CHD8-related disorders redefined: an expanding spectrum of dystonic phenotypes

BACKGROUND

Heterozygous loss-of-function variants in CHD8 have been associated with a syndromic neurodevelopmental-disease spectrum, collectively referred to as CHD8-related neurodevelopmental disorders. Several different clinical manifestations, affecting neurodevelopmental and systemic domains, have been described, presenting with highly variable expressivity. Some expressions are well established and comprise autism spectrum disorders, psychomotor delay with cognitive impairment, postnatal overgrowth with macrocephaly, structural brain abnormalities, gastrointestinal disturbances, and behavioral and sleep-pattern problems. However, the complete phenotypic spectrum of CHD8-related disorders is still undefined. In 2021, our group described two singular female patients with CHD8-related neurodevelopmental disorder and striking dystonic manifestations, prompting the suggestion that dystonia should be considered a possible component of this condition.

CASE SERIES PRESENTATION

We describe three additional unrelated female individuals, each carrying a different CHD8 frameshift variant and whose clinical presentations were primarily characterized by young-onset dystonia. Their dystonic manifestations were remarkably heterogeneous and ranged from focal, exercise-dependent, apparently isolated forms to generalized permanent phenotypes accompanied by spasticity and tremor. Neurocognitive impairment and autistic behaviors, typical of CHD8-related disorders, were virtually absent or at the mild end of the spectrum.

CONCLUSIONS

This work validates our previous observation that dystonia is part of the phenotypic spectrum of CHD8-related neurodevelopmental disorders with potential female preponderance, raising new challenges and opportunities in the diagnosis and management of this condition. It also highlights the importance of in-depth neurologic phenotyping of patients carrying variants associated with neurodevelopmental disorders, as the connection between neurodevelopmental and movement disorders is proving closer than previously appreciated.

Biallelic MED27 variants lead to variable ponto-cerebello-lental degeneration with movement disorders

MED27 is a subunit of the Mediator multiprotein complex, which is involved in transcriptional regulation. Biallelic MED27 variants have recently been suggested to be responsible for an autosomal recessive neurodevelopmental disorder with spasticity, cataracts and cerebellar hypoplasia. We further delineate the clinical phenotype of MED27-related disease by characterizing the clinical and radiological features of 57 affected individuals from 30 unrelated families with biallelic MED27 variants. Using exome sequencing and extensive international genetic data sharing, 39 unpublished affected individuals from 18 independent families with biallelic missense variants in MED27 have been identified (29 females, mean age at last follow-up 17 ± 12.4 years, range 0.1-45). Follow-up and hitherto unreported clinical features were obtained from the published 12 families. Brain MRI scans from 34 cases were reviewed. MED27-related disease manifests as a broad phenotypic continuum ranging from developmental and epileptic-dyskinetic encephalopathy to variable neurodevelopmental disorder with movement abnormalities. It is characterized by mild to profound global developmental delay/intellectual disability (100%), bilateral cataracts (89%), infantile hypotonia (74%), microcephaly (62%), gait ataxia (63%), dystonia (61%), variably combined with epilepsy (50%), limb spasticity (51%), facial dysmorphism (38%) and death before reaching adulthood (16%). Brain MRI revealed cerebellar atrophy (100%), white matter volume loss (76.4%), pontine hypoplasia (47.2%) and basal ganglia atrophy with signal alterations (44.4%). Previously unreported 39 affected individuals had seven homozygous pathogenic missense MED27 variants, five of which were recurrent. An emerging genotype-phenotype correlation was observed. This study provides a comprehensive clinical-radiological description of MED27-related disease, establishes genotype-phenotype and clinical-radiological correlations and suggests a differential diagnosis with syndromes of cerebello-lental neurodegeneration and other subtypes of 'neuro-MEDopathies'.

Loss-of-function variants in CUL3 cause a syndromic neurodevelopmental disorder

Purpose

De novo variants in CUL3 (Cullin-3 ubiquitin ligase) have been strongly associated with neurodevelopmental disorders (NDDs), but no large case series have been reported so far. Here we aimed to collect sporadic cases carrying rare variants in CUL3, describe the genotype-phenotype correlation, and investigate the underlying pathogenic mechanism.

Methods

Genetic data and detailed clinical records were collected via multi-center collaboration. Dysmorphic facial features were analyzed using GestaltMatcher. Variant effects on CUL3 protein stability were assessed using patient-derived T-cells.

Results

We assembled a cohort of 35 individuals with heterozygous CUL3 variants presenting a syndromic NDD characterized by intellectual disability with or without autistic features. Of these, 33 have loss-of-function (LoF) and two have missense variants. CUL3 LoF variants in patients may affect protein stability leading to perturbations in protein homeostasis, as evidenced by decreased ubiquitin-protein conjugates in vitro . Specifically, we show that cyclin E1 (CCNE1) and 4E-BP1 (EIF4EBP1), two prominent substrates of CUL3, fail to be targeted for proteasomal degradation in patient-derived cells.

Conclusion

Our study further refines the clinical and mutational spectrum of CUL3 -associated NDDs, expands the spectrum of cullin RING E3 ligase-associated neuropsychiatric disorders, and suggests haploinsufficiency via LoF variants is the predominant pathogenic mechanism.

Mechanobiology of the relocation of proteins in advecting cells: in vitro experiments, multi-physics modeling, and simulations

Cell motility-a cellular behavior of paramount relevance in embryonic development, immunological response, metastasis, or angiogenesis-demands a mechanical deformation of the cell membrane and influences the surface motion of molecules and their biochemical interactions. In this work, we develop a fully coupled multi-physics model able to capture and predict the protein flow on endothelial advecting plasma membranes. The model has been validated against co-designed in vitro experiments. The complete picture of the receptor dynamics has been understood, and limiting factors have been identified together with the laws that regulate receptor polarization. This computational approach might be insightful in the prediction of endothelial cell behavior in different tumoral environments, circumventing the time-consuming and expensive empirical characterization of each tumor.

Highlighting the Dystonic Phenotype Related to GNAO1

BACKGROUND

Most reported patients carrying GNAO1 mutations showed a severe phenotype characterized by early-onset epileptic encephalopathy and/or chorea.

OBJECTIVE

The aim was to characterize the clinical and genetic features of patients with mild GNAO1-related phenotype with prominent movement disorders.

METHODS

We included patients diagnosed with GNAO1-related movement disorders of delayed onset (>2 years). Patients experiencing either severe or profound intellectual disability or early-onset epileptic encephalopathy were excluded.

RESULTS

Twenty-four patients and 1 asymptomatic subject were included. All patients showed dystonia as prominent movement disorder. Dystonia was focal in 1, segmental in 6, multifocal in 4, and generalized in 13. Six patients showed adolescence or adulthood-onset dystonia. Seven patients presented with parkinsonism and 3 with myoclonus. Dysarthria was observed in 19 patients. Mild and moderate ID were present in 10 and 2 patients, respectively.

CONCLUSION

We highlighted a mild GNAO1-related phenotype, including adolescent-onset dystonia, broadening the clinical spectrum of this condition. © 2022 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Childhood-onset progressive dystonia associated with pathogenic truncating variants in CHD8

Originally described as a risk factor for autism, CHD8 loss‐of‐function variants have recently been associated with a wider spectrum of neurodevelopmental abnormalities. We further expand the CHD8‐related phenotype with the description of two unrelated patients who presented with childhood‐onset progressive dystonia. Whole‐exome sequencing conducted in two independent laboratories revealed a CHD8 nonsense variant in one patient and a frameshift variant in the second. The patients had strongly overlapping phenotypes characterized by generalized dystonia with mild‐to‐moderate neurodevelopmental comorbidity. Deep brain stimulation led to clinical improvement in both cases. We suggest that CHD8 should be added to the growing list of neurodevelopmental disorder‐associated genes whose mutations can also result in dystonia‐dominant phenotypes.

Rare deleterious de novo missense variants in Rnf2/Ring2 are associated with a neurodevelopmental disorder with unique clinical features

The Polycomb group (PcG) gene RNF2 (RING2) encodes a catalytic subunit of the Polycomb repressive complex 1 (PRC1), an evolutionarily conserved machinery that post-translationally modifies chromatin to maintain epigenetic transcriptional repressive states of target genes including Hox genes. Here, we describe two individuals, each with rare de novo missense variants in RNF2. Their phenotypes include intrauterine growth retardation, severe intellectual disabilities, behavioral problems, seizures, feeding difficulties and dysmorphic features. Population genomics data suggest that RNF2 is highly constrained for loss-of-function (LoF) and missense variants, and both p.R70H and p.S82R variants have not been reported to date. Structural analyses of the two alleles indicate that these changes likely impact the interaction between RNF2 and BMI1, another PRC1 subunit or its substrate Histone H2A, respectively. Finally, we provide functional data in Drosophila that these two missense variants behave as LoF alleles in vivo. The evidence provide support for deleterious alleles in RNF2 being associated with a new and recognizable genetic disorder. This tentative gene-disease association in addition to the 12 previously identified disorders caused by PcG genes attests to the importance of these chromatin regulators in Mendelian disorders.

MED27 Variants Cause Developmental Delay, Dystonia, and Cerebellar Hypoplasia

The Mediator multiprotein complex functions as a regulator of RNA polymerase II-catalyzed gene transcription. In this study, exome sequencing detected biallelic putative disease-causing variants in MED27, encoding Mediator complex subunit 27, in 16 patients from 11 families with a novel neurodevelopmental syndrome. Patient phenotypes are highly homogeneous, including global developmental delay, intellectual disability, axial hypotonia with distal spasticity, dystonic movements, and cerebellar hypoplasia. Seizures and cataracts were noted in severely affected individuals. Identification of multiple patients with biallelic MED27 variants supports the critical role of MED27 in normal human neural development, particularly for the cerebellum. ANN NEUROL 2021;89:828-833.

Role of VEGFs in metabolic disorders

Obesity and metabolic disorders are important public health problems. In this review, the role of vasculature network and VEGF in the adipose tissue maintenance and supplementation is discussed. Angiogenesis is a key process implicated in regulation of tissues homeostasis. Dysregulation of new blood vessels formation may be crucial and contribute to the onset of several pathological conditions, including metabolic syndrome-associated disorders. Adipose tissue homeostasis is fine regulated by vascular network. Vessels support adipose structure. Vasculature modulates the balance between positive and negative regulator factors. In white adipose tissue, vascular endothelial growth factor (VEGF) controls the metabolic activities of adipocytes promoting the trans-differentiation from white to beige phenotype. Trans-differentiation results in an increase of energy consumption. VEGF exerts an opposite effect on brown adipose tissue, where VEGF increases oxygen supply and improves energy expenditure inducing the whitening of adipocytes.

Near-Infrared Spectroscopy Monitoring, Superior Vena Cava Flow, and Neurodevelopmental Outcome at 2 years in a Cohort of Very Low-Birth-Weight Infants

Objective We aimed at assessing the association between superior vena cava flow (SVCf), regional (cerebral) tissue oxygen saturation (rSO2), and cerebral fractional oxygen extraction (CFOE) during the first 48 hours of life and 2-years neurodevelopmental outcome of very low-birth-weight infants (VLBW). Methods We prospectively studied 60 VLBW infants admitted to our neonatal intensive care unit; rSO2 was continuously monitored with near-infrared spectroscopy during the first 48 hours of life, SVCf was measured at 4 to 6, 12, 24, and 48 hours, and CFOE was calculated. Neurodevelopmental outcome was assessed at 24 months corrected age. Results The mean gestational age at birth was 27.9 weeks (standard deviation: 2.4); 8 infants died in the first 3 months of life, 6 were lost to follow-up, 46 survived and were followed up. At 24 months, 6 (13%) and 7 (15.2%) infants developed minor and major sequelae, respectively. Infants who died had higher CFOE (p < 0.001) and lower SVCf (p < 0.001) than infants surviving with sequelae. In turn, these had higher SVCf between 24 and 48 hours than those without sequelae (p < 0.001). Conclusion SVCf, rSO2, and CFOE patterns in the first days of life suggest cerebral hyperperfusion, related to loss of autoregulation and/or use of inotropic drugs, as a potential mechanism of cerebral injury.

What is the "ideal" grading system for the junior surgery clerkship?

BACKGROUND

There is currently no consistency in grading systems for clinical clerkships across medical schools.

METHODS

Surgery clerkship directors were surveyed regarding their current grading categories, distribution of grades across levels, and opinions about the "ideal" grading system.

RESULTS

Responses were received from 103 of 134 schools (77%). The following grading systems were employed: numerical scores, 1%; points, 1%; pass/fail, 5%; letter grades, 19%; and descriptor terms, 74%. Institutions used the following number of grading categories: 2, 5%; 3, 18%; 4, 35%; 5, 37%; 6, 3%; and 7, 1%. There was considerable variation between schools in frequency distributions across levels. Half of clerkship directors were satisfied with their system, and most considered an ideal system to consist of 4 or 5 descriptors.

CONCLUSIONS

We believe an optimal clerkship grading system should consist of 4 or 5 categories. A 3-level system does not sufficiently discriminate, and with more than 5 categories the lowest levels are rarely used. Grades must be reported with clear information about their significance in each institution.

[Diagnostic approach to popliteal venous aneurysm]

Venous aneurysms are rare vascular abnormalities and are often described in patients presenting with pulmonary embolism. The occasional real time ultrasound examination of an aneurysm of venous system in the popliteal fossa has focalized our interest in the diagnostic approach of this entity. In our experience and in the literature the physical examination is usually negative while the ultrasound gives high quality imaging combined to a Doppler evaluation, so this kind of diagnostic tool is desirable as a first approach. Both morphology and flow hemodynamics can be detected in a non invasive way. About wall aspect and surrounding tissue is underlined the MRT and CT scanning, the thrombotic extension is well inspected. The venography is the definitive study and should always be performed because it is the most reliable examination and specific until the sac of aneurysm is filled from the contrast. However this diagnostic modality is useful in the patient undergoing surgical repair.

[The popliteal artery entrapment syndrome. Clinical experience]

The authors report their experience in treating three cases of popliteal artery entrapment. The analysis is based on the onset and the gap of time between the symptoms and the diagnostic certainty referred to the age of the patients. The diagnostic approach and follow-up is discussed including magnetic resonance of popliteal fossa. The surgical approach was constantly a shaped dorsal incision, and the reconstruction was performed in two cases with carbon coated dacron grafts of 6 mm diameter for the inadequacy of veins available. Any true aneurysm formation was identified. All grafts are patent on follow-up and the viability of the popliteal artery that underwent to simply myotomy is confirmed too by doppler ultrasound. Any recurrence of symptoms is recognized, in only one case was observed a concomitant entrapment in the other leg, not treated now is underlined. The advantage available for the patient in a physiokinetic therapy program, forerunner of a complete functional restoring, especially in athletic patients.

[A parotid arteriovenous fistula of nontraumatic origin. A case report]

The authors report their experience of a case of non traumatic arteriovenous communication of the parotid region in an adult subject. They confirm that its manifestations in grown-ups are to be linked with an inactive angiodysplastic field. The diagnostic approaches in the face of a hybrid symptomatology and the therapeutic choices are described. Moreover, an aesthetically and functionally efficient surgical correction is proposed.