Novel association of Dandy-Walker malformation with CAPN15 variants expands the phenotype of oculogastrointestinal neurodevelopmental syndrome
Beaman MM, Guidugli L, Hammer M, Barrows C, Gregor A, Lee S, Deak KL, McDonald MT, Jensen C, Zaki MS, Masri AT, Hobbs CA, Gleeson JG, Cohen JL.
Am J Med Genet A. 2023 Aug 19. doi: 10.1002/ajmg.a.63363. Online ahead of print.
Oculogastrointestinal neurodevelopmental syndrome has been described in seven previously published individuals who harbor biallelic pathogenic variants in the CAPN15 gene. Biallelic missense variants have been reported to demonstrate a phenotype of eye abnormalities and developmental delay, while biallelic loss of function variants exhibit phenotypes including microcephaly and craniofacial abnormalities, cardiac and genitourinary malformations, and abnormal neurologic activity. We report six individuals from three unrelated families harboring biallelic deleterious variants in CAPN15 with phenotypes overlapping those previously described for this disorder. Of the individuals affected, four demonstrate radiographic evidence of the classical triad of Dandy-Walker malformation including hypoplastic vermis, fourth ventricle enlargement, and torcular elevation. Cerebellar anomalies have not been previously reported in association with CAPN15-related disease. Here, we present three unrelated families with findings consistent with oculogastrointestinal neurodevelopmental syndrome and cerebellar pathology including Dandy-Walker malformation. To corroborate these novel clinical findings, we present supporting data from the mouse model suggesting an important role for this protein in normal cerebellar development. Our findings add six molecularly confirmed cases to the literature and additionally establish a new association of Dandy-Walker malformation with biallelic CAPN15 variants, thereby expanding the neurologic spectrum among patients affected by CAPN15-related disease.
August 19, 2023
Biallelic loss of function variants in WBP4 , encoding a spliceosome protein, result in a variable neurodevelopmental delay syndrome
Engal E, Oja KT, Maroofian R, Geminder O, Le TL, Mor E, Tzvi N, Elefant N, Zaki MS, Gleeson JG, Muru K, Pajusalu S, Wojcik MH, Pachat D, Elmaksoud MA, Jeong WC, Lee H, Bauer P, Zifarelli G, Houlden H, Elpeleg O, Gordon C, Harel T, Õunap K, Salton M, Mor-Shaked H.
medRxiv. 2023 Jun 27:2023.06.19.23291425. doi: 10.1101/2023.06.19.23291425. Preprint.
Over two dozen spliceosome proteins are involved in human diseases, also referred to as spliceosomopathies. WBP4 (WW Domain Binding Protein 4) is part of the early spliceosomal complex, and was not described before in the context of human pathologies. Ascertained through GeneMatcher we identified eleven patients from eight families, with a severe neurodevelopmental syndrome with variable manifestations. Clinical manifestations included hypotonia, global developmental delay, severe intellectual disability, brain abnormalities, musculoskeletal and gastrointestinal abnormalities. Genetic analysis revealed overall five different homozygous loss-of-function variants in WBP4 . Immunoblotting on fibroblasts from two affected individuals with different genetic variants demonstrated complete loss of protein, and RNA sequencing analysis uncovered shared abnormal splicing patterns, including enrichment for abnormalities of the nervous system and musculoskeletal system genes, suggesting that the overlapping differentially spliced genes are related to the common phenotypes of the probands. We conclude that biallelic variants in WBP4 cause a spliceosomopathy. Further functional studies are called for better understanding of the mechanism of pathogenicity.
June 27, 2023
BRAT1-related disorders: phenotypic spectrum and phenotype-genotype correlations from 97 patients
Engel C, Valence S, Delplancq G, Maroofian R, Accogli A, Agolini E, Alkuraya FS, Baglioni V, Bagnasco I, Becmeur-Lefebvre M, Bertini E, Borggraefe I, Brischoux-Boucher E, Bruel AL, Brusco A, Bubshait DK, Cabrol C, Cilio MR, Cornet MC, Coubes C, Danhaive O, Delague V, Denommé-Pichon AS, Di Giacomo MC, Doco-Fenzy M, Engels H, Cremer K, Gérard M, Gleeson JG, Heron D, Goffeney J, Guimier A, Harms FL, Houlden H, Iacomino M, Kaiyrzhanov R, Kamien B, Karimiani EG, Kraus D, Kuentz P, Kutsche K, Lederer D, Massingham L, Mignot C, Morris-Rosendahl D, Nagarajan L, Odent S, Ormières C, Partlow JN, Pasquier L, Penney L, Philippe C, Piccolo G, Poulton C, Putoux A, Rio M, Rougeot C, Salpietro V, Scheffer I, Schneider A, Srivastava S, Straussberg R, Striano P, Valente EM, Venot P, Villard L, Vitobello A, Wagner J, Wagner M, Zaki MS, Zara F, Lesca G, Yassaee VR, Miryounesi M, Hashemi-Gorji F, Beiraghi M, Ashrafzadeh F, Galehdari H, Walsh C, Novelli A, Tacke M, Sadykova D, Maidyrov Y, Koneev K, Shashkin C, Capra V, Zamani M, Van Maldergem L, Burglen L, Piard J.
Eur J Hum Genet. 2023 Jun 21. doi: 10.1038/s41431-023-01410-z. Online ahead of print.
BRAT1 biallelic variants are associated with rigidity and multifocal seizure syndrome, lethal neonatal (RMFSL), and neurodevelopmental disorder associating cerebellar atrophy with or without seizures syndrome (NEDCAS). To date, forty individuals have been reported in the literature. We collected clinical and molecular data from 57 additional cases allowing us to study a large cohort of 97 individuals and draw phenotype-genotype correlations. Fifty-nine individuals presented with BRAT1-related RMFSL phenotype. Most of them had no psychomotor acquisition (100%), epilepsy (100%), microcephaly (91%), limb rigidity (93%), and died prematurely (93%). Thirty-eight individuals presented a non-lethal phenotype of BRAT1-related NEDCAS phenotype. Seventy-six percent of the patients in this group were able to walk and 68% were able to say at least a few words. Most of them had cerebellar ataxia (82%), axial hypotonia (79%) and cerebellar atrophy (100%). Genotype-phenotype correlations in our cohort revealed that biallelic nonsense, frameshift or inframe deletion/insertion variants result in the severe BRAT1-related RMFSL phenotype (46/46; 100%). In contrast, genotypes with at least one missense were more likely associated with NEDCAS (28/34; 82%). The phenotype of patients carrying splice variants was variable: 41% presented with RMFSL (7/17) and 59% with NEDCAS (10/17).
June 21, 2023
AMFR dysfunction causes autosomal recessive spastic paraplegia in human that is amenable to statin treatment in a preclinical model
Deng R, Medico-Salsench E, Nikoncuk A, Ramakrishnan R, Lanko K, Kühn NA, van der Linde HC, Lor-Zade S, Albuainain F, Shi Y, Yousefi S, Capo I, van den Herik EM, van Slegtenhorst M, van Minkelen R, Geeven G, Mulder MT, Ruijter GJG, Lütjohann D, Jacobs EH, Houlden H, Pagnamenta AT, Metcalfe K, Jackson A, Banka S, De Simone L, Schwaede A, Kuntz N, Palculict TB, Abbas S, Umair M, AlMuhaizea M, Colak D, AlQudairy H, Alsagob M, Pereira C, Trunzo R, Karageorgou V, Bertoli-Avella AM, Bauer P, Bouman A, Hoefsloot LH, van Ham TJ, Issa M, Zaki MS, Gleeson JG, Willemsen R, Kaya N, Arold ST, Maroofian R, Sanderson LE, Barakat TS.
Acta Neuropathol. 2023 Apr 29. doi: 10.1007/s00401-023-02579-9. Online ahead of print.
Hereditary spastic paraplegias (HSP) are rare, inherited neurodegenerative or neurodevelopmental disorders that mainly present with lower limb spasticity and muscle weakness due to motor neuron dysfunction. Whole genome sequencing identified bi-allelic truncating variants in AMFR, encoding a RING-H2 finger E3 ubiquitin ligase anchored at the membrane of the endoplasmic reticulum (ER), in two previously genetically unexplained HSP-affected siblings. Subsequently, international collaboration recognized additional HSP-affected individuals with similar bi-allelic truncating AMFR variants, resulting in a cohort of 20 individuals from 8 unrelated, consanguineous families. Variants segregated with a phenotype of mainly pure but also complex HSP consisting of global developmental delay, mild intellectual disability, motor dysfunction, and progressive spasticity. Patient-derived fibroblasts, neural stem cells (NSCs), and in vivo zebrafish modeling were used to investigate pathomechanisms, including initial preclinical therapy assessment. The absence of AMFR disturbs lipid homeostasis, causing lipid droplet accumulation in NSCs and patient-derived fibroblasts which is rescued upon AMFR re-expression. Electron microscopy indicates ER morphology alterations in the absence of AMFR. Similar findings are seen in amfra-/- zebrafish larvae, in addition to altered touch-evoked escape response and defects in motor neuron branching, phenocopying the HSP observed in patients. Interestingly, administration of FDA-approved statins improves touch-evoked escape response and motor neuron branching defects in amfra-/- zebrafish larvae, suggesting potential therapeutic implications. Our genetic and functional studies identify bi-allelic truncating variants in AMFR as a cause of a novel autosomal recessive HSP by altering lipid metabolism, which may potentially be therapeutically modulated using precision medicine with statins.
April 29, 2023
Clinical and molecular spectrum of a large Egyptian cohort with ALS2-related disorders of infantile-onset of clinical continuum IAHSP/JPLS
Zaki MS, Sharaf-Eldin WE, Rafat K, Elbendary HM, Kamel M, Elkhateeb N, Noureldeen MM, Abdeltawab MA, Sadek AA, Essawi ML, Lau T, Murphy D, Abdel-Hamid MS, Holuden H, Issa MY, Gleeson JG.
Clin Genet. 2023 Apr 13. doi: 10.1111/cge.14338. Online ahead of print.
This study presents 46 patients from 23 unrelated Egyptian families with ALS2-related disorders without evidence of lower motor neuron involvement. Age at onset ranged from 10 months to 2.5 years, featuring progressive upper motor neuron signs. Detailed clinical phenotypes demonstrated inter- and intrafamilial variability. We identified 16 homozygous disease-causing ALS2 variants; sorted as splice-site, missense, frameshift, nonsense and in-frame in eight, seven, four, three, and one families, respectively. Seven of these variants were novel, expanding the mutational spectrum of the ALS2 gene. As expected, clinical severity was positively correlated with disease onset (p = 0.004). This work provides clinical and molecular profiles of a large single ethnic cohort of patients with ALS2 mutations, and suggests that infantile ascending hereditary spastic paralysis (IAHSP) and juvenile primary lateral sclerosis (JPLS) are belonged to one entity with no phenotype-genotype correlation.
April 13, 2023
TMEM161B modulates radial glial scaffolding in neocortical development
Wang L, Heffner C, Vong KL, Barrows C, Ha YJ, Lee S, Lara-Gonzalez P, Jhamb I, Van Der Meer D, Loughnan R, Parker N, Sievert D, Mittal S, Issa MY, Andreassen OA, Dale A, Dobyns WB, Zaki MS, Murray SA, Gleeson JG.
Proc Natl Acad Sci U S A. 2023 Jan 24;120(4):e2209983120. doi: 10.1073/pnas.2209983120. Epub 2023 Jan 20.
TMEM161B encodes an evolutionarily conserved widely expressed novel 8-pass transmembrane protein of unknown function in human. Here we identify TMEM161B homozygous hypomorphic missense variants in our recessive polymicrogyria (PMG) cohort. Patients carrying TMEM161B mutations exhibit striking neocortical PMG and intellectual disability. Tmem161b knockout mice fail to develop midline hemispheric cleavage, whereas knock-in of patient mutations and patient-derived brain organoids show defects in apical cell polarity and radial glial scaffolding. We found that TMEM161B modulates actin filopodia, functioning upstream of the Rho-GTPase CDC42. Our data link TMEM161B with human PMG, likely regulating radial glia apical polarity during neocortical development.
January 24, 2023
Stem Cell-Based Organoid Models of Neurodevelopmental Disorders
Wang L, Owusu-Hammond C, Sievert D, Gleeson JG.
Biol Psychiatry. 2023 Jan 24:S0006-3223(23)00039-2. doi: 10.1016/j.biopsych.2023.01.012. Online ahead of print.
The past decade has seen an explosion in the identification of genetic causes of neurodevelopmental disorders, including Mendelian, de novo, and somatic factors. These discoveries provide opportunities to understand cellular and molecular mechanisms as well as potential gene-gene and gene-environment interactions to support novel therapies. Stem cell-based models, particularly human brain organoids, can capture disease-associated alleles in the context of the human genome, engineered to mirror disease-relevant aspects of cellular complexity and developmental timing. These models have brought key insights into neurodevelopmental disorders as diverse as microcephaly, autism, and focal epilepsy. However, intrinsic organoid-to-organoid variability, low levels of certain brain-resident cell types, and long culture times required to reach maturity can impede progress. Several recent advances incorporate specific morphogen gradients, mixtures of diverse brain cell types, and organoid engraftment into animal models. Together with nonhuman primate organoid comparisons, mechanisms of human neurodevelopmental disorders are emerging.
January 24, 2023
Reversibility and developmental neuropathology of linear nevus sebaceous syndrome caused by dysregulation of the RAS pathway
Kim YE, Kim YS, Lee HE, So KH, Choe Y, Suh BC, Kim JH, Park SK, Mathern GW, Gleeson JG, Rah JC, Baek ST.
Cell Rep. 2023 Jan 14;42(1):112003. doi: 10.1016/j.celrep.2023.112003. Online ahead of print.
Linear nevus sebaceous syndrome (LNSS) is a neurocutaneous disorder caused by somatic gain-of-function mutations in KRAS or HRAS. LNSS brains have neurodevelopmental defects, including cerebral defects and epilepsy; however, its pathological mechanism and potentials for treatment are largely unclear. We show that introduction of KRASG12V in the developing mouse cortex results in subcortical nodular heterotopia and enhanced excitability, recapitulating major pathological manifestations of LNSS. Moreover, we show that decreased firing frequency of inhibitory neurons without KRASG12V expression leads to disrupted excitation and inhibition balance. Transcriptional profiling after destabilization domain-mediated clearance of KRASG12V in human neural progenitors and differentiating neurons identifies reversible functional networks underlying LNSS. Neurons expressing KRASG12V show molecular changes associated with delayed neuronal maturation, most of which are restored by KRASG12V clearance. These findings provide insights into the molecular networks underlying the reversibility of some of the neuropathologies observed in LNSS caused by dysregulation of the RAS pathway.
January 14, 2023
Comprehensive multi-omic profiling of somatic mutations in malformations of cortical development
Chung C, Yang X, Bae T, Vong KI, Mittal S, Donkels C, Westley Phillips H, Li Z, Marsh APL, Breuss MW, Ball LL, Garcia CAB, George RD, Gu J, Xu M, Barrows C, James KN, Stanley V, Nidhiry AS, Khoury S, Howe G, Riley E, Xu X, Copeland B, Wang Y, Kim SH, Kang HC, Schulze-Bonhage A, Haas CA, Urbach H, Prinz M, Limbrick DD Jr, Gurnett CA, Smyth MD, Sattar S, Nespeca M, Gonda DD, Imai K, Takahashi Y, Chen HH, Tsai JW, Conti V, Guerrini R, Devinsky O, Silva WA Jr, Machado HR, Mathern GW, Abyzov A, Baldassari S, Baulac S; Focal Cortical Dysplasia Neurogenetics Consortium; Brain Somatic Mosaicism Network; Gleeson JG.
Nat Genet. 2023 Jan 12. doi: 10.1038/s41588-022-01276-9. Online ahead of print.
Malformations of cortical development (MCD) are neurological conditions involving focal disruptions of cortical architecture and cellular organization that arise during embryogenesis, largely from somatic mosaic mutations, and cause intractable epilepsy. Identifying the genetic causes of MCD has been a challenge, as mutations remain at low allelic fractions in brain tissue resected to treat condition-related epilepsy. Here we report a genetic landscape from 283 brain resections, identifying 69 mutated genes through intensive profiling of somatic mutations, combining whole-exome and targeted-amplicon sequencing with functional validation including in utero electroporation of mice and single-nucleus RNA sequencing. Genotype-phenotype correlation analysis elucidated specific MCD gene sets associated with distinct pathophysiological and clinical phenotypes. The unique single-cell level spatiotemporal expression patterns of mutated genes in control and patient brains indicate critical roles in excitatory neurogenic pools during brain development and in promoting neuronal hyperexcitability after birth.
January 12, 2023
Control-independent mosaic single nucleotide variant detection with DeepMosaic
Yang X, Xu X, Breuss MW, Antaki D, Ball LL, Chung C, Shen J, Li C, George RD, Wang Y, Bae T, Cheng Y, Abyzov A, Wei L, Alexandrov LB, Sebat JL; NIMH Brain Somatic Mosaicism Network; Gleeson JG.
Nat Biotechnol. 2023 Jan 2. doi: 10.1038/s41587-022-01559-w. Online ahead of print.
Mosaic variants (MVs) reflect mutagenic processes during embryonic development and environmental exposure, accumulate with aging and underlie diseases such as cancer and autism. The detection of noncancer MVs has been computationally challenging due to the sparse representation of nonclonally expanded MVs. Here we present DeepMosaic, combining an image-based visualization module for single nucleotide MVs and a convolutional neural network-based classification module for control-independent MV detection. DeepMosaic was trained on 180,000 simulated or experimentally assessed MVs, and was benchmarked on 619,740 simulated MVs and 530 independent biologically tested MVs from 16 genomes and 181 exomes. DeepMosaic achieved higher accuracy compared with existing methods on biological data, with a sensitivity of 0.78, specificity of 0.83 and positive predictive value of 0.96 on noncancer whole-genome sequencing data, as well as doubling the validation rate over previous best-practice methods on noncancer whole-exome sequencing data (0.43 versus 0.18). DeepMosaic represents an accurate MV classifier for noncancer samples that can be implemented as an alternative or complement to existing methods.
January 2, 2023