Functional and clinical studies reveal pathophysiological complexity of CLCN4-related neurodevelopmental condition
Palmer EE, Pusch M, Picollo A, Forwood C, Nguyen MH, Suckow V, Gibbons J, Hoff A, Sigfrid L, Megarbane A, Nizon M, Cogné B, Beneteau C, Alkuraya FS, Chedrawi A, Hashem MO, Stamberger H, Weckhuysen S, Vanlander A, Ceulemans B, Rajagopalan S, Nunn K, Arpin S, Raynaud M, Motter CS, Ward-Melver C, Janssens K, Meuwissen M, Beysen D, Dikow N, Grimmel M, Haack TB, Clement E, McTague A, Hunt D, Townshend S, Ward M, Richards LJ, Simons C, Costain G, Dupuis L, Mendoza-Londono R, Dudding-Byth T, Boyle J, Saunders C, Fleming E, El Chehadeh S, Spitz MA, Piton A, Gerard B, Abi Warde MT, Rea G, McKenna C, Douzgou S, Banka S, Akman C, Bain JM, Sands TT, Wilson GN, Silvertooth EJ, Miller L, Lederer D, Sachdev R, Macintosh R, Monestier O, Karadurmus D, Collins F, Carter M, Rohena L, Willemsen MH, Ockeloen CW, Pfundt R, Kroft SD, Field M, Laranjeira FER, Fortuna AM, Soares AR, Michaud V, Naudion S, Golla S, Weaver DD, Bird LM, Friedman J, Clowes V, Joss S, Pölsler L, Campeau PM, Blazo M, Bijlsma EK, Rosenfeld JA, Beetz C, Powis Z, McWalter K, Brandt T, Torti E, Mathot M, Mohammad SS, Armstrong R, Kalscheuer VM.
Mol Psychiatry. 2022 Nov 16. doi: 10.1038/s41380-022-01852-9. Online ahead of print.
Missense and truncating variants in the X-chromosome-linked CLCN4 gene, resulting in reduced or complete loss-of-function (LOF) of the encoded chloride/proton exchanger ClC-4, were recently demonstrated to cause a neurocognitive phenotype in both males and females. Through international clinical matchmaking and interrogation of public variant databases we assembled a database of 90 rare CLCN4 missense variants in 90 families: 41 unique and 18 recurrent variants in 49 families. For 43 families, including 22 males and 33 females, we collated detailed clinical and segregation data. To confirm causality of variants and to obtain insight into disease mechanisms, we investigated the effect on electrophysiological properties of 59 of the variants in Xenopus oocytes using extended voltage and pH ranges. Detailed analyses revealed new pathophysiological mechanisms: 25% (15/59) of variants demonstrated LOF, characterized by a “shift” of the voltage-dependent activation to more positive voltages, and nine variants resulted in a toxic gain-of-function, associated with a disrupted gate allowing inward transport at negative voltages. Functional results were not always in line with in silico pathogenicity scores, highlighting the complexity of pathogenicity assessment for accurate genetic counselling. The complex neurocognitive and psychiatric manifestations of this condition, and hitherto under-recognized impacts on growth, gastrointestinal function, and motor control are discussed. Including published cases, we summarize features in 122 individuals from 67 families with CLCN4-related neurodevelopmental condition and suggest future research directions with the aim of improving the integrated care for individuals with this diagnosis.
November 16, 2022
Genetic Neurologic DiseaseNeurogenomics
Evaluating human mutation databases for “treatability” using patient-customized therapy
Mittal S, Tang I, Gleeson JG. Evaluating human mutation databases for “treatability” using patient-customized therapy. Med (N Y).
Med (N Y). 2022 Nov 11;3(11):740-759. doi: 10.1016/j.medj.2022.08.006.
Genome sequencing in the clinic often allows patients to receive a molecular diagnosis. However, variants are most often evaluated for pathogenicity, neglecting potential treatability and thus often yielding limited clinical benefit. Antisense oligonucleotides (ASOs), among others, offer attractive programmable and relatively safe platforms for customized therapy based upon the causative genetic variant. The landscape of ASO-treatable variants is largely uncharted, with new developments emerging for loss-of-function, haploinsufficient, and gain-of-function effects. ASOs can access the transcriptome to target splice-gain variants, poison exons, untranslated/regulatory regions, and naturally occurring antisense transcripts. Here we assess public variant databases and find that approximately half of pathogenic variants have one or more viable avenues for ASO therapy. The future might see medical teams considering “treatability” when interpreting genomic sequencing results to fully realize benefits for patients.
November 11, 2022
Brain monoamine vesicular transport disease caused by homozygous SLC18A2 variants: A study in 42 affected individuals
Saida K, Maroofian R, Sengoku T, Mitani T, Pagnamenta AT, Marafi D, Zaki MS, O’Brien TJ, Karimiani EG, Kaiyrzhanov R, Takizawa M, Ohori S, Leong HY, Akay G, Galehdari H, Zamani M, Romy R, Carroll CJ, Toosi MB, Ashrafzadeh F, Imannezhad S, Malek H, Ahangari N, Tomoum H, Gowda VK, Srinivasan VM, Murphy D, Dominik N, Elbendary HM, Rafat K, Yilmaz S, Kanmaz S, Serin M, Krishnakumar D, Gardham A, Maw A, Rao TS, Alsubhi S, Srour M, Buhas D, Jewett T, Goldberg RE, Shamseldin H, Frengen E, Misceo D, Strømme P, Magliocco Ceroni JR, Kim CA, Yesil G, Sengenc E, Guler S, Hull M, Parnes M, Aktas D, Anlar B, Bayram Y, Pehlivan D, Posey JE, Alavi S, Madani Manshadi SA, Alzaidan H, Al-Owain M, Alabdi L, Abdulwahab F, Sekiguchi F, Hamanaka K, Fujita A, Uchiyama Y, Mizuguchi T, Miyatake S, Miyake N, Elshafie RM, Salayev K, Guliyeva U, Alkuraya FS, Gleeson JG, Monaghan KG, Langley KG, Yang H, Motavaf M, Safari S, Alipour M, Ogata K, Brown AEX, Lupski JR, Houlden H, Matsumoto N.
Genet Med. 2022 Oct 31:S1098-3600(22)00948-0. doi: 10.1016/j.gim.2022.09.010. Online ahead of print.
PURPOSE: Brain monoamine vesicular transport disease is an infantile-onset movement disorder that mimics cerebral palsy. In 2013, the homozygous SLC18A2 variant, p.Pro387Leu, was first reported as a cause of this rare disorder, and dopamine agonists were efficient for treating affected individuals from a single large family. To date, only 6 variants have been reported. In this study, we evaluated genotype-phenotype correlations in individuals with biallelic SLC18A2 variants.
METHODS: A total of 42 affected individuals with homozygous SLC18A2 variant alleles were identified. We evaluated genotype-phenotype correlations and the missense variants in the affected individuals based on the structural modeling of rat VMAT2 encoded by Slc18a2, with cytoplasm- and lumen-facing conformations. A Caenorhabditis elegans model was created for functional studies.
RESULTS: A total of 19 homozygous SLC18A2 variants, including 3 recurrent variants, were identified using exome sequencing. The affected individuals typically showed global developmental delay, hypotonia, dystonia, oculogyric crisis, and autonomic nervous system involvement (temperature dysregulation/sweating, hypersalivation, and gastrointestinal dysmotility). Among the 58 affected individuals described to date, 16 (28%) died before the age of 13 years. Of the 17 patients with p.Pro237His, 9 died, whereas all 14 patients with p.Pro387Leu survived. Although a dopamine agonist mildly improved the disease symptoms in 18 of 21 patients (86%), some affected individuals with p.Ile43Phe and p.Pro387Leu showed milder phenotypes and presented prolonged survival even without treatment. The C. elegans model showed behavioral abnormalities.
CONCLUSION: These data expand the phenotypic and genotypic spectra of SLC18A2-related disorders.
October 31, 2022
Phenotypic continuum of NFU1-related disorders
Kaiyrzhanov R, Zaki MS, Lau T, Sen S, Azizimalamiri R, Zamani M, Sayin GY, Hilander T, Efthymiou S, Chelban V, Brown R, Thompson K, Scarano MI, Ganesh J, Koneev K, Gülaçar IM, Person R, Sadykova D, Maidyrov Y, Seifi T, Zadagali A, Bernard G, Allis K, Elloumi HZ, Lindy A, Taghiabadi E, Verma S, Logan R, Kirmse B, Bai R, Khalaf SM, Abdel-Hamid MS, Sedaghat A, Shariati G, Issa M, Zeighami J, Elbendary HM, Brown G, Taylor RW, Galehdari H, Gleeson JJ, Carroll CJ, Cowan JA, Moreno-De-Luca A, Houlden H, Maroofian R.
Ann Clin Transl Neurol. 2022 Oct 18. doi: 10.1002/acn3.51679. Online ahead of print.
Bi-allelic variants in Iron-Sulfur Cluster Scaffold (NFU1) have previously been associated with multiple mitochondrial dysfunctions syndrome 1 (MMDS1) characterized by early-onset rapidly fatal leukoencephalopathy. We report 19 affected individuals from 10 independent families with ultra-rare bi-allelic NFU1 missense variants associated with a spectrum of early-onset pure to complex hereditary spastic paraplegia (HSP) phenotype with a longer survival (16/19) on one end and neurodevelopmental delay with severe hypotonia (3/19) on the other. Reversible or irreversible neurological decompensation after a febrile illness was common in the cohort, and there were invariable white matter abnormalities on neuroimaging. The study suggests that MMDS1 and HSP could be the two ends of the NFU1-related phenotypic continuum.
October 18, 2022
Bi-allelic loss-of-function variants in TMEM147 cause moderate to profound intellectual disability with facial dysmorphism and pseudo-Pelger-Huët anomaly
Thomas Q, Motta M, Gautier T, Zaki MS, Ciolfi A, Paccaud J, Girodon F, Boespflug-Tanguy O, Besnard T, Kerkhof J, McConkey H, Masson A, Denommé-Pichon AS, Cogné B, Trochu E, Vignard V, El It F, Rodan LH, Alkhateeb MA, Jamra RA, Duplomb L, Tisserant E, Duffourd Y, Bruel AL, Jackson A, Banka S, McEntagart M, Saggar A, Gleeson JG, Sievert D, Bae H, Lee BH, Kwon K, Seo GH, Lee H, Saeed A, Anjum N, Cheema H, Alawbathani S, Khan I, Pinto-Basto J, Teoh J, Wong J, Sahari UBM, Houlden H, Zhelcheska K, Pannetier M, Awad MA, Lesieur-Sebellin M, Barcia G, Amiel J, Delanne J, Philippe C, Faivre L, Odent S, Bertoli-Avella A, Thauvin C, Sadikovic B, Reversade B, Maroofian R, Govin J, Tartaglia M, Vitobello A.
Am J Hum Genet. 2022 Aug 23:S0002-9297(22)00360-3. doi: 10.1016/j.ajhg.2022.08.008. Online ahead of print.
The transmembrane protein TMEM147 has a dual function: first at the nuclear envelope, where it anchors lamin B receptor (LBR) to the inner membrane, and second at the endoplasmic reticulum (ER), where it facilitates the translation of nascent polypeptides within the ribosome-bound TMCO1 translocon complex. Through international data sharing, we identified 23 individuals from 15 unrelated families with bi-allelic TMEM147 loss-of-function variants, including splice-site, nonsense, frameshift, and missense variants. These affected children displayed congruent clinical features including coarse facies, developmental delay, intellectual disability, and behavioral problems. In silico structural analyses predicted disruptive consequences of the identified amino acid substitutions on translocon complex assembly and/or function, and in vitro analyses documented accelerated protein degradation via the autophagy-lysosomal-mediated pathway. Furthermore, TMEM147-deficient cells showed CKAP4 (CLIMP-63) and RTN4 (NOGO) upregulation with a concomitant reorientation of the ER, which was also witnessed in primary fibroblast cell culture. LBR mislocalization and nuclear segmentation was observed in primary fibroblast cells. Abnormal nuclear segmentation and chromatin compaction were also observed in approximately 20% of neutrophils, indicating the presence of a pseudo-Pelger-Huët anomaly. Finally, co-expression analysis revealed significant correlation with neurodevelopmental genes in the brain, further supporting a role of TMEM147 in neurodevelopment. Our findings provide clinical, genetic, and functional evidence that bi-allelic loss-of-function variants in TMEM147 cause syndromic intellectual disability due to ER-translocon and nuclear organization dysfunction.
August 23, 2022
Analysis of somatic mutations in 131 human brains reveals aging-associated hypermutability
Bae T, Fasching L, Wang Y, Shin JH, Suvakov M, Jang Y, Norton S, Dias C, Mariani J, Jourdon A, Wu F, Panda A, Pattni R, Chahine Y, Yeh R, Roberts RC, Huttner A, Kleinman JE, Hyde TM, Straub RE, Walsh CA; Brain Somatic Mosaicism Network§, Urban AE, Leckman JF, Weinberger DR, Vaccarino FM, Abyzov A, Walsh CA, Park PJ, Sestan N, Weinberger D, Moran JV, Gage FH, Vaccarino FM, Gleeson J, Mathern G, Courchesne E, Roy S, Chess AJ, Akbarian S, Bizzotto S, Coulter M, Dias C, D’Gama A, Ganz J, Hill R, Huang AY, Khoshkhoo S, Kim S, Lee A, Lodato M, Maury EA, Miller M, Borges-Monroy R, Rodin R, Zhou Z, Bohrson C, Chu C, Cortes-Ciriano I, Dou Y, Galor A, Gulhan D, Kwon M, Luquette J, Sherman M, Viswanadham V, Jones A, Rosenbluh C, Cho S, Langmead B, Thorpe J, Erwin J, Jaffe A, McConnell M, Narurkar R, Paquola A, Shin J, Straub R, Abyzov A, Bae T, Jang Y, Wang Y, Molitor C, Peters M, Linker S, Reed P, Wang M, Urban A, Zhou B, Zhu X, Pattni R, Serres Amero A, Juan D, Lobon I, Marques-Bonet T, Solis Moruno M, Garcia Perez R, Povolotskaya I, Soriano E, Antaki D, Averbuj D, Ball L, Breuss M, Yang X, Chung C, Emery SB, Flasch DA, Kidd JM, Kopera HC, Kwan KY, Mills RE, Moldovan JB, Sun C, Zhao X, Zhou W, Frisbie TJ, Cherskov A, Fasching L, Jourdon A, Pochareddy S, Scuderi S.
Science. 2022 Jul 29;377(6605):511-517. doi: 10.1126/science.abm6222. Epub 2022 Jul 28.
We analyzed 131 human brains (44 neurotypical, 19 with Tourette syndrome, 9 with schizophrenia, and 59 with autism) for somatic mutations after whole genome sequencing to a depth of more than 200×. Typically, brains had 20 to 60 detectable single-nucleotide mutations, but ~6% of brains harbored hundreds of somatic mutations. Hypermutability was associated with age and damaging mutations in genes implicated in cancers and, in some brains, reflected in vivo clonal expansions. Somatic duplications, likely arising during development, were found in ~5% of normal and diseased brains, reflecting background mutagenesis. Brains with autism were associated with mutations creating putative transcription factor binding motifs in enhancer-like regions in the developing brain. The top-ranked affected motifs corresponded to MEIS (myeloid ectopic viral integration site) transcription factors, suggesting a potential link between their involvement in gene regulation and autism.
July 29, 2022
Bi-allelic loss-of-function variants in PPFIBP1 cause a neurodevelopmental disorder with microcephaly, epilepsy, and periventricular calcifications
Rosenhahn E, O’Brien TJ, Zaki MS, Sorge I, Wieczorek D, Rostasy K, Vitobello A, Nambot S, Alkuraya FS, Hashem MO, Alhashem A, Tabarki B, Alamri AS, Al Safar AH, Bubshait DK, Alahmady NF, Gleeson JG, Abdel-Hamid MS, Lesko N, Ygberg S, Correia SP, Wredenberg A, Alavi S, Seyedhassani SM, Ebrahimi Nasab M, Hussien H, Omar TEI, Harzallah I, Touraine R, Tajsharghi H, Morsy H, Houlden H, Shahrooei M, Ghavideldarestani M, Abdel-Salam GMH, Torella A, Zanobio M, Terrone G, Brunetti-Pierri N, Omrani A, Hentschel J, Lemke JR, Sticht H, Abou Jamra R, Brown AEX, Maroofian R, Platzer K.
Am J Hum Genet. 2022 Jul 7:S0002-9297(22)00261-0. doi: 10.1016/j.ajhg.2022.06.008. Online ahead of print.
PPFIBP1 encodes for the liprin-β1 protein, which has been shown to play a role in neuronal outgrowth and synapse formation in Drosophila melanogaster. By exome and genome sequencing, we detected nine ultra-rare homozygous loss-of-function variants in 16 individuals from 12 unrelated families. The individuals presented with moderate to profound developmental delay, often refractory early-onset epilepsy, and progressive microcephaly. Further common clinical findings included muscular hyper- and hypotonia, spasticity, failure to thrive and short stature, feeding difficulties, impaired vision, and congenital heart defects. Neuroimaging revealed abnormalities of brain morphology with leukoencephalopathy, ventriculomegaly, cortical abnormalities, and intracranial periventricular calcifications as major features. In a fetus with intracranial calcifications, we identified a rare homozygous missense variant that by structural analysis was predicted to disturb the topology of the SAM domain region that is essential for protein-protein interaction. For further insight into the effects of PPFIBP1 loss of function, we performed automated behavioral phenotyping of a Caenorhabditis elegans PPFIBP1/hlb-1 knockout model, which revealed defects in spontaneous and light-induced behavior and confirmed resistance to the acetylcholinesterase inhibitor aldicarb, suggesting a defect in the neuronal presynaptic zone. In conclusion, we establish bi-allelic loss-of-function variants in PPFIBP1 as a cause of an autosomal recessive severe neurodevelopmental disorder with early-onset epilepsy, microcephaly, and periventricular calcifications.
July 7, 2022
Unbiased mosaic variant assessment in sperm: a cohort study to test predictability of transmission
Breuss MW, Yang X, Stanley V, McEvoy-Venneri J, Xu X, Morales AJ, Gleeson JG.
Elife. 2022 Jul 5;11:e78459. doi: 10.7554/eLife.78459.
BACKGROUND: De novo mutations underlie individually rare but collectively common pediatric congenital disorders. Some of these mutations can also be detected in tissues and from cells in a parent, where their abundance and tissue distribution can be measured. We previously reported that a subset of these mutations is detectable in sperm from the father, predicted to impact the health of offspring.
METHODS: As a cohort study, in three independent couples undergoing in vitro fertilization, we first identified male gonadal mosaicism through deep whole genome sequencing. We then confirmed variants and assessed their transmission to preimplantation blastocysts (32 total) through targeted ultra-deep genotyping.
RESULTS: Across 55 gonadal mosaic variants, 15 were transmitted to blastocysts for a total of 19 transmission events. This represented an overall predictable but slight undertransmission based upon the measured mutational abundance in sperm. We replicated this conclusion in an independent, previously published family-based cohort.
CONCLUSIONS: Unbiased preimplantation genetic testing for gonadal mosaicism may represent a feasible approach to reduce the transmission of potentially harmful de novo mutations. This-in turn-could help to reduce their impact on miscarriages and pediatric disease.
FUNDING: No external funding was received for this work.
July 5, 2022
Monoallelic and biallelic mutations in RELN underlie a graded series of neurodevelopmental disorders
Di Donato N, Guerrini R, Billington CJ, Barkovich AJ, Dinkel P, Freri E, Heide M, Gershon ES, Gertler TS, Hopkin RJ, Jacob S, Keedy SK, Kooshavar D, Lockhart PJ, Lohmann DR, Mahmoud IG, Parrini E, Schrock E, Severi G, Timms AE, Webster RI, Willis MJH, Zaki MS, Gleeson JG, Leventer RJ, Dobyns WB.
Brain. 2022 Jun 30:awac164. doi: 10.1093/brain/awac164. Online ahead of print.
Reelin, a large extracellular protein, plays several critical roles in brain development and function. It is encoded by RELN, first identified as the gene disrupted in the reeler mouse, a classic neurological mutant exhibiting ataxia, tremors and a ‘reeling’ gait. In humans, biallelic variants in RELN have been associated with a recessive lissencephaly variant with cerebellar hypoplasia, which matches well with the homozygous mouse mutant that has abnormal cortical structure, small hippocampi and severe cerebellar hypoplasia. Despite the large size of the gene, only 11 individuals with RELN-related lissencephaly with cerebellar hypoplasia from six families have previously been reported. Heterozygous carriers in these families were briefly reported as unaffected, although putative loss-of-function variants are practically absent in the population (probability of loss of function intolerance = 1). Here we present data on seven individuals from four families with biallelic and 13 individuals from seven families with monoallelic (heterozygous) variants of RELN and frontotemporal or temporal-predominant lissencephaly variant. Some individuals with monoallelic variants have moderate frontotemporal lissencephaly, but with normal cerebellar structure and intellectual disability with severe behavioural dysfunction. However, one adult had abnormal MRI with normal intelligence and neurological profile. Thorough literature analysis supports a causal role for monoallelic RELN variants in four seemingly distinct phenotypes including frontotemporal lissencephaly, epilepsy, autism and probably schizophrenia. Notably, we observed a significantly higher proportion of loss-of-function variants in the biallelic compared to the monoallelic cohort, where the variant spectrum included missense and splice-site variants. We assessed the impact of two canonical splice-site variants observed as biallelic or monoallelic variants in individuals with moderately affected or normal cerebellum and demonstrated exon skipping causing in-frame loss of 46 or 52 amino acids in the central RELN domain. Previously reported functional studies demonstrated severe reduction in overall RELN secretion caused by heterozygous missense variants p.Cys539Arg and p.Arg3207Cys associated with lissencephaly suggesting a dominant-negative effect. We conclude that biallelic variants resulting in complete absence of RELN expression are associated with a consistent and severe phenotype that includes cerebellar hypoplasia. However, reduced expression of RELN remains sufficient to maintain nearly normal cerebellar structure. Monoallelic variants are associated with incomplete penetrance and variable expressivity even within the same family and may have dominant-negative effects. Reduced RELN secretion in heterozygous individuals affects only cortical structure whereas the cerebellum remains intact. Our data expand the spectrum of RELN-related neurodevelopmental disorders ranging from lethal brain malformations to adult phenotypes with normal brain imaging.
June 30, 2022
Endocannabinoid dysfunction in neurological disease: neuro-ocular DAGLA-related syndrome (NODRS)
Bainbridge MN, Mazumder A, Ogasawara D, Abou Jamra R, Bernard G, Bertini E, Burglen L, Cope H, Crawford A, Derksen A, Dure L, Gantz E, Koch-Hogrebe M, Hurst ACE, Mahida S, Marshall P, Micalizzi A, Novelli A, Peng H, Rodriguez D, Robbins SL, Rutledge SL, Scalise R, Schließke S, Shashi V, Srivastava S, Thiffault I, Topol S; Undiagnosed Disease Network, Qebibo L, Wieczorek D, Cravatt B, Haricharan S, Torkamani A, Friedman J.
Brain. 2022 Jun 23:awac223. doi: 10.1093/brain/awac223. Online ahead of print.
The endocannabinoid system is a highly conserved and ubiquitous signaling pathway with broad ranging effects. Despite critical pathway functions, gene variants have not previously been conclusively linked to human disease. We identified nine children from eight families with heterozygous, de novo truncating variants in the last exon of DAGLA with a neuro-ocular phenotype characterized by developmental delay, ataxia, and complex oculomotor abnormality. All children displayed paroxysms of nystagmus or eye deviation accompanied by compensatory head posture and worsened incoordination most frequently after waking. RNAseq showed clear expression of the truncated transcript and no differences were found between mutant and wild type DAGLA activity. Immunofluorescence staining of patient-derived fibroblasts and HEK cells expressing the mutant protein showed distinct perinuclear aggregation not detected in control samples. This report establishes truncating variants in the last DAGLA exon as the cause of a unique pediatric syndrome. Because enzymatic activity was preserved, the observed mis-localization of the truncated protein may account for the observed phenotype. Potential mechanisms include DAGLA haploinsufficiency at the plasma membrane or dominant negative effect. To our knowledge, this is the first report directly linking an endocannabinoid system component with human genetic disease and sets the stage for potential future therapeutic avenues.
June 23, 2022