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
A phenotypic spectrum of autism is attributable to the combined effects of rare variants, polygenic risk and sex
Antaki D, Guevara J, Maihofer AX, Klein M, Gujral M, Grove J, Carey CE, Hong O, Arranz MJ, Hervas A, Corsello C, Vaux KK, Muotri AR, Iakoucheva LM, Courchesne E, Pierce K, Gleeson JG, Robinson EB, Nievergelt CM, Sebat J.
Nat Genet. 2022 Jun 2. doi: 10.1038/s41588-022-01064-5. Online ahead of print.
The genetic etiology of autism spectrum disorder (ASD) is multifactorial, but how combinations of genetic factors determine risk is unclear. In a large family sample, we show that genetic loads of rare and polygenic risk are inversely correlated in cases and greater in females than in males, consistent with a liability threshold that differs by sex. De novo mutations (DNMs), rare inherited variants and polygenic scores were associated with various dimensions of symptom severity in children and parents. Parental age effects on risk for ASD in offspring were attributable to a combination of genetic mechanisms, including DNMs that accumulate in the paternal germline and inherited risk that influences behavior in parents. Genes implicated by rare variants were enriched in excitatory and inhibitory neurons compared with genes implicated by common variants. Our results suggest that a phenotypic spectrum of ASD is attributable to a spectrum of genetic factors that impact different neurodevelopmental processes.
June 2, 2022
Somatic mosaicism reveals clonal distributions of neocortical development
Breuss MW, Yang X, Schlachetzki JCM, Antaki D, Lana AJ, Xu X, Chung C, Chai G, Stanley V, Song Q, Newmeyer TF, Nguyen A, O’Brien S, Hoeksema MA, Cao B, Nott A, McEvoy-Venneri J, Pasillas MP, Barton ST, Copeland BR, Nahas S, Van Der Kraan L, Ding Y; NIMH Brain Somatic Mosaicism Network, Glass CK, Gleeson JG.
Nature. 2022 Apr 20. doi: 10.1038/s41586-022-04602-7. Online ahead of print.
The structure of the human neocortex underlies species-specific traits and reflects intricate developmental programs. Here we sought to reconstruct processes that occur during early development by sampling adult human tissues. We analysed neocortical clones in a post-mortem human brain through a comprehensive assessment of brain somatic mosaicism, acting as neutral lineage recorders1,2. We combined the sampling of 25 distinct anatomic locations with deep whole-genome sequencing in a neurotypical deceased individual and confirmed results with 5 samples collected from each of three additional donors. We identified 259 bona fide mosaic variants from the index case, then deconvolved distinct geographical, cell-type and clade organizations across the brain and other organs. We found that clones derived after the accumulation of 90-200 progenitors in the cerebral cortex tended to respect the midline axis, well before the anterior-posterior or ventral-dorsal axes, representing a secondary hierarchy following the overall patterning of forebrain and hindbrain domains. Clones across neocortically derived cells were consistent with a dual origin from both dorsal and ventral cellular populations, similar to rodents, whereas the microglia lineage appeared distinct from other resident brain cells. Our data provide a comprehensive analysis of brain somatic mosaicism across the neocortex and demonstrate cellular origins and progenitor distribution patterns within the human brain.
April 20, 2022
El-Hattab-Alkuraya syndrome caused by biallelic WDR45B pathogenic variants: further delineation of the phenotype and genotype
Almannai M, Marafi D, Abdel-Salam GMH, Zaki MS, Duan R, Calame D, Herman I, Levesque FSHA, Elbendary HM, Hegazy I, Chung WK, Kavus H, Saeidi K, Maroofian R, AlHashim A, Al-Otaibi A, Madhi AA, Aboalseood HM, Alasmari A, Houlden H, Gleeson JG, Hunter JV, Posey JE, Lupski JR, El-Hattab AW.
Clin Genet. 2022 Mar 23. doi: 10.1111/cge.14132. Online ahead of print.
Homozygous pathogenic variants in WDR45B were first identified in six subjects from three unrelated families with global development delay, refractory seizures, spastic quadriplegia, and brain malformations. Since the initial report in 2018, no further cases have been described. In this report, we present 12 additional individuals from seven unrelated families and their clinical, radiological, and molecular findings. Six different variants in WDR45B were identified, five of which are novel. Microcephaly and global developmental delay were observed in all subjects, and seizures and spastic quadriplegia in most. Common findings on brain imaging include cerebral atrophy, ex-vacuo ventricular dilatation, brainstem volume loss, and symmetric under-opercularization. El-Hattab-Alkuraya syndrome is associated with a consistent phenotype characterized by early onset cerebral atrophy resulting in microcephaly, developmental delay, spastic quadriplegia, and seizures. The phenotype appears to be more severe among individuals with loss-of-function variants whereas those with missense variants were less severely affected suggesting a potential genotype-phenotype correlation in this disorder. A brain imaging pattern emerges which is consistent among individuals with loss-of-function variants and could potentially alert the neuroradiologists or clinician to consider WDR45B-related El-Hattab-Alkuraya syndrome. This article is protected by copyright. All rights reserved.
March 23, 2022
Consolidation of the clinical and genetic definition of a SOX4-related neurodevelopmental syndrome
Angelozzi M, Karvande A, Molin AN, Ritter AL, Leonard JMM, Savatt JM, Douglass K, Myers SM, Grippa M, Tolchin D, Zackai E, Donoghue S, Hurst ACE, Descartes M, Smith K, Velasco D, Schmanski A, Crunk A, Tokita MJ, de Lange IM, van Gassen K, Robinson H, Guegan K, Suri M, Patel C, Bournez M, Faivre L, Tran-Mau-Them F, Baker J, Fabie N, Weaver K, Shillington A, Hopkin RJ, Barge-Schaapveld DQCM, Ruivenkamp CA, Bökenkamp R, Vergano S, Seco Moro MN, Díaz de Bustamante A, Misra VK, Kennelly K, Rogers C, Friedman J, Wigby KM, Lenberg J, Graziano C, Ahrens-Nicklas RC, Lefebvre V.
J Med Genet. 2022 Mar 1:jmedgenet-2021-108375. doi: 10.1136/jmedgenet-2021-108375. Epub ahead of print. PMID: 35232796.
Background: A neurodevelopmental syndrome was recently reported in four patients with SOX4 heterozygous missense variants in the high-mobility-group (HMG) DNA-binding domain. The present study aimed to consolidate clinical and genetic knowledge of this syndrome.
Methods: We newly identified 17 patients with SOX4 variants, predicted variant pathogenicity using in silico tests and in vitro functional assays and analysed the patients’ phenotypes.
Results: All variants were novel, distinct and heterozygous. Seven HMG-domain missense and five stop-gain variants were classified as pathogenic or likely pathogenic variant (L/PV) as they precluded SOX4 transcriptional activity in vitro. Five HMG-domain and non-HMG-domain missense variants were classified as of uncertain significance (VUS) due to negative results from functional tests. When known, inheritance was de novo or from a mosaic unaffected or non-mosaic affected parent for patients with L/PV, and from a non-mosaic asymptomatic or affected parent for patients with VUS. All patients had neurodevelopmental, neurological and dysmorphic features, and at least one cardiovascular, ophthalmological, musculoskeletal or other somatic anomaly. Patients with L/PV were overall more affected than patients with VUS. They resembled patients with other neurodevelopmental diseases, including the SOX11-related and Coffin-Siris (CSS) syndromes, but lacked the most specific features of CSS.
Conclusion: These findings consolidate evidence of a fairly non-specific neurodevelopmental syndrome due to SOX4 haploinsufficiency in neurogenesis and multiple other developmental processes.
PMID: 35232796 | DOI: 10.1136/jmedgenet-2021-108375
March 1, 2022
Genetic Neurologic DiseaseNeurogenomics
Oligonucleotide correction of an intronic TIMMDC1 variant in cells of patients with severe neurodegenerative disorder
Kumar R, Corbett MA, Smith NJC, Hock DH, Kikhtyak Z, Semcesen LN, Morimoto A, Lee S, Stroud DA, Gleeson JG, Haan EA, Gecz J.
NPJ Genom Med. 2022 Jan 28;7(1):9. doi: 10.1038/s41525-021-00277-7.
TIMMDC1 encodes the Translocase of Inner Mitochondrial Membrane Domain-Containing protein 1 (TIMMDC1) subunit of complex I of the electron transport chain responsible for ATP production. We studied a consanguineous family with two affected children, now deceased, who presented with failure to thrive in the early postnatal period, poor feeding, hypotonia, peripheral neuropathy and drug-resistant epilepsy. Genome sequencing data revealed a known, deep intronic pathogenic variant TIMMDC1 c.597-1340A>G, also present in gnomAD (~1/5000 frequency), that enhances aberrant splicing. Using RNA and protein analysis we show almost complete loss of TIMMDC1 protein and compromised mitochondrial complex I function. We have designed and applied two different splice-switching antisense oligonucleotides (SSO) to restore normal TIMMDC1 mRNA processing and protein levels in patients’ cells. Quantitative proteomics and real-time metabolic analysis of mitochondrial function on patient fibroblasts treated with SSOs showed restoration of complex I subunit abundance and function. SSO-mediated therapy of this inevitably fatal TIMMDC1 neurologic disorder is an attractive possibility.
January 28, 2022
Genotype-Phenotype Comparison in POGZ-Related Neurodevelopmental Disorders by Using Clinical Scoring
Nagy D, Verheyen S, Wigby KM, Borovikov A, Sharkov A, Slegesky V, Larson A, Fagerberg C, Brasch-Andersen C, Kibæk M, Bader I, Hernan R, High FA, Chung WK, Schieving JH, Behunova J, Smogavec M, Laccone F, Witsch-Baumgartner M, Zobel J, Duba HC, Weis D.
Genes (Basel). 2022 Jan 15;13(1):154. doi: 10.3390/genes13010154.
POGZ-related disorders (also known as White-Sutton syndrome) encompass a wide range of neurocognitive abnormalities and other accompanying anomalies. Disease severity varies widely among POGZ patients and studies investigating genotype-phenotype association are scarce. Therefore, our aim was to collect data on previously unreported POGZ patients and perform a large-scale phenotype-genotype comparison from published data. Overall, 117 POGZ patients’ genotype and phenotype data were included in the analysis, including 12 novel patients. A severity scoring system was developed for the comparison. Mild and severe phenotypes were compared with the types and location of the variants and the predicted presence or absence of nonsense-mediated RNA decay (NMD). Missense variants were more often associated with mild phenotypes (p = 0.0421) and truncating variants predicted to escape NMD presented with more severe phenotypes (p < 0.0001). Within this group, variants in the prolin-rich region of the POGZ protein were associated with the most severe phenotypes (p = 0.0004). Our study suggests that gain-of-function or dominant negative effect through escaping NMD and the location of the variants in the prolin-rich domain of the protein may play an important role in the severity of manifestations of POGZ-associated neurodevelopmental disorders.
January 15, 2022
Clinico-radiological features, molecular spectrum, and identification of prognostic factors in developmental and epileptic encephalopathy due to inosine triphosphate pyrophosphatase (ITPase) deficiency
Scala M, Wortmann SB, Kaya N, Stellingwerff MD, Pistorio A, Glamuzina E, van Karnebeek CD, Skrypnyk C, Iwanicka-Pronicka K, Piekutowska-Abramczuk D, Ciara E, Tort F, Sheidley B, Poduri A, Jayakar P, Jayakar A, Upadia J, Walano N, Haack TB, Prokisch H, Aldhalaan H, Karimiani EG, Yildiz Y, Ceylan AC, Santiago-Sim T, Dameron A, Yang H, Toosi MB, Ashrafzadeh F, Akhondian J, Imannezhad S, Mirzadeh HS, Maqbool S, Farid A, Al-Muhaizea MA, Alshwameen MO, Aldowsari L, Alsagob M, Alyousef A, AlMass R, AlHargan A, Alwadei AH, AlRasheed MM, Colak D, Alqudairy H, Khan S, Lines MA, García Cazorla MÁ, Ribes A, Morava E, Bibi F, Haider S, Ferla MP, Taylor JC, Alsaif HS, Firdous A, Hashem M, Shashkin C, Koneev K, Kaiyrzhanov R, Efthymiou S, Genomics QS, Schmitt-Mechelke T, Ziegler A, Issa MY, Elbendary HM, Striano P, Alkuraya FS, Zaki MS, Gleeson JG, Barakat TS, Bierau J, van der Knaap MS, Maroofian R, Houlden H.
Hum Mutat. 2022 Jan 6. doi: 10.1002/humu.24326. Online ahead of print.
Developmental and epileptic encephalopathy 35 (DEE 35) is a severe neurological condition caused by biallelic variants in ITPA, encoding inosine triphosphate pyrophosphatase, an essential enzyme in purine metabolism. We delineate the genotypic and phenotypic spectrum of DEE 35, analyzing possible predictors for adverse clinical outcomes. We investigated a cohort of 28 new patients and reviewed previously described cases, providing a comprehensive characterization of 40 subjects. Exome sequencing was performed to identify underlying ITPA pathogenic variants. Brain MRI (magnetic resonance imaging) scans were systematically analyzed to delineate the neuroradiological spectrum. Survival curves according to the Kaplan-Meier method and log-rank test were used to investigate outcome predictors in different subgroups of patients. We identified 18 distinct ITPA pathogenic variants, including 14 novel variants, and two deletions. All subjects showed profound developmental delay, microcephaly, and refractory epilepsy followed by neurodevelopmental regression. Brain MRI revision revealed a recurrent pattern of delayed myelination and restricted diffusion of early myelinating structures. Congenital microcephaly and cardiac involvement were statistically significant novel clinical predictors of adverse outcomes. We refined the molecular, clinical, and neuroradiological characterization of ITPase deficiency, and identified new clinical predictors which may have a potentially important impact on diagnosis, counseling, and follow-up of affected individuals.
January 6, 2022