed self-report questionnaires; parent-report questionnaires were returned for 19% of children. During the exceptional circumstance of the COVID pandemic, two schools left the study, and many children were not attending school, meaning follow-up data were received from 32% of children, 16% of teachers and 14% of parents. Interview data indicated that the intervention was acceptable, and teachers would have preferred on-site eye tests to the offer of a clinic appointment and a clear timetable for study events. Teachers in intervention schools reported expected changes in the children's and their own behaviour. There was some contamination between study arms.

CONCLUSIONS

A full-scale trial would be feasible, enhanced by insights from this feasibility trial, in non-pandemic times. Sharing these data with teachers, education policymakers and parents is planned to refine the design.

TRIAL REGISTRATION

ISRCTN13762177.

Adaptive functioning and relationship to visual behavior in children with cerebral/cortical visual impairment

BACKGROUND

Cerebral/cortical visual impairment (CVI) is a leading cause of pediatric visual impairment in developed countries and is associated with neurologic conditions that may impair adaptive functioning or skills required to perform everyday tasks (eg, communication, socialization, and daily living skills). Adaptive behavior in children with CVI has not been systematically studied, and the relationship between visual function and adaptive function in CVI is unknown.

METHODS

We prospectively recruited 49 children with CVI (mean age, 4 ± 3 years). Adaptive behavior was evaluated using the Vineland Adaptive Behavior Scale, 3rd edition (VABS-III). Visual acuity was assessed by a pediatric neuro-ophthalmologist using the six-level Visual Behavior Scale (VBS). The relationship between VBS and VABS-III scores was assessed using a Spearman correlation coefficient and a multiple regression model to correct for age, sex, and neurologic and ophthalmologic comorbidities.

RESULTS

In our cohort, mean adaptive behavior scores in children with CVI were below the 1st percentile on all VABS-III domains and subdomains. Visual acuity, as assessed by VBS, was significantly associated with VABS-III total adaptive behavior composite score (P = 0.04), socialization (P = 0.03) domain, and interpersonal (P = 0.04), play and leisure (P = 0.04), and personal (P = 0.01) subdomains.

CONCLUSIONS

Children with CVI have significantly reduced adaptive functioning. Visual behavior is correlated with socialization and some daily living skills. Future longitudinal studies should evaluate whether adaptive functioning increases as visual acuity improves in children with CVI, which may have prognostic implications.

Extended range proteomic analysis of blood plasma from schizophrenia patients

Introduction

The high prevalence of schizophrenia worldwide makes it necessary to proceed from subjective assessment of patient's clinical symptoms in diagnosis making to searching for circulating blood biomarkers. On the one hand, searching for molecular markers and targets for therapeutics will make it possible to refine and detail the molecular mechanisms of pathology development, while on the other hand, it will offer new opportunities for elaborating novel approaches to disease diagnosis and enhance efficacy and timeliness of drug therapy.

Methods

In this study, we performed an extended-range proteomic analysis of plasma samples collected from 48 study subjects with confirmed diagnosis of schizophrenia and 50 healthy volunteers. The high-resolution tandem mass spectra recorded in the data-dependent acquisition mode were analyzed using the MaxQuant algorithm for the library of known protein sequences and the PowerNovo algorithm for de novo protein sequencing.

Results

It was demonstrated that both strategies show similar results for high-abundance proteins (≥1 μg/mL). For mid-abundance (10 ng/mL - 1 μg/mL) and low-abundance (<10 ng/mL) proteins, the results obtained by the two search strategies complement each other.

Discussion

Group-specific proteins for the samples of schizophrenia patients were identified, presumably being involved in synaptic plasticity, angiogenesis, transcriptional regulation, protein stabilization and degradation.

Expression and clinical significance of U2AF homology motif kinase 1 in oral squamous cell carcinoma

OBJECTIVE

U2AF homology motif kinase 1 (UHMK1) is a newly discovered molecule that may have multiple functions. Recent studies have revealed that UHMK1 had aberrant expression in many tumors and was associated with tumor progression. However, UHMK1 was rarely reported in oral squamous cell carcinoma (OSCC).

STUDY DESIGN

In this study, Western blot, quantitative real-time polymerase chain reaction (PCR), and immunohistochemistry were used to detect the expression of UHMK1 in OSCC and peritumoral non-neoplastic tissues. Then, its relationship with clinicopathologic parameters was analyzed. The Kaplan-Meier method and Cox regression model were used to analyze the effects of UHMK1 expression on the prognosis and survival of OSCC patients.

RESULTS

Our results showed that UHMK1 had higher expression in OSCC tissues compared with in peritumoral non-neoplastic tissues, and its high expression was associated with high TNM stage and lymph node metastasis. High UHMK1 expression was related to short overall and disease-free survival times. Moreover, UHMK1 expression was identified as an independent prognostic factor that influences overall and disease-free survival of OSCC patients.

CONCLUSIONS

High expression of UHMK1 is associated with the poor prognosis of patients, and it can be used as a potential prognostic molecule for OSCC.

De novo AHDC1 Deletions Identified by Genome Sequencing in Two Individuals with Xia-Gibbs Syndrome

Introduction

Xia-Gibbs syndrome (XGS) is a rare syndromic disorder characterized by developmental delay with intellectual disability, muscular hypotonia, brain anomalies, and nonspecific dysmorphic features. Different heterozygous variants in AHDC1 have been reported as causal for XGS, comprising mainly de novo stop-gain and frameshift events, but also missense variants, deletions, and a duplication of the locus.

Case Presentation

We hereby report 2 patients with clinical features of XGS. In the first patient, a de novo interstitial deletion in 1p36.11p35.3 encompassing the entire coding region of AHDC1 was initially suspected by trio exome sequencing and subsequently confirmed by shallow genome sequencing. In the second patient, a de novo deletion comprising most of the 5' untranslated region of AHDC1 was detected by genome sequencing.

Conclusion

We identified the smallest deletion comprising AHDC1 reported so far by shallow genome sequencing as well as another small AHDC1 deletion by genome sequencing. These methods represent useful techniques for the identification and confirmation of small deletions and structural variants. Furthermore, our data provide additional evidence of AHDC1 haploinsufficiency as a disease mechanism in XGS. Clinically, foot deformity, skin and connective tissue abnormalities observed in one of the patients are consistent with other reported cases of XGS. These findings suggest that these manifestations could be considered as more prevalent characteristics, underscoring the importance of in-depth phenotyping.

Expanding the Spectrum of Autosomal Dominant ATP6V1A-Related Disease: Case Report and Literature Review

BACKGROUND

Developmental and epileptic encephalopathies (DEE) are a group of disorders often linked to de novo mutations, including those in the ATP6V1A gene. These mutations, particularly dominant gain-of-function (GOF) variants, have been associated with a spectrum of phenotypes, ranging from severe DEE and infantile spasms to milder conditions like autism spectrum disorder and language delays.

METHODS

We aim to expand ATP6V1A-related disease spectrum by describing a six-year-old boy who presented with a febrile seizure, mild intellectual disability (ID), language delay, acquired microcephaly, and dysmorphic features.

RESULTS

Genetic analysis revealed a novel de novo heterozygous pathogenic variant (c.82G>A, p.Val28Met) in the ATP6V1A gene. He did not develop epilepsy, and neuroimaging remained normal over five years of follow-up. Although ATP6V1A mutations have traditionally been linked to severe neurodevelopmental disorders, often with early-onset epilepsy, they may exhibit milder, non-progressive phenotypes, challenging previous assumptions about the severity of ATP6V1A-related conditions.

CONCLUSIONS

This case expands the known clinical spectrum, illustrating that not all patients with ATP6V1A mutations exhibit severe neurological impairment or epilepsy and underscoring the importance of including this gene in differential diagnoses for developmental delays, especially when febrile seizures or dysmorphic features are present. Broader genotype-phenotype correlations are essential for improving predictive accuracy and guiding clinical management, especially as more cases with mild presentations are identified.

De novo variants in GABRA4 are associated with a neurological phenotype including developmental delay, behavioral abnormalities and epilepsy

Nine out of 19 genes encoding GABAA receptor subunits have been linked to monogenic syndromes characterized by seizures and developmental disorders. Previously, we reported the de novo variant p.(Thr300Ile) in GABRA4 in a patient with epilepsy and neurodevelopmental abnormalities. However, no new cases have been reported since then. Through an international collaboration, we collected molecular and phenotype data of individuals carrying de novo variants in GABRA4. Patients and their parents were investigated either by exome or genome sequencing, followed by targeted Sanger sequencing in some cases. All variants within the transmembrane domain, including the previously reported p.(Thr300Ile) variant, were characterized in silico and analyzed by molecular dynamics (MD) simulation studies. We identified three novel de novo missense variants in GABRA4 (NM_000809.4): c.797 C > T, p.(Pro266Leu), c.899 C > A, p.(Thr300Asn), and c.634 G > A, p.(Val212Ile). The p.(Thr300Asn) variant impacts the same codon as the previously reported variant p.(Thr300Ile) and likely arose post-zygotically as evidenced by sequencing oral mucosal cells. Overlapping phenotypes among affected individuals included developmental delay (4/4), epileptiform EEG abnormalities (3/4), attention deficits (3/4), seizures (2/4), autistic features (2/4) and structural brain abnormalities (2/4). MD simulations of the three variants within the transmembrane domain of the receptor indicate that sub-microsecond scale dynamics differ between wild-type and mutated subunits. Taken together, our findings further corroborate an association between GABRA4 and a neurological phenotype including variable neurodevelopmental, behavioral and epileptic abnormalities.

Genetic network analysis indicate that individuals affected by neurodevelopmental conditions have genetic variations associated with ophthalmologic alterations: A critical review of literature

Changes in the nervous system are related to a wide range of mental disorders, which include neurodevelopmental disorders (NDD) that are characterized by early onset mental conditions, such as schizophrenia and autism spectrum disorders and correlated conditions (ASD). Previous studies have shown distinct genetic components associated with diverse schizophrenia and ASD phenotypes, with mostly focused on rescuing neural phenotypes and brain activity, but alterations related to vision are overlooked. Thus, as the vision is composed by the eyes that itself represents a part of the brain, with the retina being formed by neurons and cells originating from the glia, genetic variations affecting the brain can also affect the vision. Here, we performed a critical systematic literature review to screen for all genetic variations in individuals presenting NDD with reported alterations in vision. Using these restricting criteria, we found 20 genes with distinct types of genetic variations, inherited or de novo, that includes SNP, SNV, deletion, insertion, duplication or indel. The variations occurring within protein coding regions have different impact on protein formation, such as missense, nonsense or frameshift. Moreover, a molecular analysis of the 20 genes found revealed that 17 shared a common protein-protein or genetic interaction network. Moreover, gene expression analysis in samples from the brain and other tissues indicates that 18 of the genes found are highly expressed in the brain and retina, indicating their potential role in adult vision phenotype. Finally, we only found 3 genes from our study described in standard public databanks of ophthalmogenetics, suggesting that the other 17 genes could be novel target for vision diseases.

Cerebral visual impairment: genetic diagnoses and phenotypic associations

BACKGROUND

Cerebral visual impairment (CVI) is the most common form of paediatric visual impairment in developed countries. CVI can arise from a host of genetic or acquired causes, but there has been limited research to date on CVI in the context of genetic disorders.

METHODS

We carried out a retrospective analysis of genotypic and phenotypic data for participants with CVI within the DECIPHER database and 100 000 Genomes Project (100KGP).

RESULTS

158 individuals with CVI were identified across both cohorts. Within this group, pathogenic or likely pathogenic sequence variants in 173 genes were identified. 25 of these genes already have known associations with CVI, while the remaining 148 are candidate genes for this phenotype. Gene ontology analysis of the CVI gene sets from both DECIPHER and 100KGP suggests that CVI has a similar degree of genetic heterogeneity to other neurodevelopmental phenotypes, and a strong association with genetic variants converging on ion channels and receptor functions. Individuals with a monogenic disorder and CVI have a higher frequency of epilepsies and severe neurodisability than individuals with a monogenic disorder but not CVI.

CONCLUSION

This study supports the availability of genetic testing for individuals with CVI alongside other neurodevelopmental difficulties. It also supports the availability of ophthalmological screening for individuals with genetic diagnoses linked to CVI. Further studies could elaborate on the links between specific genetic disorders, visual maturation and broader neurodevelopmental characteristics.

Functional prediction of the potential NGLY1 mutations associated with rare disease CDG

Genetic diseases are currently diagnosed by functional mutations. However, only some mutations are associated with disease. It is necessary to establish a quick prediction model for clinical screening. Pathogenic mutations in NGLY1 cause a rare autosomal recessive disease known as congenital disorder of deglycosylation (NGLY1-CDDG). Although NGLY1-CDDG can be diagnosed through gene sequencing, clinical relevance of a detected mutation in NGLY1 needs to be further confirmed. In this study, taken NGLY1-CDDG as an example, a comprehensive and practical predictive model for pathogenic mutations on NGLY1 through an NGLY1/Glycopeptide complex model was constructed, the binding sites of NGLY1 and glycopeptides were simulated, and an in vitro enzymatic assay system was established to facilitate quick clinical decisions for NGLY1-CDDG patients. The docking model covers 42 % of reported NGLY1-CDDG missense mutations (5/12). All reported mutations were subjected to in vitro enzymatic assay in which 18 mutations were dysfunctional (18/30). In addition, a full spectrum of functional R328 mutations was assayed and 11 mutations were dysfunctional (11/19). In this study, a model of NGLY1 and glycopeptides was built for potential functional mutations in NGLY1. In addition, the effect of potential regulatory compounds, including N-acetyl-l-cysteine and dithiothreitol, on NGLY1 was examined. The established in vitro assay may serve as a standard protocol to facilitate rapid diagnosis of all mutations in NGLY1-CDDG. This method could also be applied as a comprehensive and practical predictive model for the other rare genetic diseases.

Developmental epileptic encephalopathy in DLG4-related synaptopathy

OBJECTIVE

The postsynaptic density protein of excitatory neurons PSD-95 is encoded by discs large MAGUK scaffold protein 4 (DLG4), de novo pathogenic variants of which lead to DLG4-related synaptopathy. The major clinical features are developmental delay, intellectual disability (ID), hypotonia, sleep disturbances, movement disorders, and epilepsy. Even though epilepsy is present in 50% of the individuals, it has not been investigated in detail. We describe here the phenotypic spectrum of epilepsy and associated comorbidities in patients with DLG4-related synaptopathy.

METHODS

We included 35 individuals with a DLG4 variant and epilepsy as part of a multicenter study. The DLG4 variants were detected by the referring laboratories. The degree of ID, hypotonia, developmental delay, and motor disturbances were evaluated by the referring clinician. Data on awake and sleep electroencephalography (EEG) and/or video-polygraphy and brain magnetic resonance imaging were collected. Antiseizure medication response was retrospectively assessed by the referring clinician.

RESULTS

A large variety of seizure types was reported, although focal seizures were the most common. Encephalopathy related to status epilepticus during slow-wave sleep (ESES)/developmental epileptic encephalopathy with spike-wave activation during sleep (DEE-SWAS) was diagnosed in >25% of the individuals. All but one individual presented with neurodevelopmental delay. Regression in verbal and/or motor domains was observed in all individuals who suffered from ESES/DEE-SWAS, as well as some who did not. We could not identify a clear genotype-phenotype relationship even between individuals with the same DLG4 variants.

SIGNIFICANCE

Our study shows that a subgroup of individuals with DLG4-related synaptopathy have DEE, and approximately one fourth of them have ESES/DEE-SWAS. Our study confirms DEE as part of the DLG4-related phenotypic spectrum. Occurrence of ESES/DEE-SWAS in DLG4-related synaptopathy requires proper investigation with sleep EEG.

Functional difficulty among young children in Bangladesh: An analysis of nationally representative data

Functional difficulty in children is a crucial public health problem still undervalued in developing countries. This study explored the socio-demographic factors and anthropometry associated with children's functional difficulty in Bangladesh. Data for 2-4-year-old children, obtained from Multiple Indicator Cluster Survey 2019, were used in this study. The mixed-effects logistic regression model was used to analyse the data. Children whose mothers had functional difficulty were found to be 2.75 times more likely to have functional difficulty than children whose mothers had no functional difficulty (95% CI 1.63-4.63). Male children were more likely to experience functional difficulty than female children (OR = 1.48). Furthermore, stunting was found to be significantly associated with functional difficulty (OR = 1.50). The study also revealed that division and mother's education, specifically, children with mothers having higher secondary + education, had significant association with the outcome variable. The findings provided a vital overview of child disability in a developing country.

KCTD10 regulates brain development by destabilizing brain disorder-associated protein KCTD13

KCTD10 belongs to the KCTD (potassiumchannel tetramerization domain) family, many members of which are associated with neuropsychiatric disorders. However, the biological function underlying the association with brain disorders remains to be explored. Here, we reveal that Kctd10 is highly expressed in neuronal progenitors and layer V neurons throughout brain development. Kctd10 deficiency triggers abnormal proliferation and differentiation of neuronal progenitors, reduced deep-layer (especially layer V) neurons, increased upper-layer neurons, and lowered brain size. Mechanistically, we screened and identified a unique KCTD10-interacting protein, KCTD13, associated with neurodevelopmental disorders. KCTD10 mediated the ubiquitination-dependent degradation of KCTD13 and KCTD10 ablation resulted in a considerable increase of KCTD13 expression in the developing cortex. KCTD13 overexpression in neuronal progenitors led to reduced proliferation and abnormal cell distribution, mirroring KCTD10 deficiency. Notably, mice with brain-specific Kctd10 knockout exhibited obvious motor deficits. This study uncovers the physiological function of KCTD10 and provides unique insights into the pathogenesis of neurodevelopmental disorders.

A novel DLG4 variant causes DLG4-related synaptopathy with intellectual regression

DLG4-related synaptopathy is a neurodevelopmental disorder caused by a DLG4 variant. We identified a novel de novo heterozygous frameshift variant, NM_001321075.3(DLG4):c.554_563del, in a Japanese girl. Intellectual regression without motor delay was observed at 2 years of age, and she was diagnosed with autism spectrum disorder and attention-deficit/hyperactivity disorder. Recognizing the possibility of DLG4-related synaptopathy in patients with intellectual regression is important for ensuring an accurate diagnosis.

Validation of the Austin Assessment: A screening tool for cerebral visual impairment related visual issues

Cerebral visual impairment is the most common cause of vision impairment affecting children in the economically developed world with a prevalence rate of approximately 3.4%. Currently there are limited options for screening for cerebral visual impairment, resulting in many children going undiagnosed, especially those that have normal visual acuity. The aim of this research was to validate an iPad App called the Austin Assessment, which was developed as a potential screening tool for cerebral visual impairment related visual issues. The research involved three separate phases: (1) creating a database of normative ranges for children aged 5-18 across the different variables of the Austin Assessment, (2) using the Austin Assessment to screen children aged 5-13 to assess the effectiveness of the Austin Assessment as a screening tool for CVI related visual issues, and (3) conducting specific validation research assessing children using the Austin Assessment and an already validated visual search tool. Each phase used different quantitative research methodologies to help show the effectiveness of the Austin Assessment as a screening tool for cerebral visual impairment related visual issues. From phase one of the research, thresholds were established for three variables of the Austin Assessment for the age groupings of 5-8, 9-12 and 13-18. If a child meets one of these thresholds this indicates further assessment is required to determine if they do in fact have cerebral visual impairment related visual issues. Phase two identified 17 children out of 270 who had clinical findings indicating visual issues; potentially indicative of CVI; investigation into the nature of these visual issues is ongoing. Phase three found that the Austin Assessment has moderate diagnostic value for each age group, with good sensitivity and specificity, making it effective at distinguishing those children who have visual issues from those who have typical vision. Further investigation is needed to confirm this initial validation.

Visual Behaviours (ViBes) in Cerebral Visual Impairment: Validating a Descriptive Tool to Support Diagnosis and Monitoring

Introduction

Cerebral visual impairment (CVI) is the most common cause of visual impairment in children in the UK. Diagnosis is based on identification of visual behaviours (ViBes) relating to visual dysfunction. Examination techniques and inventories have been developed to elicit these in children with a developmental age of two years or more. The absence of a structured approach to recording visual behaviours in children with complex needs is a barrier to diagnosis. The aim of the study was to develop a matrix of visual behaviours seen in pre-verbal and pre-motor children with visual impairment and establish its content validity and inter-rater reliability.

Methods

ViBe content validation:: Visual behaviour descriptors relating to visual function were collated and categorised by expert consensus of vision professionals into a matrix composed of three functions (attention, field/fixation, motor response) and five levels (0 = no awareness; 1 = visual awareness; 2 = visual attention; 3 = visual detection; 4 = visual understanding).ViBe inter-rater reliability:: The participants (two orthoptists, an optometrist, an ophthalmologist and two qualified teachers of the visually impaired) used the ViBe matrix to independently score each of 17 short video clips of children demonstrating visual behaviours seen in CVI.

Results

The ViBe matrix will be presented. Cohen's kappa for the matrix was 0.67, demonstrating moderate-to-strong inter-rater reliability.

Conclusion

The development of standardised descriptors can support clinicians and teachers in identifying areas of concern for children with complex needs. In addition, the ViBe matrix could be utilised in research, clinical and diagnostic reports to clearly communicate the areas of visual dysfunction and track progress resulting from interventions.

Key Points

The absence of a structured approach to recording visual behaviours in children with complex needs is a barrier to diagnosis.The ViBe matrix offers descriptors relating to visual behaviours and has demonstrated acceptable inter-rater reliability.The tool may support the identification and diagnosis of cerebral visual impairment in a population of children who cannot access standard testing.

NR2F1 shapes mitochondria in the mouse brain, providing new insights into Bosch-Boonstra-Schaaf optic atrophy syndrome

The nuclear receptor NR2F1 acts as a strong transcriptional regulator in embryonic and postnatal neural cells. In humans, mutations in the NR2F1 gene cause Bosch-Boonstra-Schaaf optic atrophy syndrome (BBSOAS), a rare neurodevelopmental disorder characterized by multiple clinical features including vision impairment, intellectual disability and autistic traits. In this study, we identified, by genome-wide and in silico analyses, a set of nuclear-encoded mitochondrial genes as potential genomic targets under direct NR2F1 transcriptional control in neurons. By combining mouse genetic, neuroanatomical and imaging approaches, we demonstrated that conditional NR2F1 loss of function within the adult mouse hippocampal neurogenic niche results in a reduced mitochondrial mass associated with mitochondrial fragmentation and downregulation of key mitochondrial proteins in newborn neurons, the genesis, survival and functional integration of which are impaired. Importantly, we also found dysregulation of several nuclear-encoded mitochondrial genes and downregulation of key mitochondrial proteins in the brain of Nr2f1-heterozygous mice, a validated BBSOAS model. Our data point to an active role for NR2F1 in the mitochondrial gene expression regulatory network in neurons and support the involvement of mitochondrial dysfunction in BBSOAS pathogenesis.

GRIN2A and GRIN2B and Their Related Phenotypes

Glutamate is the most relevant excitatory neurotransmitter of the central nervous system; it binds with several receptors, including N-methyl-D-aspartate receptors (NMDARs), a subtype of ionotropic glutamate receptor that displays voltage-dependent block by Mg2+ and a high permeability to Ca2+. GRIN2A and GRIN2B genes encode the GluN2A and GluN2B subunits of the NMDARs, which play important roles in synaptogenesis, synaptic transmission, and synaptic plasticity, as well as contributing to neuronal loss and dysfunction in several neurological disorders. Recently, individuals with a range of childhood-onset drug-resistant epilepsies, such as Landau–Kleffner or Lennox–Gastaut syndrome, intellectual disability (ID), and other neurodevelopmental abnormalities have been found to carry mutations in GRIN2A and GRIN2B, with high variable expressivity in phenotype. The first one is found mainly in epilepsy-aphasia syndromes, while the second one mainly in autism, schizophrenia, and ID, such as autism spectrum disorders. Brain magnetic resonance imaging alterations are found in some patients, even if without a clear clinical correlation. At the same time, increasing data on genotype–phenotype correlation have been found, but this is still not fully demonstrated. There are no specific therapies for the treatment of correlated NMDARs epilepsy, although some evidence with memantine, an antagonist of glutamate receptor, is reported in the literature in selected cases with mutation determining a gain of function.

Glycosylation and behavioral symptoms in neurological disorders

Glycosylation, the addition of glycans or carbohydrates to proteins, lipids, or other glycans, is a complex post-translational modification that plays a crucial role in cellular function. It is estimated that at least half of all mammalian proteins undergo glycosylation, underscoring its importance in the functioning of cells. This is reflected in the fact that a significant portion of the human genome, around 2%, is devoted to encoding enzymes involved in glycosylation. Changes in glycosylation have been linked to various neurological disorders, including Alzheimer's disease, Parkinson's disease, autism spectrum disorder, and schizophrenia. Despite its widespread occurrence, the role of glycosylation in the central nervous system remains largely unknown, particularly with regard to its impact on behavioral abnormalities in brain diseases. This review focuses on examining the role of three types of glycosylation: N-glycosylation, O-glycosylation, and O-GlcNAcylation, in the manifestation of behavioral and neurological symptoms in neurodevelopmental, neurodegenerative, and neuropsychiatric disorders.

Visual and cognitive profiles in children with and without cerebral visual impairment

Reliable differentiation of visual-perceptual difficulties in children with and without cerebral visual impairment (CVI) can often pose a diagnostic challenge. We, therefore, assessed the visual-perceptual profile in 94 children with and 77 children without suspected CVI between the ages of 8 and 17 years in a non-clinical setting, using a screening questionnaire and standardized visual-perceptual tests. Children with suspected CVI reported more frequently greater visual difficulties, had lower visual acuity, and were significantly impaired in visual search tests, in visual form and object perception, in visual space perception, and in visual text processing. There were no significant differences between groups in stereopsis, fixation stability, motility, horizontal saccadic eye movements, and convergence and accommodation. Cognitive performance in auditory attention and verbal short-term and working memory was similar in both groups. Our results indicate that the use of an appropriate questionnaire and specific visual-perceptual tests enables valid diagnostic detection of CVI. The additional use of cognitive tests also allows differentiation between primary and secondary impairments in visual perception.

The Role of Zinc and NMDA Receptors in Autism Spectrum Disorders

NMDA-type glutamate receptors are critical for synaptic plasticity in the central nervous system. Their unique properties and age-dependent arrangement of subunit types underpin their role as a coincidence detector of pre- and postsynaptic activity during brain development and maturation. NMDAR function is highly modulated by zinc, which is co-released with glutamate and concentrates in postsynaptic spines. Both NMDARs and zinc have been strongly linked to autism spectrum disorders (ASDs), suggesting that NMDARs are an important player in the beneficial effects observed with zinc in both animal models and children with ASDs. Significant evidence is emerging that these beneficial effects occur via zinc-dependent regulation of SHANK proteins, which form the backbone of the postsynaptic density. For example, dietary zinc supplementation enhances SHANK2 or SHANK3 synaptic recruitment and rescues NMDAR deficits and hypofunction in Shank3^ex13-16-/- and Tbr1^+/- ASD mice. Across multiple studies, synaptic changes occur in parallel with a reversal of ASD-associated behaviours, highlighting the zinc-dependent regulation of NMDARs and glutamatergic synapses as therapeutic targets for severe forms of ASDs, either pre- or postnatally. The data from rodent models set a strong foundation for future translational studies in human cells and people affected by ASDs.

NGLY1 deficiency: estimated incidence, clinical features, and genotypic spectrum from the NGLY1 Registry

PURPOSE

NGLY1 Deficiency is an ultra-rare, multisystemic disease caused by biallelic pathogenic NGLY1 variants. The aims of this study were to (1) characterize the variants and clinical features of the largest cohort of NGLY1 Deficiency patients reported to date, and (2) estimate the incidence of this disorder.

METHODS

The Grace Science Foundation collected genotypic data from 74 NGLY1 Deficiency patients, of which 37 also provided phenotypic data. We analyzed NGLY1 variants and clinical features and estimated NGLY1 disease incidence in the United States (U.S.).

RESULTS

Analysis of patient genotypes, including 10 previously unreported NGLY1 variants, showed strong statistical enrichment for missense variants in the transglutaminase-like domain of NGLY1 (p < 1.96E-11). Caregivers reported global developmental delay, movement disorder, and alacrima in over 85% of patients. Some phenotypic differences were noted between males and females. Regression was reported for all patients over 14 years old by their caregivers. The calculated U.S. incidence of NGLY1 Deficiency was ~ 12 individuals born per year.

CONCLUSION

The estimated U.S. incidence of NGLY1 indicates the disease may be more common than the number of patients reported in the literature suggests. Given the low frequency of most variants and proportion of compound heterozygotes, genotype/phenotype correlations were not distinguishable.

Characterizing Genotypes and Phenotypes Associated with Dysfunction of Channel-Encoding Genes in a Cohort of Patients with Intellectual Disability

BACKGROUND

Ion channel dysfunction in the brain can lead to impairment of neuronal membranes and generate several neurological diseases, especially neurodevelopmental disorders.

METHODS

In this study, we set out to delineate the genotype and phenotype spectrums of 14 Iranian patients from 7 families with intellectual disability (ID) and/or developmental delay (DD) in whom genetic mutations were identified by next-generation sequencing (NGS) in 7 channel-encoding genes: KCNJ10, KCNQ3, KCNK6, CACNA1C, CACNA1G, SCN8A, and GRIN2B. Moreover, the data of 340 previously fully reported ID and/or DD cases with a mutation in any of these seven genes were combined with our patients to clarify the genotype and phenotype spectrum in this group.

RESULTS

In total, the most common phenotypes in 354 cases with ID/DD in whom mutation in any of these 7 channel-encoding genes was identified were as follows: ID (77.4%), seizure (69.8%), DD (59.8%), behavioral abnormality (29.9%), hypotonia (21.7%), speech disorder (21.5%), gait disturbance (20.9%), and ataxia (20.3%). Electroencephalography abnormality (33.9%) was the major brain imaging abnormality.

CONCLUSION

The results of this study broaden the molecular spectrum of channel pathogenic variants associated with different clinical presentations in individuals with ID and/or DD.

An induced pluripotent stem cell-derived NMJ platform for study of the NGLY1-Congenital Disorder of Deglycosylation

There are many neurological rare diseases where animal models have proven inadequate or do not currently exist. NGLY1 Deficiency, a congenital disorder of deglycosylation, is a rare disease that predominantly affects motor control, especially control of neuromuscular action. In this study, NGLY1-deficient, patient-derived induced pluripotent stem cells (iPSCs) were differentiated into motoneurons (MNs) to identify disease phenotypes analogous to clinical disease pathology with significant deficits apparent in the NGLY1-deficient lines compared to the control. A neuromuscular junction (NMJ) model was developed using patient and wild type (WT) MNs to study functional differences between healthy and diseased NMJs. Reduced axon length, increased and shortened axon branches, MN action potential (AP) bursting and decreased AP firing rate and amplitude were observed in the NGLY1-deficient MNs in monoculture. When transitioned to the NMJ-coculture system, deficits in NMJ number, stability, failure rate, and synchronicity with indirect skeletal muscle (SkM) stimulation were observed. This project establishes a phenotypic NGLY1 model for investigation of possible therapeutics and investigations into mechanistic deficits in the system.

A fetus with Bosch-Boonstra-Schaaf optic atrophy syndrome characterized by bilateral ventricle widening: A case report and related literature review

RATIONALE

Bosch-Boonstra-Schaaf optic atrophy syndrome (BBSOAS) is a rare neurodevelopmental disorder caused by loss-of-function variants in the Nuclear Receptor Subfamily 2 Group F Member 1 (NR2F1). Here, we report a case of fetal BBSOAS. The fetus is typically featured by bilateral ventricle widening in the late second trimester, meanwhile, a 7.94-Mb deletion fragment on 5q14.3q15 involving the whole NR2F1 gene was confirmed by copy number variation sequencing (CNV-Seq) combined with karyotyping analysis. Our aim is to provide comprehensive prenatal clinical management strategy for fetal BBSOAS.

PATIENT CONCERNS

A 29-year-old primipara and her husband were referred to our prenatal diagnosis center due to the widening of bilateral ventricles at 29 + 1 weeks of gestation age.

DIAGNOSES

Ultrasound revealed the fetal widening posterior horns of bilateral ventricles at the GA of 27 + 3 weeks, 11 mm on the left and 10 mm on the right. At the following 29 + 1 weeks, ultrasound showed the posterior horn of the left lateral ventricle: 12 mm while the width of the right decreased to 9 mm, and intracranial arachnoid cyst. Furthermore, MRI confirmed that intracranial cyst might originate from an enlarged cisterna venae magnae cerebri, with mild dilation of 13.5 mm on the left ventricle. The fetal karyotyping analysis and CNV-Seq detection confirmed a 7.94-Mb deleted fragment on 5q14.3q15 (89340000_97280000) through the amniocentesis at 29 + 4 weeks of GA.

INTERVENTIONS

The fetus was closely monitored and underwent the following assessment by the multidisciplinary team.

OUTCOMES

The pregnancy was terminated in the end.

LESSONS

It is vital to use molecular and cytogenetical detections combined with a dynamic development history to make a definite diagnosis and evaluate the genetic status for the fetuses with BBSOAS.

Childhood visual impairment and blindness: 5-year data from a tertiary low vision center in Israel

BACKGROUND

To assess the main causes leading to childhood visual impairment/blindness in a center for low vision in Israel and to analyze the literature on pediatric blinding diseases in developed countries.

METHODS

Retrospective study based on observational case series. Data were obtained from medical records of visually impaired children, seen at a national referral low vision center. Children were divided into two groups: moderate visual impairment (6/18 to 6/60) and severe visual impairment (SVI)/blindness (<6/60). Inherited eye diseases (IED) were grouped together for analysis. Data from the Israeli blind registry from the same period of time were analyzed for comparison. A review of literature on childhood blindness in developed countries since 2000 was conducted.

RESULTS

A total of 1393 children aged 0-18 years were included in the study. Moderate visual impairment was seen in 1025 (73.6%) and SVI/blindness in 368 (26.4%) of the studied children. Among blind children, IED accounted for at least 51% of all diagnoses, including mainly albinism and retinal dystrophies. IED prevalence was equally high in both main ethnic groups (Jewish and Arab Muslims). Non-IED (22.6%) included mainly patients with cerebral visual impairment and retinopathy of prematurity.

CONCLUSIONS

The leading cause of childhood visual impairment and blindness in our patient cohort was IED. Analyses of the literature from the last two decades show that IED are a major cause for SVI/childhood blindness in other developed countries as well. Updated patterns of global childhood blindness may suggest a need for new approach for screening programs and modern tactics for prevention.

Phenotypic and genetic spectrum of ATP6V1A encephalopathy: a disorder of lysosomal homeostasis

Vacuolar-type H+-ATPase (V-ATPase) is a multimeric complex present in a variety of cellular membranes that acts as an ATP-dependent proton pump and plays a key role in pH homeostasis and intracellular signalling pathways. In humans, 22 autosomal genes encode for a redundant set of subunits allowing the composition of diverse V-ATPase complexes with specific properties and expression. Sixteen subunits have been linked to human disease. Here we describe 26 patients harbouring 20 distinct pathogenic de novo missense ATP6V1A variants, mainly clustering within the ATP synthase α/β family-nucleotide-binding domain. At a mean age of 7 years (extremes: 6 weeks, youngest deceased patient to 22 years, oldest patient) clinical pictures included early lethal encephalopathies with rapidly progressive massive brain atrophy, severe developmental epileptic encephalopathies and static intellectual disability with epilepsy. The first clinical manifestation was early hypotonia, in 70%; 81% developed epilepsy, manifested as developmental epileptic encephalopathies in 58% of the cohort and with infantile spasms in 62%; 63% of developmental epileptic encephalopathies failed to achieve any developmental, communicative or motor skills. Less severe outcomes were observed in 23% of patients who, at a mean age of 10 years and 6 months, exhibited moderate intellectual disability, with independent walking and variable epilepsy. None of the patients developed communicative language. Microcephaly (38%) and amelogenesis imperfecta/enamel dysplasia (42%) were additional clinical features. Brain MRI demonstrated hypomyelination and generalized atrophy in 68%. Atrophy was progressive in all eight individuals undergoing repeated MRIs. Fibroblasts of two patients with developmental epileptic encephalopathies showed decreased LAMP1 expression, Lysotracker staining and increased organelle pH, consistent with lysosomal impairment and loss of V-ATPase function. Fibroblasts of two patients with milder disease, exhibited a different phenotype with increased Lysotracker staining, decreased organelle pH and no significant modification in LAMP1 expression. Quantification of substrates for lysosomal enzymes in cellular extracts from four patients revealed discrete accumulation. Transmission electron microscopy of fibroblasts of four patients with variable severity and of induced pluripotent stem cell-derived neurons from two patients with developmental epileptic encephalopathies showed electron-dense inclusions, lipid droplets, osmiophilic material and lamellated membrane structures resembling phospholipids. Quantitative assessment in induced pluripotent stem cell-derived neurons identified significantly smaller lysosomes. ATP6V1A-related encephalopathy represents a new paradigm among lysosomal disorders. It results from a dysfunctional endo-lysosomal membrane protein causing altered pH homeostasis. Its pathophysiology implies intracellular accumulation of substrates whose composition remains unclear, and a combination of developmental brain abnormalities and neurodegenerative changes established during prenatal and early postanal development, whose severity is variably determined by specific pathogenic variants.

Genetic spectrum and characteristics of autosomal optic neuropathy in Korean: Use of next-generation sequencing in suspected hereditary optic atrophy

Aims

To evaluate the clinical characteristics and causative genetic variants in autosomal optic atrophy diagnosed using next-generation sequencing (NGS).

Methods

A cohort of 57 unrelated families affected with bilateral optic atrophy were recruited from two university-based tertiary referral hospitals from May 2016 to April 2022. Genetic variants were detected using a target enrichment panel consisting of 429 or 595 genes and known deep intronic variants associated with inherited eye diseases, exome sequencing, or genome sequencing. The results of detailed clinical examinations, disease-causing variants, and clinical diagnoses were analyzed.

Results

Among the 57 probands, 33 (57.9%) were men, and the median age at genetic testing was 19.1 years (interquartile range, 7.6–42.5 years). We identified 22 likely causative variants in 18 families and corresponding diagnostic yields of 31.6% (95% confidence interval, 21.0–44.5%). The diagnostic rate of NGS was higher in patients with infantile or early childhood onset optic atrophy than in those with late-onset or unknown optic atrophy (18/39, 46.2% vs. 0/18, 0%, P &lt; 0.001). Among the 22 variants, 15 were novel in our cohort. The OPA1 variants (n = 7) were found to be the major genetic causes, followed by the NR2F1 variant (n = 4). The causative variants in PTPN23, TMEM126A, NBAS, and WFS1 genes were identified in 4 probands with a recessive form of optic atrophy.

Conclusions

Based on the results of diagnostic NGS for optic atrophy, the causative variant could be detected in 31.6% of patients. Our study also demonstrated that NGS is unlikely to help identify molecular causes in late-onset unexplained optic atrophy.

Molecular Insights into the Role of Pathogenic nsSNPs in GRIN2B Gene Provoking Neurodevelopmental Disorders

The GluN2B subunit of N-methyl-D-aspartate receptors plays an important role in the physiology of different neurodevelopmental diseases. Genetic variations in the GluN2B coding gene (GRIN2B) have consistently been linked to West syndrome, intellectual impairment with focal epilepsy, developmental delay, macrocephaly, corticogenesis, brain plasticity, as well as infantile spasms and Lennox–Gastaut syndrome. It is unknown, however, how GRIN2B genetic variation impacts protein function. We determined the cumulative pathogenic impact of GRIN2B variations on healthy participants using a computational approach. We looked at all of the known mutations and calculated the impact of single nucleotide polymorphisms on GRIN2B, which encodes the GluN2B protein. The pathogenic effect, functional impact, conservation analysis, post-translation alterations, their driving residues, and dynamic behaviors of deleterious nsSNPs on protein models were then examined. Four polymorphisms were identified as phylogenetically conserved PTM drivers and were related to structural and functional impact: rs869312669 (p.Thr685Pro), rs387906636 (p.Arg682Cys), rs672601377 (p.Asn615Ile), and rs1131691702 (p.Ser526Pro). The combined impact of protein function is accounted for by the calculated stability, compactness, and total globularity score. GluN2B hydrogen occupancy was positively associated with protein stability, and solvent-accessible surface area was positively related to globularity. Furthermore, there was a link between GluN2B protein folding, movement, and function, indicating that both putative high and low local movements were linked to protein function. Multiple GRIN2B genetic variations are linked to gene expression, phylogenetic conservation, PTMs, and protein instability behavior in neurodevelopmental diseases. These findings suggest the relevance of GRIN2B genetic variations in neurodevelopmental problems.

Clinical, biochemical and genetic characteristics of MOGS-CDG: a rare congenital disorder of glycosylation

PURPOSE

To summarise the clinical, molecular and biochemical phenotype of mannosyl-oligosaccharide glucosidase-related congenital disorders of glycosylation (MOGS-CDG), which presents with variable clinical manifestations, and to analyse which clinical biochemical assay consistently supports diagnosis in individuals with bi-allelic variants in MOGS.

METHODS

Phenotypic characterisation was performed through an international and multicentre collaboration. Genetic testing was done by exome sequencing and targeted arrays. Biochemical assays on serum and urine were performed to delineate the biochemical signature of MOGS-CDG.

RESULTS

Clinical phenotyping revealed heterogeneity in MOGS-CDG, including neurological, immunological and skeletal phenotypes. Bi-allelic variants in MOGS were identified in 12 individuals from 11 families. The severity in each organ system was variable, without definite genotype correlation. Urine oligosaccharide analysis was consistently abnormal for all affected probands, whereas other biochemical analyses such as serum transferrin analysis was not consistently abnormal.

CONCLUSION

The clinical phenotype of MOGS-CDG includes multisystemic involvement with variable severity. Molecular analysis, combined with biochemical testing, is important for diagnosis. In MOGS-CDG, urine oligosaccharide analysis via matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry can be used as a reliable biochemical test for screening and confirmation of disease.

The Multidisciplinary Guidelines for Diagnosis and Referral in Cerebral Visual Impairment

Introduction

Cerebral visual impairment (CVI) is an important cause of visual impairment in western countries. Perinatal hypoxic-ischemic damage is the most frequent cause of CVI but CVI can also be the result of a genetic disorder. The majority of children with CVI have cerebral palsy and/or developmental delay. Early diagnosis is crucial; however, there is a need for consensus on evidence based diagnostic tools and referral criteria. The aim of this study is to develop guidelines for diagnosis and referral in CVI according to the grade method.

Patients and Methods

We developed the guidelines according to the GRADE method 5 searches on CVI (children, developmental age ≤ 18 years) were performed in the databases Medline, Embase, and Psychinfo, each with a distinct topic.

Results

Based on evidence articles were selected on five topics: 1. Medical history and CVI-questionnaires 23 (out of 1,007). 2. Ophthalmological and orthoptic assessment 37 (out of 816). 3. Neuropsychological assessment 5 (out of 716). 4. Neuroradiological evaluation and magnetic resonance imaging (MRI) 9 (out of 723). 5. Genetic assessment 5 (out of 458).

Conclusion

In medical history taking, prematurity low birth weight and APGAR (Appearance, Pulse, Grimace, Activity, Respiration) Scores (<5) are important. Different questionnaires are advised for children under the age of 3 years, older children and for specific risk groups (extremely preterm). In ophthalmological examination, eye movements, specially saccades, accommodation, crowding, contrast sensitivity and visual fields should be evaluated. OCT can show objective signs of trans-synaptic degeneration and abnormalities in fixation and saccades can be measured with eye tracking. Screening of visual perceptive functioning is recommended and can be directive for further assessment. MRI findings in CVI in Cerebral Palsy can be structured in five groups: Brain maldevelopment, white and gray matter lesions, postnatal lesions and a normal MRI. In children with CVI and periventricular leukomalacia, brain lesion severity correlates with visual function impairment. A differentiation can be made between cortical and subcortical damage and related visual function impairment. Additional assessments (neurological or genetic) can be necessary to complete the diagnosis of CVI and/or to reveal the etiology.

Visual Function and Neuropsychological Profile in Children with Cerebral Visual Impairment

Cerebral Visual Impairment (CVI) has become the leading cause of children’s visual impairment in developed countries. Since CVI may negatively affect neuropsychomotor development, an early diagnosis and characterization become fundamental to define effective habilitation approaches. To date, there is a lack of standardized diagnostic methods to assess CVI in children, and the role of visual functions in children’s neuropsychological profiles has been poorly investigated. In the present paper, we aim to describe the clinical and neuropsychological profiles and to investigate the possible effects of visual functions on neuropsychological performance of a cohort of children diagnosed with CVI. Fifty-one children with CVI were included in our retrospective analysis (inclusion criteria: verbal IQ > 70 in Wechsler scales; absence of significant ocular involvement). For each participant, we collected data on neuropsychological assessment (i.e., cognitive, cognitive visual, and learning abilities), basic visual functions (e.g., Best Corrected Visual Acuity—BCVA, contrast sensitivity, and ocular motor abilities) and global development features (e.g., neurological signs and motor development delay) based on standardized tests, according to patients’ ages. The results showed that oculomotor dysfunction involving saccades and smooth pursuit may be a core symptom of CVI and might have a significant impact on cognitive visual and other neuropsychological abilities. Furthermore, visual acuity and contrast sensitivity may influence cognitive, cognitive visual, and academic performances. Our findings suggest the importance of a comprehensive assessment of both visual and neuropsychological functions in children when CVI is suspected, which is needed to provide a more comprehensive functional profile and define the best habilitation strategy to sustain functional vision.

Genotype-phenotype spectrum and correlations in Xia-Gibbs syndrome: Report of five novel cases and literature review

Background

Xia‐Gibbs syndrome (XGS) is a rare neurodevelopmental disorder caused by pathogenic variants in the AT‐hook DNA‐binding motif‐containing 1 gene (AHDC1), encoding a protein with a crucial role in transcription and epigenetic regulation, axonogenesis, brain function, and neurodevelopment. AHDC1 variants possibly act through a dominant‐negative mechanism and may interfere with DNA repair processes, leading to genome instability and impaired DNA translesion repair. Variants affecting residues closer to the N‐terminal are thought to determine a milder phenotype with better cognitive performances. However, clean‐cut genotype–phenotype correlations are still lacking.

Cases

In this study, we investigated five subjects with XGS in whom exome sequencing led to the identification of five novel de novo pathogenic variants in AHDC1. All variants were extremely rare and predicted to cause a loss of protein function. The phenotype of the reported patients included developmental delay, hypotonia, and distinctive facial dysmorphisms. Additionally, uncommon clinical features were observed, including congenital hypothyroidism and peculiar skeletal abnormalities.

Conclusions

In this study, we report uncommon XGS features associated with five novel truncating variants in AHDC, thus expanding the genotype and phenotypic spectrum of this complex condition. We also compared our cases to previously reported cases, discussing the current status of genotype–phenotype correlations in XGS.

Delineating the epilepsy phenotype of NGLY1 deficiency

We delineated the phenotypic spectrum of epilepsy in individuals with NGLY1 deficiency from an international cohort. We collected detailed clinical and electroencephalographic data from 29 individuals with bi-allelic (likely) pathogenic variants in NGLY1 as part of an ongoing prospective natural history study. Participants were evaluated in-person at a single center and/or remotely. Historical medical records were reviewed. Published cases were included for comprehensive phenotyping. Of 29 individuals (mean 11.4 years, range 3-27 years), 17 (58.6%) participants had a history of epilepsy. Seizure onset was in early childhood (mean 43 months, range 2 months to 19 years). The most common seizure types were myoclonic and atonic. Epilepsy course was variable, but 35.2% (6/17) of participants with epilepsy achieved seizure freedom. The most common medications included levetiracetam, valproate, lamotrigine, and clobazam. Electroencephalogram (EEGs) were abnormal in 80% (12/15) of participants with or without epilepsy, although encephalopathy was uncommon. There was a trend in neurodevelopmental outcomes that participants with epilepsy had more developmental delays. In summary, epilepsy is common in NGLY1 deficiency. Over half of the participants had a history of epilepsy and nearly all had EEG abnormalities indicating an increased risk of epilepsy. This work expands the electroclinical phenotype of NGLY1 deficiency and supports a high clinical suspicion for seizures. Some of the more common seizure types (epileptic spasms, myoclonic, and atonic seizures) can be subtle and require counseling to ensure early recognition and treatment to ensure the best possible outcomes. Despite transient liver enzyme abnormalities in this disorder, hepatically metabolized medications were well tolerated.

NGLY1 Deficiency, a Congenital Disorder of Deglycosylation: From Disease Gene Function to Pathophysiology

N-Glycanase 1 (NGLY1) is a cytosolic enzyme involved in removing N-linked glycans of misfolded N-glycoproteins and is considered to be a component of endoplasmic reticulum-associated degradation (ERAD). The 2012 identification of recessive NGLY1 mutations in a rare multisystem disorder has led to intense research efforts on the roles of NGLY1 in animal development and physiology, as well as the pathophysiology of NGLY1 deficiency. Here, we present a review of the NGLY1-deficient patient phenotypes, along with insights into the function of this gene from studies in rodent and invertebrate animal models, as well as cell culture and biochemical experiments. We will discuss critical processes affected by the loss of NGLY1, including proteasome bounce-back response, mitochondrial function and homeostasis, and bone morphogenetic protein (BMP) signaling. We will also cover the biologically relevant targets of NGLY1 and the genetic modifiers of NGLY1 deficiency phenotypes in animal models. Together, these discoveries and disease models have provided a number of avenues for preclinical testing of potential therapeutic approaches for this disease.

GABRB2, a key player in neuropsychiatric disorders and beyond

The GABA receptors represent the main inhibitory system in the central nervous system that ensure synaptogenesis, neurogenesis, and the regulation of neuronal plasticity and learning. GABAA receptors are pentameric in structure and belong to the Cys-loop superfamily. The GABRB2 gene, located on chromosome 5q34, encodes the β2 subunit that combines with the α and γ subunits to form the major subtype of GABAA receptors, which account for 43% of all GABAA receptors in the mammalian brain. Each subunit probably consists of an extracellular N-terminal domain, four membrane-spanning segments, a large intracellular loop between TM3 and TM4, and an extracellular C-terminal domain. Alternative splicing of the RNA transcript of the GABRB2 gene gives rise at least to four long and short isoforms with dissimilar electrophysiological properties. Furthermore, GABRB2 is imprinted and subjected to epigenetic regulation and positive selection. It has been associated with schizophrenia first in Han Chinese, and subsequently validated in other populations. Gabrb2 knockout mice also exhibited schizophrenia-like behavior and neuroinflammation that were ameliorated by the antipsychotic drug risperidone. GABRB2 was also associated with other neuropsychiatric disorders including bipolar disorder, epilepsy, autism spectrum disorder, Alzheimer's disease, frontotemporal dementia, substance dependence, depression, internet gaming disorder, and premenstrual dysphoric disorder. Recently, it has been postulated that GABRB2 might be a potential marker for different cancer types. As GABRB2 has a pivotal role in the central nervous system and is increasingly recognized to contribute to human diseases, further understanding of its structure and function may expedite the generation of new therapeutic approaches.

Structural and Functional Aspects of the Neurodevelopmental Gene NR2F1: From Animal Models to Human Pathology

The assembly and maturation of the mammalian brain result from an intricate cascade of highly coordinated developmental events, such as cell proliferation, migration, and differentiation. Any impairment of this delicate multi-factorial process can lead to complex neurodevelopmental diseases, sharing common pathogenic mechanisms and molecular pathways resulting in multiple clinical signs. A recently described monogenic neurodevelopmental syndrome named Bosch-Boonstra-Schaaf Optic Atrophy Syndrome (BBSOAS) is caused by NR2F1 haploinsufficiency. The NR2F1 gene, coding for a transcriptional regulator belonging to the steroid/thyroid hormone receptor superfamily, is known to play key roles in several brain developmental processes, from proliferation and differentiation of neural progenitors to migration and identity acquisition of neocortical neurons. In a clinical context, the disruption of these cellular processes could underlie the pathogenesis of several symptoms affecting BBSOAS patients, such as intellectual disability, visual impairment, epilepsy, and autistic traits. In this review, we will introduce NR2F1 protein structure, molecular functioning, and expression profile in the developing mouse brain. Then, we will focus on Nr2f1 several functions during cortical development, from neocortical area and cell-type specification to maturation of network activity, hippocampal development governing learning behaviors, assembly of the visual system, and finally establishment of cortico-spinal descending tracts regulating motor execution. Whenever possible, we will link experimental findings in animal or cellular models to corresponding features of the human pathology. Finally, we will highlight some of the unresolved questions on the diverse functions played by Nr2f1 during brain development, in order to propose future research directions. All in all, we believe that understanding BBSOAS mechanisms will contribute to further unveiling pathophysiological mechanisms shared by several neurodevelopmental disorders and eventually lead to effective treatments.

NR2F1 database: 112 variants and 84 patients support refining the clinical synopsis of Bosch-Boonstra-Schaaf optic atrophy syndrome

Pathogenic variants of the nuclear receptor subfamily 2 group F member 1 gene (NR2F1) are responsible for Bosch-Boonstra-Schaaf optic atrophy syndrome (BBSOAS), an autosomal dominant disorder characterized by optic atrophy associated with developmental delay and intellectual disability, but with a clinical presentation which appears to be multifaceted. We created the first public locus-specific database dedicated to NR2F1. All variants and clinical cases reported in the literature, as well as new unpublished cases, were integrated into the database using standard nomenclature to describe both molecular and phenotypic anomalies. We subsequently pursued a comprehensive approach based on computed representation and analysis suggesting a refinement of the BBSOAS clinical description with respect to neurological features and the inclusion of additional signs of hypotonia and feeding difficulties. This database is fully accessible for both clinician and molecular biologists and should prove useful in further refining the clinical synopsis of NR2F1 as new data is recorded.

Tracking-Based Interactive Assessment of Saccades, Pursuits, Visual Field, and Contrast Sensitivity in Children With Brain Injury

Visual deficits in children that result from brain injury, including cerebral/cortical visual impairment (CVI), are difficult to assess through conventional methods due to their frequent co-occurrence with cognitive and communicative disabilities. Such impairments hence often go undiagnosed or are only determined through subjective evaluations of gaze-based reactions to different forms, colors, and movements, which limits any potential for remediation. Here, we describe a novel approach to grading visual health based on eye movements and evidence from gaze-based tracking behaviors. Our approach—the “Visual Ladder”—reduces reliance on the user’s ability to attend and communicate. The Visual Ladder produces metrics that quantify spontaneous saccades and pursuits, assess visual field responsiveness, and grade spatial visual function from tracking responses to moving stimuli. We used the Ladder to assess fourteen hospitalized children aged 3 to 18 years with a diverse range of visual impairments and causes of brain injury. Four children were excluded from analysis due to incompatibility with the eye tracker (e.g., due to severe strabismus). The remaining ten children—including five non-verbal children—were tested multiple times over periods ranging from 2 weeks to 9 months, and all produced interpretable outcomes on at least three of the five visual tasks. The results suggest that our assessment tasks are viable in non-communicative children, provided their eyes can be tracked, and hence are promising tools for use in a larger clinical study. We highlight and discuss informative outcomes exhibited by each child, including directional biases in eye movements, pathological nystagmus, visual field asymmetries, and contrast sensitivity deficits. Our findings indicate that these methodologies will enable the rapid, objective classification and grading of visual impairments in children with CVI, including non-verbal children who are currently precluded from most vision assessments. This would provide a much-needed differential diagnostic and prognostic tool for CVI and other impairments of the visual system, both ocular and cerebral.

A homozygous GRIN1 null variant causes a more severe phenotype of early infantile epileptic encephalopathy

Pathogenic variants in glutamate receptor, ionotropic, NMDA-1 (GRIN1) cause an autosomal dominant or recessive neurodevelopmental disorder with global developmental delay, with or without seizures (AD or AR GRIN1-NDD). Here, we describe a novel homozygous canonical splice site variant in GRIN1 in a 12-month-old boy with early infantile epileptic encephalopathy and severe global developmental delay. This represents only the second family with a homozygous predicted-null variant in GRIN1 reported to date. We review the published literature on AR GRIN1-NDD and find that the phenotype in our patient is much more severe than those seen with homozygous missense variants. A similarly severe phenotype of intractable epilepsy and infantile death has only been reported in one other family with a homozygous nonsense variant in GRIN1. We, therefore, propose that biallelic predicted-null variants in GRIN1 can cause a markedly more severe clinical phenotype than AR GRIN1-NDD caused by missense variants.

Developmental disabilities across the world: A scientometric review from 1936 to 2020

BACKGROUND

Developmental disabilities have been largely studied in the past years. Their etiological mechanisms have been underpinned to the interactions between genetic and environmental factors. These factors show variability across the world. Thus, it is important to understand where the set of knowledge obtained on developmental disabilities originates from and whether it is generalizable to low- and middle-income countries.

AIMS

This study aims to understand the origins of the available literature on developmental disabilities, keeping a focus on parenting, and identify the main trend of research.

METHODS AND PROCEDURE

A sample of 11,315 publications from 1936 to 2020 were collected from Scopus and a graphical country analysis was conducted. Furthermore, a qualitative approach enabled the clustering of references by keywords into four main areas: "Expression of the disorder", "Physiological Factors", "How it is studied" and "Environmental factors". For each area, a document co-citation analysis (DCA) on CiteSpace software was performed.

OUTCOMES AND RESULTS

Results highlight the leading role of North America in the study of developmental disabilities. Trends in the literature and the documents' scientific relevance are discussed in details.

CONCLUSIONS AND IMPLICATIONS

Results demand for investigation in different socio-economical settings to generalize our knowledge. What this paper adds? The current paper tries to provide insight into the origins of the literature on developmental disabilities with a focus on parenting, together with an analysis of the trends of research in the field. The paper consisted of a multi-disciplinary and multi-method review. In fact, the review tried to integrate the analysis of the relation between developmental disabilities with a closer look at the scientific contributions to the field across the world. Specifically, the paper integrates a total of 11,315 papers published on almost a century of research (from 1936 to 2020). An initial qualitative analysis on keywords was combined to a subsequent quantitative approach in order to maximize the comprehension of the impact of almost a century of scientific contributions. Specifically, documents were studied with temporal and structural metrics on a scientometric approach. This allowed the exploration of patterns within the literature available on Scopus in a quantitative way. This method not only assessed the importance of single documents within the network. As a matter of fact, the document co-citation analysis used on CiteSpace software provided insight into the relations existing between multiple documents in the field of research. As a result, the leading role of North America in the literature of developmental disabilities and parenting emerged. This was accompanied by the review of the main trends of research within the existing literature.

Physiological importance of NGLY1, as revealed by rodent model analyses

Cytosolic peptide:N-glycanase (NGLY1) is an enzyme that cleaves N-glycans from glycoproteins that has been retrotranslocated from the endoplasmic reticulum (ER) lumen into the cytosol. It is known that NGLY1 is involved in the degradation of cytosolic glycans (non-lysosomal glycan degradation) as well as ER-associated degradation (ERAD), a quality control system for newly synthesized glycoproteins. The discovery of NGLY1 deficiency, which is caused by mutations in the human NGLY1 gene and results in multisystemic symptoms, has attracted interest in the physiological functions of NGLY1 in mammals. Studies using various animal models led to the identification of possible factors that contribute to the pathogenesis of NGLY1 deficiency. In this review, we summarize phenotypic consequences that have been reported for various Ngly1-deficient rodent models, and discuss future perspectives to provide more insights into the physiological functions of NGLY1.

Ngly1 -/- rats develop neurodegenerative phenotypes and pathological abnormalities in their peripheral and central nervous systems

N-glycanase 1 (NGLY1) deficiency, an autosomal recessive disease caused by mutations in the NGLY1 gene, is characterized by developmental delay, hypolacrima or alacrima, seizure, intellectual disability, movement disorders and other neurological phenotypes. Because of few animal models that recapitulate these clinical signatures, the mechanisms of the onset of the disease and its progression are poorly understood, and the development of therapies is hindered. In this study, we generated the systemic Ngly1-deficient rodent model, Ngly1^−/− rats, which showed developmental delay, movement disorder, somatosensory impairment and scoliosis. These phenotypes in Ngly1^−/− rats are consistent with symptoms in human patients. In accordance with the pivotal role played by NGLY1 in endoplasmic reticulum-associated degradation processes, cleaving N-glycans from misfolded glycoproteins in the cytosol before they can be degraded by the proteasome, loss of Ngly1 led to accumulation of cytoplasmic ubiquitinated proteins, a marker of misfolded proteins in the neurons of the central nervous system of Ngly1^−/− rats. Histological analysis identified prominent pathological abnormalities, including necrotic lesions, mineralization, intra- and extracellular eosinophilic bodies, astrogliosis, microgliosis and significant loss of mature neurons in the thalamic lateral and the medial parts of the ventral posterior nucleus and ventral lateral nucleus of Ngly1^−/− rats. Axonal degradation in the sciatic nerves was also observed, as in human subjects. Ngly1^−/− rats, which mimic the symptoms of human patients, will be a useful animal model for preclinical testing of therapeutic options and understanding the detailed mechanisms of NGLY1 deficiency.

A de novo GRIN1 Variant Associated With Myoclonus and Developmental Delay: From Molecular Mechanism to Rescue Pharmacology

N-Methyl-D-aspartate receptors (NMDARs) are highly expressed in brain and play important roles in neurodevelopment and various neuropathologic conditions. Here, we describe a new phenotype in an individual associated with a novel de novo deleterious variant in GRIN1 (c.1595C>A, p.Pro532His). The clinical phenotype is characterized with developmental encephalopathy, striking stimulus-sensitive myoclonus, and frontal lobe and frontal white matter hypoplasia, with no apparent seizures detected. NMDARs that contained the P532H within the glycine-binding domain of GluN1 with either the GluN2A or GluN2B subunits were evaluated for changes in their pharmacological and biophysical properties, which surprisingly revealed only modest changes in glycine potency but a significant decrease in glutamate potency, an increase in sensitivity to endogenous zinc inhibition, a decrease in response to maximally effective concentrations of agonists, a shortened synaptic-like response time course, a decreased channel open probability, and a reduced receptor cell surface expression. Molecule dynamics simulations suggested that the variant can lead to additional interactions across the dimer interface in the agonist-binding domains, resulting in a more open GluN2 agonist-binding domain cleft, which was also confirmed by single-molecule fluorescence resonance energy transfer measurements. Based on the functional deficits identified, several positive modulators were evaluated to explore potential rescue pharmacology.

Two de novo GluN2B mutations affect multiple NMDAR-functions and instigate severe pediatric encephalopathy

The N-methyl-D-aspartate receptors (NMDARs; GluNRS) are glutamate receptors, commonly located at excitatory synapses. Mutations affecting receptor function often lead to devastating neurodevelopmental disorders. We have identified two toddlers with different heterozygous missense mutations of the same, and highly conserved, glycine residue located in the ligand-binding-domain of GRIN2B: G689C and G689S. Structure simulations suggest severely impaired glutamate binding, which we confirm by functional analysis. Both variants show three orders of magnitude reductions in glutamate EC₅₀, with G689S exhibiting the largest reductions observed for GRIN2B (~2000-fold). Moreover, variants multimerize with, and upregulate, GluN2Bwt-subunits, thus engendering a strong dominant-negative effect on mixed channels. In neurons, overexpression of the variants instigates suppression of synaptic GluNRs. Lastly, while exploring spermine potentiation as a potential treatment, we discovered that the variants fail to respond due to G689’s novel role in proton-sensing. Together, we describe two unique variants with extreme effects on channel function. We employ protein-stability measures to explain why current (and future) LBD mutations in GluN2B primarily instigate Loss-of-Function.

Reversibility of motor dysfunction in the rat model of NGLY1 deficiency

N-glycanase 1 (NGLY1) deficiency is a rare inherited disorder characterized by developmental delay, hypolacrima or alacrima, seizure, intellectual disability, motor deficits, and other neurological symptoms. The underlying mechanisms of the NGLY1 phenotype are poorly understood, and no effective therapy is currently available. Similar to human patients, the rat model of NGLY1 deficiency, Ngly1-/-, shows developmental delay, movement disorder, somatosensory impairment, scoliosis, and learning disability. Here we show that single intracerebroventricular administration of AAV9 expressing human NGLY1 cDNA (AAV9-hNGLY1) to Ngly1-/- rats during the weaning period restored NGLY1 expression in the brain and spinal cord, concomitant with increased enzymatic activity of NGLY1 in the brain. hNGLY1 protein expressed by AAV9 was found predominantly in mature neurons, but not in glial cells, of Ngly1-/- rats. Strikingly, intracerebroventricular administration of AAV9-hNGLY1 normalized the motor phenotypes of Ngly1-/- rats assessed by the rota-rod test and gait analysis. The reversibility of motor deficits in Ngly1-/- rats by central nervous system (CNS)-restricted gene delivery suggests that the CNS is the primary therapeutic target organs for NGLY1 deficiency, and that the Ngly1-/- rat model may be useful for evaluating therapeutic treatments in pre-clinical studies.

Cerebral visual impairment-related vision problems in primary school children: a cross-sectional survey

AIM

To estimate how many children in mainstream primary schools have cerebral visual impairment (CVI)-related vision problems and to investigate whether some indicators might be useful as red flags, if they were associated with increased risk for these problems.

METHOD

We conducted a survey of primary school children aged 5 to 11 years, using whether they were getting extra educational help and/or teacher- and parent-reported behaviour questionnaires to identify children at risk for CVI. These and a random 5% sample were assessed for CVI-related vision problems. We compared the usefulness of potential red flags using likelihood ratios.

RESULTS

We received questionnaires on 2298 mainstream-educated children and examined 248 children (152 [61%] males, 96 females [39%]; mean age 8y 1mo, SD 20mo, range 5y 6mo-11y 8mo). We identified 78 out of 248 children (31.5% of those examined, 3.4% of the total sample), who had at least one CVI-related vision problem. The majority (88%) were identified by one or more red flag but none were strongly predictive. Fewer than one in five children with any CVI-related vision problem had reduced visual acuity.

INTERPRETATION

Children with CVI-related vision problems were more prevalent than has been appreciated. Assessment of at-risk children may be useful so that opportunities to improve outcomes for children with CVI-related vision problems are not missed.