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Neurobiology of Disease Sep 2023The vacuolar protein sorting-associated protein 13B (VPS13B) is a large and highly conserved protein. Disruption of VPS13B causes the autosomal recessive Cohen syndrome,...
The vacuolar protein sorting-associated protein 13B (VPS13B) is a large and highly conserved protein. Disruption of VPS13B causes the autosomal recessive Cohen syndrome, a rare disorder characterized by microcephaly and intellectual disability among other features, including developmental delay, hypotonia, and friendly-personality. However, the underlying mechanisms by which VPS13B disruption leads to brain dysfunction still remain unexplained. To gain insights into the neuropathogenesis of Cohen syndrome, we systematically characterized brain changes in Vps13b-mutant mice and compared murine findings to 235 previously published and 17 new patients diagnosed with VPS13B-related Cohen syndrome. We showed that Vps13b is differentially expressed across brain regions with the highest expression in the cerebellum, the hippocampus and the cortex with postnatal peak. Half of the Vps13b mice die during the first week of life. The remaining mice have a normal lifespan and display the core phenotypes of the human disease, including microcephaly, growth delay, hypotonia, altered memory, and enhanced sociability. Systematic 2D and 3D brain histo-morphological analyses reveal specific structural changes in the brain starting after birth. The dentate gyrus is the brain region with the most prominent reduction in size, while the motor cortex is specifically thinner in layer VI. The fornix, the fasciculus retroflexus, and the cingulate cortex remain unaffected. Interestingly, these neuroanatomical changes implicate an increase of neuronal death during infantile stages with no progression in adulthood suggesting that VPS13B promotes neuronal survival early in life. Importantly, whilst both sexes were affected, some neuroanatomical and behavioral phenotypes were less pronounced or even absent in females. We evaluate sex differences in Cohen patients and conclude that females are less affected both in mice and patients. Our findings provide new insights about the neurobiology of VPS13B and highlight previously unreported brain phenotypes while defining Cohen syndrome as a likely new entity of non-progressive infantile neurodegeneration.
Topics: Child; Humans; Male; Female; Animals; Mice; Microcephaly; Muscle Hypotonia; Retinal Degeneration; Developmental Disabilities; Phenotype
PubMed: 37573958
DOI: 10.1016/j.nbd.2023.106259 -
Proceedings of the National Academy of... Nov 2023In a forward genetic screen of mice with -ethyl--nitrosourea-induced mutations for aberrant immune function, we identified animals with low percentages of B220 cells in...
In a forward genetic screen of mice with -ethyl--nitrosourea-induced mutations for aberrant immune function, we identified animals with low percentages of B220 cells in the peripheral blood. The causative mutation was in , encoding immediate early response 3 interacting protein 1 (IER3IP1), an endoplasmic reticulum membrane protein mutated in an autosomal recessive neurodevelopmental disorder termed Microcephaly with simplified gyration, Epilepsy and permanent neonatal Diabetes Syndrome (MEDS) in humans. However, no immune function for IER3IP1 had previously been reported. The viable hypomorphic allele uncovered in this study, identical to a reported variant in a MEDS patient, reveals an essential hematopoietic-intrinsic role for IER3IP1 in B cell development and function. We show that IER3IP1 forms a complex with the Golgi transmembrane protein 167A and limits activation of the unfolded protein response mediated by inositol-requiring enzyme-1α and X-box binding protein 1 in B cells. Our findings suggest that B cell deficiency may be a feature of MEDS.
Topics: Humans; Animals; Mice; Membrane Proteins; Diabetes Mellitus; Mutation; Microcephaly; Epilepsy; Unfolded Protein Response
PubMed: 37934820
DOI: 10.1073/pnas.2312810120 -
BioRxiv : the Preprint Server For... Sep 2023Chromatin is a crucial regulator of gene expression and tightly controls development across species. Mutations in only one copy of multiple histone genes were identified...
Chromatin is a crucial regulator of gene expression and tightly controls development across species. Mutations in only one copy of multiple histone genes were identified in children with developmental disorders characterized by microcephaly, but their mechanistic roles in development remain unclear. Here we focus on dominant mutations affecting histone H4 lysine 91. These H4K91 mutants form aberrant nuclear puncta at specific heterochromatin regions. Mechanistically, H4K91 mutants demonstrate enhanced binding to the histone variant H3.3, and ablation of H3.3 or the H3.3-specific chaperone DAXX diminishes the mutant localization to chromatin. Our functional studies demonstrate that H4K91 mutant expression increases chromatin accessibility, alters developmental gene expression through accelerating pro-neural differentiation, and causes reduced mouse brain size , reminiscent of the microcephaly phenotypes of patients. Together, our studies unveil a distinct molecular pathogenic mechanism from other known histone mutants, where H4K91 mutants misregulate cell fate during development through abnormal genomic localization.
PubMed: 37808786
DOI: 10.1101/2023.09.29.560141 -
Science Translational Medicine Oct 2023Zika virus (ZIKV) is a mosquito-borne flavivirus that can vertically transmit from mother to fetus, potentially causing congenital defects, including microcephaly. It is...
Zika virus (ZIKV) is a mosquito-borne flavivirus that can vertically transmit from mother to fetus, potentially causing congenital defects, including microcephaly. It is not fully understood why some fetuses experience severe complications after in utero exposure to ZIKV, whereas others do not. Given the antigenic similarity between ZIKV and the closely related virus dengue (DENV) and the potential of DENV-specific antibodies to enhance ZIKV disease severity in mice, we questioned whether maternal DENV immunity could influence fetal outcomes in a nonhuman primate model of ZIKV vertical transmission. We found significantly increased severity of congenital Zika syndrome (CZS) in fetuses of DENV-immune cynomolgus macaques infected with ZIKV in early pregnancy compared with naïve controls, which occurred despite no effect on maternal ZIKV infection or antibody responses. Ultrasound measurements of head circumference and biparietal diameter measurements taken sequentially throughout pregnancy demonstrated CZS in fetuses of DENV-immune pregnant macaques. Furthermore, severe CZS enhanced by DENV immunity was typified by reduced cortical thickness and increased frequency of neuronal death, hemorrhaging, cellular infiltrations, calcifications, and lissencephaly in fetal brains. This study shows that maternal immunity to DENV can worsen ZIKV neurological outcomes in fetal primates, and it provides an animal model of vertical transmission closely approximating human developmental timelines that could be used to investigate severe ZIKV disease outcomes and interventions in fetuses.
Topics: Pregnancy; Humans; Female; Animals; Mice; Zika Virus; Zika Virus Infection; Microcephaly; Fetus; Dengue; Macaca; Antibodies, Viral
PubMed: 37878671
DOI: 10.1126/scitranslmed.add2420 -
Frontiers in Pediatrics 2023Mandibulo-Facial Dysostosis with Microcephaly (MFDM) is a rare disease with a broad spectrum of symptoms, characterized by zygomatic and mandibular hypoplasia,...
INTRODUCTION
Mandibulo-Facial Dysostosis with Microcephaly (MFDM) is a rare disease with a broad spectrum of symptoms, characterized by zygomatic and mandibular hypoplasia, microcephaly, and ear abnormalities. Here, we aimed at describing the external ear phenotype of MFDM patients, and train an Artificial Intelligence (AI)-based model to differentiate MFDM ears from non-syndromic control ears (binary classification), and from ears of the main differential diagnoses of this condition (multi-class classification): Treacher Collins (TC), Nager (NAFD) and CHARGE syndromes.
METHODS
The training set contained 1,592 ear photographs, corresponding to 550 patients. We extracted 48 patients completely independent of the training set, with only one photograph per ear per patient. After a CNN-(Convolutional Neural Network) based ear detection, the images were automatically landmarked. Generalized Procrustes Analysis was then performed, along with a dimension reduction using PCA (Principal Component Analysis). The principal components were used as inputs in an eXtreme Gradient Boosting (XGBoost) model, optimized using a 5-fold cross-validation. Finally, the model was tested on an independent validation set.
RESULTS
We trained the model on 1,592 ear photographs, corresponding to 1,296 control ears, 105 MFDM, 33 NAFD, 70 TC and 88 CHARGE syndrome ears. The model detected MFDM with an accuracy of 0.969 [0.838-0.999] ( < 0.001) and an AUC (Area Under the Curve) of 0.975 within controls (binary classification). Balanced accuracies were 0.811 [0.648-0.920] ( = 0.002) in a first multiclass design (MFDM vs. controls and differential diagnoses) and 0.813 [0.544-0.960] ( = 0.003) in a second multiclass design (MFDM vs. differential diagnoses).
CONCLUSION
This is the first AI-based syndrome detection model in dysmorphology based on the external ear, opening promising clinical applications both for local care and referral, and for expert centers.
PubMed: 37664547
DOI: 10.3389/fped.2023.1171277 -
Neurogenetics Jan 2024Sphingomyelin phosphodiesterase 4 (SMPD4) encodes a member of the Mg-dependent, neutral sphingomyelinase family that catalyzes the hydrolysis of the phosphodiester bond... (Review)
Review
Sphingomyelin phosphodiesterase 4 (SMPD4) encodes a member of the Mg-dependent, neutral sphingomyelinase family that catalyzes the hydrolysis of the phosphodiester bond of sphingomyelin to form phosphorylcholine and ceramide. Recent studies have revealed that biallelic loss-of-function variants of SMPD4 cause syndromic neurodevelopmental disorders characterized by microcephaly, congenital arthrogryposis, and structural brain anomalies. In this study, three novel loss-of-function SMPD4 variants were identified using exome sequencing (ES) in two independent patients with developmental delays, microcephaly, seizures, and brain structural abnormalities. Patient 1 had a homozygous c.740_741del, p.(Val247Glufs*21) variant and showed profound intellectual disability, hepatomegaly, a simplified gyral pattern, and a thin corpus callosum without congenital dysmorphic features. Patient 2 had a compound heterozygous nonsense c.2124_2125del, p.(Phe709*) variant and splice site c.1188+2dup variant. RNA analysis revealed that the c.1188+2dup variant caused exon 13 skipping, leading to a frameshift (p.Ala406Ser*6). In vitro transcription analysis using minigene system suggested that mRNA transcribed from mutant allele may be degraded by nonsense-mediated mRNA decay system. He exhibited diverse manifestations, including growth defects, muscle hypotonia, respiratory distress, arthrogryposis, insulin-dependent diabetes mellitus, sensorineural hearing loss, facial dysmorphism, and various brain abnormalities, including cerebral atrophy, hypomyelination, and cerebellar hypoplasia. Here, we review previous literatures and discuss the phenotypic diversity of SMPD4-related disorders.
Topics: Male; Humans; Microcephaly; Arthrogryposis; Neurodevelopmental Disorders; Nervous System Malformations; Intellectual Disability; Cerebellum
PubMed: 37882972
DOI: 10.1007/s10048-023-00737-5 -
Biotechnology and Bioengineering Feb 2024Brain organoids are self-organized, three-dimensional (3D) aggregates derived from pluripotent stem cells that have cell types and cellular architectures resembling... (Review)
Review
Brain organoids are self-organized, three-dimensional (3D) aggregates derived from pluripotent stem cells that have cell types and cellular architectures resembling those of the developing human brain. The current understanding of human brain developmental processes and neurological disorders has advanced significantly with the introduction of this in vitro model. Brain organoids serve as a translational link between two-dimensional (2D) cultures and in vivo models which imitate the neural tube formation at the early and late stages and the differentiation of neuroepithelium with whole-brain regionalization. In addition, the generation of region-specific brain organoids made it possible to investigate the pathogenic and etiological aspects of acquired and inherited brain disease along with drug discovery and drug toxicity testing. In this review article, we first summarize an overview of the existing methods and platforms used for generating brain organoids and their limitations and then discuss the recent advancement in brain organoid technology. In addition, we discuss how brain organoids have been used to model aspects of neurodevelopmental and neurodegenerative diseases, including autism spectrum disorder (ASD), Rett syndrome, Zika virus-related microcephaly, Alzheimer's disease (AD), Parkinson's disease (PD), and Huntington's disease (HD).
Topics: Humans; Autism Spectrum Disorder; Induced Pluripotent Stem Cells; Brain; Nervous System Diseases; Organoids; Zika Virus; Zika Virus Infection
PubMed: 38013504
DOI: 10.1002/bit.28606 -
Parkinsonism & Related Disorders Oct 2023Dystonia is a heterogeneous movement disorder involving various genetic backgrounds, and the implication of whole exome sequencing (WES) has yet to be clearly...
BACKGROUND
Dystonia is a heterogeneous movement disorder involving various genetic backgrounds, and the implication of whole exome sequencing (WES) has yet to be clearly elucidated. In this study, we performed WES in Korean patients with young-onset dystonia.
METHODS
We recruited patients with young-onset dystonia based on the new MDS dystonia classification at Samsung Medical Centre from 2015 to 2019. We excluded subjects diagnosed by single gene tests (GCH1, TOR1A, PANK2, PRRT2, and SGCE) or levodopa trials and subjects with focal or possible secondary dystonia. We performed WES in all enrolled subjects and confirmed the results with Sanger sequencing.
RESULTS
Of the 43 patients, we detected 11 disease-causing variants, classified as either pathogenic or likely pathogenic, in 9 patients (20.9%). Generalized dystonia, infancy-childhood-onset dystonia, and other combined neurologic manifestations were related with PV/LPV. When we retrospectively reviewed the patients with PV/LPV, brain imaging was diagnostic in 3 subjects (HTRA1, SCL20A, and WDR45), clinical characteristics of paroxysmal presentation were observed in 2 (ADCY5 and ATP1A3), and microcephaly was noted in 1 patient (KMT2B).
CONCLUSION
Clinical exome sequencing is helpful for the diagnosis of dystonia, especially for that with infancy-childhood onset, and generalized dystonia with other neurologic manifestations. Additionally, careful evaluations and examinations could provide information for selecting candidates for genetic testing.
Topics: Humans; Child; Dystonia; Exome Sequencing; Retrospective Studies; Dystonic Disorders; Genetic Testing; Mutation; Molecular Chaperones; Sodium-Potassium-Exchanging ATPase; Carrier Proteins
PubMed: 37607452
DOI: 10.1016/j.parkreldis.2023.105814 -
Clinical Genetics Sep 2023NAA20 is the catalytic subunit of the NatB complex, which is responsible for N-terminal acetylation of approximately 20% of the human proteome. Recently, pathogenic...
NAA20 is the catalytic subunit of the NatB complex, which is responsible for N-terminal acetylation of approximately 20% of the human proteome. Recently, pathogenic biallelic variants in NAA20 were associated with a novel neurodevelopmental disorder in five individuals with limited clinical information. We report two sisters harboring compound heterozygous variant (c.100C>T (p.Gln34Ter) and c.11T>C p.(Leu4Pro)) in the NAA20 gene, identified by exome sequencing. In vitro studies showed that the missense variant p.Leu4Pro resulted in a reduction of NAA20 catalytic activity due to weak coupling with the NatB auxiliary subunit. In addition, unpublished data of the previous families were reported, outlining the core phenotype of the NAA20-related disorder mostly characterized by cognitive impairment, microcephaly, ataxia, brain malformations, dysmorphism and variable occurrence of cardiac defect and epilepsy. Remarkably, our two patients featured epilepsy onset in adolescence suggesting this may be a part of syndrome evolution. Functional studies are needed to better understand the complexity of NAA20 variants pathogenesis as well as of other genes linked to N-terminal acetylation.
Topics: Adolescent; Humans; Catalytic Domain; Microcephaly; Syndrome; Nervous System Malformations; Phenotype; N-Terminal Acetyltransferase B
PubMed: 37191084
DOI: 10.1111/cge.14359 -
Molecular Cytogenetics Mar 2024Potocki-Lupski syndrome (PTLS, OMIM # 610883) is a rare genetic developmental disorder resulting from a partial heterozygous microduplication at chromosome 17p11.2. The...
BACKGROUND
Potocki-Lupski syndrome (PTLS, OMIM # 610883) is a rare genetic developmental disorder resulting from a partial heterozygous microduplication at chromosome 17p11.2. The condition is characterized by a wide variability of clinical expression, which can make its clinical and molecular diagnosis challenging.
CASE PRESENTATION
We report here a family (mother and her two children) diagnosed with PTLS. When examining children, neurological and psychological (neuropsychiatric) manifestations (speech delay, mild mental retardation), motor disorders, craniofacial dysmorphism (microcephaly, dolichocephaly, triangular face, wide bulging forehead, long chin, antimongoloid slant, "elfin" ears) were revealed. The suspected clinical diagnosis was confirmed by MLPA and CMA molecular genetic testing which revealed the presence of a segmental aneusomy; microduplication in the 17p11.2 region.
CONCLUSIONS
Children with PTLS can have a clinically recognizable and specific phenotype: craniofacial dysmorphism, motor and neurological manifestations, which may implicate a possible genetic disease to the attending physician. Moreover, each child with this syndrome is unique and may have a different clinical picture. The management of such patients requires a multidisciplinary team approach, including medical genetic counseling.
PubMed: 38519962
DOI: 10.1186/s13039-024-00673-5