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1.
Am J Hum Genet ; 105(2): 302-316, 2019 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-31256877

RESUMO

Members of a paralogous gene family in which variation in one gene is known to cause disease are eight times more likely to also be associated with human disease. Recent studies have elucidated DHX30 and DDX3X as genes for which pathogenic variant alleles are involved in neurodevelopmental disorders. We hypothesized that variants in paralogous genes encoding members of the DExD/H-box RNA helicase superfamily might also underlie developmental delay and/or intellectual disability (DD and/or ID) disease phenotypes. Here we describe 15 unrelated individuals who have DD and/or ID, central nervous system (CNS) dysfunction, vertebral anomalies, and dysmorphic features and were found to have probably damaging variants in DExD/H-box RNA helicase genes. In addition, these individuals exhibit a variety of other tissue and organ system involvement including ocular, outer ear, hearing, cardiac, and kidney tissues. Five individuals with homozygous (one), compound-heterozygous (two), or de novo (two) missense variants in DHX37 were identified by exome sequencing. We identified ten total individuals with missense variants in three other DDX/DHX paralogs: DHX16 (four individuals), DDX54 (three individuals), and DHX34 (three individuals). Most identified variants are rare, predicted to be damaging, and occur at conserved amino acid residues. Taken together, these 15 individuals implicate the DExD/H-box helicases in both dominantly and recessively inherited neurodevelopmental phenotypes and highlight the potential for more than one disease mechanism underlying these disorders.

2.
Genet Med ; 2019 Jun 14.
Artigo em Inglês | MEDLINE | ID: mdl-31197268

RESUMO

PURPOSE: Noninvasive prenatal screening (NIPS) using genome sequencing also reveals maternal copy-number variations (CNVs). Those CNVs can be clinically actionable or harmful to the fetus if inherited. CNVs in the DMD gene potentially causing dystrophinopathies are among the most commonly observed maternal CNVs. We present our experience with maternal DMD gene CNVs detected by NIPS. METHODS: We analyzed the data of maternal CNVs detected in the DMD gene revealed by NIPS. RESULTS: Of 26,123 NIPS analyses, 16 maternal CNVs in the DMD gene were detected (1/1632 pregnant women). Variant classification regarding pathogenicity and phenotypic severity was based on public databases, segregation analysis in the family, and prediction of the effect on the reading frame. Ten CNVs were classified as pathogenic, four as benign, and two remained unclassified. CONCLUSION: NIPS leverages CNV screening in the general population of pregnant women. We implemented a strategy for the interpretation and the return of maternal CNVs in the DMD gene detected by NIPS.

3.
Am J Hum Genet ; 104(5): 957-967, 2019 May 02.
Artigo em Inglês | MEDLINE | ID: mdl-31006512

RESUMO

Replicating the human genome efficiently and accurately is a daunting challenge involving the duplication of upward of three billion base pairs. At the core of the complex machinery that achieves this task are three members of the B family of DNA polymerases: DNA polymerases α, δ, and ε. Collectively these multimeric polymerases ensure DNA replication proceeds at optimal rates approaching 2 × 103 nucleotides/min with an error rate of less than one per million nucleotides polymerized. The majority of DNA replication of undamaged DNA is conducted by DNA polymerases δ and ε. The DNA polymerase α-primase complex performs limited synthesis to initiate the replication process, along with Okazaki-fragment synthesis on the discontinuous lagging strand. An increasing number of human disorders caused by defects in different components of the DNA-replication apparatus have been described to date. These are clinically diverse and involve a wide range of features, including variable combinations of growth delay, immunodeficiency, endocrine insufficiencies, lipodystrophy, and cancer predisposition. Here, by using various complementary approaches, including classical linkage analysis, targeted next-generation sequencing, and whole-exome sequencing, we describe distinct missense and splice-impacting mutations in POLA1 in five unrelated families presenting with an X-linked syndrome involving intellectual disability, proportionate short stature, microcephaly, and hypogonadism. POLA1 encodes the p180 catalytic subunit of DNA polymerase α-primase. A range of replicative impairments could be demonstrated in lymphoblastoid cell lines derived from affected individuals. Our findings describe the presentation of pathogenic mutations in a catalytic component of a B family DNA polymerase member, DNA polymerase α.

4.
Hum Mutat ; 40(8): 1013-1029, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31021519

RESUMO

SATB2-associated syndrome (SAS) is an autosomal dominant neurodevelopmental disorder caused by alterations in the SATB2 gene. Here we present a review of published pathogenic variants in the SATB2 gene to date and report 38 novel alterations found in 57 additional previously unreported individuals. Overall, we present a compilation of 120 unique variants identified in 155 unrelated families ranging from single nucleotide coding variants to genomic rearrangements distributed throughout the entire coding region of SATB2. Single nucleotide variants predicted to result in the occurrence of a premature stop codon were the most commonly seen (51/120 = 42.5%) followed by missense variants (31/120 = 25.8%). We review the rather limited functional characterization of pathogenic variants and discuss current understanding of the consequences of the different molecular alterations. We present an expansive phenotypic review along with novel genotype-phenotype correlations. Lastly, we discuss current knowledge of animal models and present future prospects. This review should help provide better guidance for the care of individuals diagnosed with SAS.

5.
Epilepsia ; 60(4): 689-706, 2019 04.
Artigo em Inglês | MEDLINE | ID: mdl-30866059

RESUMO

OBJECTIVE: Copy number variations (CNVs) represent a significant genetic risk for several neurodevelopmental disorders including epilepsy. As knowledge increases, reanalysis of existing data is essential. Reliable estimates of the contribution of CNVs to epilepsies from sizeable populations are not available. METHODS: We assembled a cohort of 1255 patients with preexisting array comparative genomic hybridization or single nucleotide polymorphism array based CNV data. All patients had "epilepsy plus," defined as epilepsy with comorbid features, including intellectual disability, psychiatric symptoms, and other neurological and nonneurological features. CNV classification was conducted using a systematic filtering workflow adapted to epilepsy. RESULTS: Of 1097 patients remaining after genetic data quality control, 120 individuals (10.9%) carried at least one autosomal CNV classified as pathogenic; 19 individuals (1.7%) carried at least one autosomal CNV classified as possibly pathogenic. Eleven patients (1%) carried more than one (possibly) pathogenic CNV. We identified CNVs covering recently reported (HNRNPU) or emerging (RORB) epilepsy genes, and further delineated the phenotype associated with mutations of these genes. Additional novel epilepsy candidate genes emerge from our study. Comparing phenotypic features of pathogenic CNV carriers to those of noncarriers of pathogenic CNVs, we show that patients with nonneurological comorbidities, especially dysmorphism, were more likely to carry pathogenic CNVs (odds ratio = 4.09, confidence interval = 2.51-6.68; P = 2.34 × 10-9 ). Meta-analysis including data from published control groups showed that the presence or absence of epilepsy did not affect the detected frequency of CNVs. SIGNIFICANCE: The use of a specifically adapted workflow enabled identification of pathogenic autosomal CNVs in 10.9% of patients with epilepsy plus, which rose to 12.7% when we also considered possibly pathogenic CNVs. Our data indicate that epilepsy with comorbid features should be considered an indication for patients to be selected for a diagnostic algorithm including CNV detection. Collaborative large-scale CNV reanalysis leads to novel declaration of pathogenicity in unexplained cases and can promote discovery of promising candidate epilepsy genes.

6.
BMC Med Genomics ; 11(1): 123, 2018 Dec 19.
Artigo em Inglês | MEDLINE | ID: mdl-30567555

RESUMO

BACKGROUND: The etiology of more than half of all patients with X-linked intellectual disability remains elusive, despite array-based comparative genomic hybridization, whole exome or genome sequencing. Since short read massive parallel sequencing approaches do not allow the detection of larger tandem repeat expansions, we hypothesized that such expansions could be a hidden cause of X-linked intellectual disability. METHODS: We selectively captured over 1800 tandem repeats on the X chromosome and characterized them by long read single molecule sequencing in 3 families with idiopathic X-linked intellectual disability. RESULTS: In male DNA samples, full tandem repeat length sequences were obtained for 88-93% of the targets and up to 99.6% of the repeats with a moderate guanine-cytosine content. Read length and analysis pipeline allow to detect cases of > 900 bp tandem repeat expansion. In one family, one repeat expansion co-occurs with down-regulation of the neighboring MIR222 gene. This gene has previously been implicated in intellectual disability and is apparently linked to FMR1 and NEFH overexpression associated with neurological disorders. CONCLUSIONS: This study demonstrates the power of single molecule sequencing to measure tandem repeat lengths and detect expansions, and suggests that tandem repeat mutations may be a hidden cause of X-linked intellectual disability.


Assuntos
Cromossomos Humanos X , Deficiência Intelectual/genética , Sequências de Repetição em Tandem/genética , Hibridização Genômica Comparativa , Ilhas de CpG , Proteína do X Frágil de Retardo Mental/genética , Proteína do X Frágil de Retardo Mental/metabolismo , Ligação Genética , Genótipo , Sequenciamento de Nucleotídeos em Larga Escala , Humanos , Deficiência Intelectual/diagnóstico , Masculino , MicroRNAs/genética , Proteínas de Neurofilamentos/genética , Proteínas de Neurofilamentos/metabolismo , Linhagem , Análise de Sequência de RNA
7.
Genet Med ; 2018 Aug 30.
Artigo em Inglês | MEDLINE | ID: mdl-30158690

RESUMO

PURPOSE: Defects in the cohesin pathway are associated with cohesinopathies, notably Cornelia de Lange syndrome (CdLS). We aimed to delineate pathogenic variants in known and candidate cohesinopathy genes from a clinical exome perspective. METHODS: We retrospectively studied patients referred for clinical exome sequencing (CES, N = 10,698). Patients with causative variants in novel or recently described cohesinopathy genes were enrolled for phenotypic characterization. RESULTS: Pathogenic or likely pathogenic single-nucleotide and insertion/deletion variants (SNVs/indels) were identified in established disease genes including NIPBL (N = 5), SMC1A (N = 14), SMC3 (N = 4), RAD21 (N = 2), and HDAC8 (N = 8). The phenotypes in this genetically defined cohort skew towards the mild end of CdLS spectrum as compared with phenotype-driven cohorts. Candidate or recently reported cohesinopathy genes were supported by de novo SNVs/indels in STAG1 (N = 3), STAG2 (N = 5), PDS5A (N = 1), and WAPL (N = 1), and one inherited SNV in PDS5A. We also identified copy-number deletions affecting STAG1 (two de novo, one of unknown inheritance) and STAG2 (one of unknown inheritance). Patients with STAG1 and STAG2 variants presented with overlapping features yet without characteristic facial features of CdLS. CONCLUSION: CES effectively identified disease-causing alleles at the mild end of the cohensinopathy spectrum and enabled characterization of candidate disease genes.

8.
Front Genet ; 9: 150, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-29868108

RESUMO

The fragile X syndrome arises from the FMR1 CGG expansion of a premutation (55-200 repeats) to a full mutation allele (>200 repeats) and is the most frequent cause of inherited X-linked intellectual disability. The risk for a premutation to expand to a full mutation allele depends on the repeat length and AGG triplets interrupting this repeat. In genetic counseling it is important to have information on both these parameters to provide an accurate risk estimate to women carrying a premutation allele and weighing up having children. For example, in case of a small risk a woman might opt for a natural pregnancy followed up by prenatal diagnosis while she might choose for preimplantation genetic diagnosis (PGD) if the risk is high. Unfortunately, the detection of AGG interruptions was previously hampered by technical difficulties complicating their use in diagnostics. Therefore we recently developed, validated and implemented a new methodology which uses long-read single-molecule sequencing to identify AGG interruptions in females with a FMR1 premutation. Here we report on the assets of AGG interruption detection by sequencing and the impact of implementing the assay on genetic counseling.

9.
Am J Hum Genet ; 102(5): 744-759, 2018 05 03.
Artigo em Inglês | MEDLINE | ID: mdl-29656859

RESUMO

RORα, the RAR-related orphan nuclear receptor alpha, is essential for cerebellar development. The spontaneous mutant mouse staggerer, with an ataxic gait caused by neurodegeneration of cerebellar Purkinje cells, was discovered two decades ago to result from homozygous intragenic Rora deletions. However, RORA mutations were hitherto undocumented in humans. Through a multi-centric collaboration, we identified three copy-number variant deletions (two de novo and one dominantly inherited in three generations), one de novo disrupting duplication, and nine de novo point mutations (three truncating, one canonical splice site, and five missense mutations) involving RORA in 16 individuals from 13 families with variable neurodevelopmental delay and intellectual disability (ID)-associated autistic features, cerebellar ataxia, and epilepsy. Consistent with the human and mouse data, disruption of the D. rerio ortholog, roraa, causes significant reduction in the size of the developing cerebellum. Systematic in vivo complementation studies showed that, whereas wild-type human RORA mRNA could complement the cerebellar pathology, missense variants had two distinct pathogenic mechanisms of either haploinsufficiency or a dominant toxic effect according to their localization in the ligand-binding or DNA-binding domains, respectively. This dichotomous direction of effect is likely relevant to the phenotype in humans: individuals with loss-of-function variants leading to haploinsufficiency show ID with autistic features, while individuals with de novo dominant toxic variants present with ID, ataxia, and cerebellar atrophy. Our combined genetic and functional data highlight the complex mutational landscape at the human RORA locus and suggest that dual mutational effects likely determine phenotypic outcome.

10.
Hum Mutat ; 39(7): 993-1001, 2018 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-29691940

RESUMO

Mutations in CASK cause a wide spectrum of phenotypes in humans ranging from mild X-linked intellectual disability to a severe microcephaly (MC) and pontocerebellar hypoplasia syndrome. Nevertheless, predicting pathogenicity and phenotypic consequences of novel CASK mutations through the exclusive consideration of genetic information and population-based data remains a challenge. Using whole exome sequencing, we identified four novel CASK mutations in individuals with syndromic MC. To understand the functional consequences of the different point mutations on the development of MC and cerebellar defects, we established a transient loss-of-function zebrafish model, and demonstrate recapitulation of relevant neuroanatomical phenotypes. Furthermore, we utilized in vivo complementation studies to demonstrate that the three point mutations confer a loss-of-function effect. This work endorses zebrafish as a tractable model to rapidly assess the effect of novel CASK variants on brain development.

11.
Prenat Diagn ; 38(4): 258-266, 2018 03.
Artigo em Inglês | MEDLINE | ID: mdl-29388226

RESUMO

OBJECTIVE: Non-invasive prenatal detection of aneuploidies can be achieved with high accuracy through sequencing of cell-free maternal plasma DNA in the maternal blood plasma. However, false positive and negative non-invasive prenatal testing (NIPT) results remain. Fetoplacental mosaicism is the main cause for false positive and false negative NIPT. We set out to develop a method to detect placental chromosomal mosaicism via genome-wide circulating cell-free maternal plasma DNA screening. METHOD: Aneuploidy detection was combined with fetal fraction determination to enable the detection of placental mosaicism. This pipeline was applied to whole genome sequencing data derived from 19 735 plasma samples. Following an abnormal NIPT, test results were validated by conventional invasive prenatal or postnatal genetic testing. RESULTS: Respectively 3.2% (5/154), 12.8% (5/39), and 13.3% (2/15) of trisomies 21, 18, and 13 were predicted and confirmed to be mosaic. The incidence of other, rare autosomal trisomies was ~0.3% (58/19,735), 45 of which were predicted to be mosaic. Twin pregnancies with discordant fetal genotypes were predicted and confirmed. CONCLUSION: This approach permits the non-invasive detection of fetal autosomal aneuploidies and identifies pregnancies with a high risk of fetoplacental mosaicism. Knowledge about the presence of chromosomal mosaicism in the placenta influences risk estimation, genetic counseling, and improves prenatal management.

12.
Eur J Med Genet ; 61(7): 376-383, 2018 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-29427787

RESUMO

We describe a patient with a de novo balanced translocation 46,XY,t(9; 13)(q31.2; q22.1) and autism spectrum disorder, intellectual disability, a metopic craniosynostosis, a corpus callosum dysgenesis and dysmorphic facial features, most notably ptosis. Breakpoint mapping was performed by means of targeted locus amplification (TLA) and sequencing, because conventional breakpoint mapping by means of fluorescent in situ hybridization and long-range PCR was hampered by a complex submicroscopic rearrangement. The translocation breakpoints directly affected the genes KLF12 (chromosome 13) and ZNF462 (chromosome 9). The latter gene was disrupted by multiple breakpoints, resulting in the loss of three fragments and a rearrangement of the remaining fragments. Therefore, haploinsufficiency of ZNF462 was assumed. Loss-of-function variants in ZNF462 have recently been published by Weiss et al. (2017) in a series of eight patients from six independent families delineating the ZNF462-associated phenotype. The latter closely matches with the clinical features of the current translocation patient. Besides, no direct evidence for an association of KLF12 to the phenotypic features was found. Therefore, we conclude that the phenotype of the current patient is mainly caused by the disruption of ZNF462. We present clinical data from birth to adulthood and data on the cognitive and behavioral profile of the current patient which may add to a more precise counseling and surveillance of development in young children with ZNF462 mutations. In addition, the current case illustrates that TLA is an efficient method for determining complex chromosomal breakpoints.


Assuntos
Anormalidades Múltiplas/genética , Transtorno do Espectro Autista/genética , Proteínas de Ligação a DNA/genética , Deficiência Intelectual/genética , Fatores de Transcrição Kruppel-Like/genética , Proteínas do Tecido Nervoso/genética , Fatores de Transcrição/genética , Adulto , Anormalidades Craniofaciais/genética , Deformidades do Pé/genética , Deformidades da Mão/genética , Haploinsuficiência , Humanos , Masculino , Translocação Genética , Adulto Jovem
13.
Hum Mol Genet ; 27(4): 589-600, 2018 02 15.
Artigo em Inglês | MEDLINE | ID: mdl-29267967

RESUMO

FRMPD4 (FERM and PDZ Domain Containing 4) is a neural scaffolding protein that interacts with PSD-95 to positively regulate dendritic spine morphogenesis, and with mGluR1/5 and Homer to regulate mGluR1/5 signaling. We report the genetic and functional characterization of 4 FRMPD4 deleterious mutations that cause a new X-linked intellectual disability (ID) syndrome. These mutations were found to be associated with ID in ten affected male patients from four unrelated families, following an apparent X-linked mode of inheritance. Mutations include deletion of an entire coding exon, a nonsense mutation, a frame-shift mutation resulting in premature termination of translation, and a missense mutation involving a highly conserved amino acid residue neighboring FRMPD4-FERM domain. Clinical features of these patients consisted of moderate to severe ID, language delay and seizures alongside with behavioral and/or psychiatric disturbances. In-depth functional studies showed that a frame-shift mutation, FRMPD4p.Cys618ValfsX8, results in a disruption of FRMPD4 binding with PSD-95 and HOMER1, and a failure to increase spine density in transfected hippocampal neurons. Behavioral studies of frmpd4-KO mice identified hippocampus-dependent spatial learning and memory deficits in Morris Water Maze test. These findings point to an important role of FRMPD4 in normal cognitive development and function in humans and mice, and support the hypothesis that FRMPD4 mutations cause ID by disrupting dendritic spine morphogenesis in glutamatergic neurons.

14.
Eur J Hum Genet ; 26(1): 54-63, 2018 01.
Artigo em Inglês | MEDLINE | ID: mdl-29209020

RESUMO

Genotype-first combined with reverse phenotyping has shown to be a powerful tool in human genetics, especially in the era of next generation sequencing. This combines the identification of individuals with mutations in the same gene and linking these to consistent (endo)phenotypes to establish disease causality. We have performed a MIP (molecular inversion probe)-based targeted re-sequencing study in 3,275 individuals with intellectual disability (ID) to facilitate a genotype-first approach for 24 genes previously implicated in ID.Combining our data with data from a publicly available database, we confirmed 11 of these 24 genes to be relevant for ID. Amongst these, PHIP was shown to have an enrichment of disruptive mutations in the individuals with ID (5 out of 3,275). Through international collaboration, we identified a total of 23 individuals with PHIP mutations and elucidated the associated phenotype. Remarkably, all 23 individuals had developmental delay/ID and the majority were overweight or obese. Other features comprised behavioral problems (hyperactivity, aggression, features of autism and/or mood disorder) and dysmorphisms (full eyebrows and/or synophrys, upturned nose, large ears and tapering fingers). Interestingly, PHIP encodes two protein-isoforms, PHIP/DCAF14 and NDRP, each involved in neurodevelopmental processes, including E3 ubiquitination and neuronal differentiation. Detailed genotype-phenotype analysis points towards haploinsufficiency of PHIP/DCAF14, and not NDRP, as the underlying cause of the phenotype.Thus, we demonstrated the use of large scale re-sequencing by MIPs, followed by reverse phenotyping, as a constructive approach to verify candidate disease genes and identify novel syndromes, highlighted by PHIP haploinsufficiency causing an ID-overweight syndrome.

15.
Am J Med Genet A ; 176(1): 209-213, 2018 01.
Artigo em Inglês | MEDLINE | ID: mdl-29130599

RESUMO

Over the past decade chromosomal microarray analysis (array CGH) has allowed the discovery of many novel disease-causing recurrent microdeletion and microduplication syndromes. Here we present three unrelated patients (2F; 1M) from three different countries, with developmental delay, intellectual disability, hypotonia, fatigue, and highly similar dysmorphic facial features. Shared facial features are a broad and wide forehead, similar shape of the eyes with long palpebral fissures, a bulbous tip of the nose and thick lips. Intellectual disabilities range from mild to severe. One female patient and the male patient were investigated in childhood for significant hypotonia thought to be suggestive of a neuromuscular disorder. The two female patients also show excessive fatigue with daytime somnolence. The patients carry overlapping, de novo microdeletions of chromosome 17q11.2, with sizes ranging from 0.97 to 1.18 Mb. The smallest region of overlap (SRO) between the three patients is 863 kb, and contains seven genes, five of which are predicted to exhibit haploinsufficiency (CDK5R1, PSMD11, RHOT1, SUZ12, ZNF207) although none has yet been associated with genetic syndromes. Of these five genes, the brain expressed CDK5R1 gene constitutes a good candidate for the developmental delay, while the RHOT1 gene, involved in mitochondrial trafficking, might underlie the hypotonia and the excessive fatigue.


Assuntos
Deleção Cromossômica , Cromossomos Humanos Par 17 , Estudos de Associação Genética , Fenótipo , Adolescente , Criança , Hibridização Genômica Comparativa , Facies , Fadiga/diagnóstico , Fadiga/genética , Feminino , Humanos , Lactente , Deficiência Intelectual/diagnóstico , Deficiência Intelectual/genética , Masculino , Hipotonia Muscular/diagnóstico , Hipotonia Muscular/genética
16.
Mol Syndromol ; 8(6): 282-293, 2017 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-29230157

RESUMO

STIL (SCL/TAL1 interrupting locus) is a core component of the centriole duplication process. STIL mutations have been associated with both autosomal recessive primary microcephaly (MCPH) and holoprosencephaly. In this report, we describe a family with multiple miscarriages and 2 terminations of pregnancy due to marked fetal microcephaly, delayed cortical gyrification, and dysgenesis of the corpus callosum. Whole exome sequencing allowed us to identify novel compound heterozygous mutations in STIL. The mutations lie, respectively, in the CPAP/CENPJ and the hsSAS6 interacting domains of STIL. M-phase synchronized amniocytes from both affected fetuses did not display an aberrant number of centrioles, as shown previously for either STIL-depleted or overexpressing cells. However, we observed an elongation of at least 1 centriole for each duplicated centrosome. These preliminary results may point to a novel mechanism causing MCPH and embryonic lethality in humans.

17.
Hum Mol Genet ; 26(23): 4699-4714, 2017 12 01.
Artigo em Inglês | MEDLINE | ID: mdl-28973667

RESUMO

Intellectual Disability is a common and heterogeneous disorder characterized by limitations in intellectual functioning and adaptive behaviour, whose molecular mechanisms remain largely unknown. Among the numerous genes found to be involved in the pathogenesis of intellectual disability, 10% are located on the X-chromosome. We identified a missense mutation (c.236 C > G; p.S79W) in the SYN1 gene coding for synapsin I in the MRX50 family, affected by non-syndromic X-linked intellectual disability. Synapsin I is a neuronal phosphoprotein involved in the regulation of neurotransmitter release and neuronal development. Several mutations in SYN1 have been identified in patients affected by epilepsy and/or autism. The S79W mutation segregates with the disease in the MRX50 family and all affected members display intellectual disability as sole clinical manifestation. At the protein level, the S79W Synapsin I mutation is located in the region of the B-domain involved in recognition of highly curved membranes. Expression of human S79W Synapsin I in Syn1 knockout hippocampal neurons causes aberrant accumulation of small clear vesicles in the soma, increased clustering of synaptic vesicles at presynaptic terminals and increased frequency of excitatory spontaneous release events. In addition, the presence of S79W Synapsin I strongly reduces the mobility of synaptic vesicles, with possible implications for the regulation of neurotransmitter release and synaptic plasticity. These results implicate SYN1 in the pathogenesis of non-syndromic intellectual disability, showing that alterations of synaptic vesicle trafficking are one possible cause of this disease, and suggest that distinct mutations in SYN1 may lead to distinct brain pathologies.


Assuntos
Retardo Mental Ligado ao Cromossomo X/genética , Mutação de Sentido Incorreto , Sinapsinas/genética , Vesículas Sinápticas/genética , Animais , Sequência de Bases , Humanos , Retardo Mental Ligado ao Cromossomo X/metabolismo , Camundongos , Camundongos Knockout , Mutação , Neurogênese/genética , Plasticidade Neuronal/genética , Neurônios/metabolismo , Linhagem , Terminações Pré-Sinápticas/metabolismo , Cultura Primária de Células , Transporte Proteico , Sinapsinas/metabolismo , Transmissão Sináptica/genética , Vesículas Sinápticas/metabolismo
18.
Invest Ophthalmol Vis Sci ; 58(12): 5485-5496, 2017 10 01.
Artigo em Inglês | MEDLINE | ID: mdl-29067402

RESUMO

Purpose: Optic nerve hypoplasia (ONH) is the most common cause of childhood congenital blindness in developed nations, yet the fundamental pathobiology of ONH remains unknown. The objective of this study was to employ a 'face validated' murine model to determine the timing of onset and the pathologic characteristics of ONH. Methods: Based on the robust linkage between X-linked CASK haploinsufficiency and clinically diagnosed ONH, we hypothesized that heterozygous deletion of CASK (CASK(+/-)) in rodents will produce an optic nerve pathology closely recapitulating ONH. We quantitatively analyzed the entire subcortical visual system in female CASK(+/-) mice using immunohistochemistry, anterograde axonal tracing, toluidine blue staining, transmission electron microscopy, and serial block-face scanning electron microscopy. Results: CASK haploinsuffiency in mice phenocopies human ONH with complete penetrance, thus satisfying the 'face validity'. We demonstrate that the optic nerve in CASK(+/-) mice is not only thin, but is comprised of atrophic retinal axons and displays reactive astrogliosis. Myelination of the optic nerve axons remains unchanged. Moreover, we demonstrate a significant decrease in retinal ganglion cell (RGC) numbers and perturbation in retinothalamic connectivity. Finally, we used this mouse model to define the onset and progression of ONH pathology, demonstrating for the first time that optic nerve defects arise at neonatally in CASK(+/-)mice. Conclusions: Optic nerve hypoplasia is a complex neuropathology of the subcortical visual system involving RGC loss, axonopathy, and synaptopathy and originates at a developmental stage in mice that corresponds to the late third trimester development in humans.


Assuntos
Doenças do Nervo Óptico/congênito , Nervo Óptico/patologia , Animais , Axônios/patologia , Modelos Animais de Doenças , Progressão da Doença , Guanilato Quinases/genética , Imuno-Histoquímica , Camundongos , Camundongos Endogâmicos C57BL , Mutação , Doenças do Nervo Óptico/genética , Doenças do Nervo Óptico/patologia , Células Ganglionares da Retina/patologia
19.
Hum Mutat ; 38(3): 324-331, 2017 03.
Artigo em Inglês | MEDLINE | ID: mdl-27883256

RESUMO

The FMR1 gene contains an unstable CGG repeat in its 5' untranslated region. Premutation alleles range between 55 and 200 repeat units and confer a risk for developing fragile X-associated tremor/ataxia syndrome or fragile X-associated primary ovarian insufficiency. Furthermore, the premutation allele often expands to a full mutation during female germline transmission giving rise to the fragile X syndrome. The risk for a premutation to expand depends mainly on the number of CGG units and the presence of AGG interruptions in the CGG repeat. Unfortunately, the detection of AGG interruptions is hampered by technical difficulties. Here, we demonstrate that single-molecule sequencing enables the determination of not only the repeat size, but also the complete repeat sequence including AGG interruptions in male and female alleles with repeats ranging from 45 to 100 CGG units. We envision this method will facilitate research and diagnostic analysis of the FMR1 repeat expansion.


Assuntos
Ataxia/genética , Proteína do X Frágil de Retardo Mental/genética , Síndrome do Cromossomo X Frágil/genética , Heterozigoto , Mutação , Tremor/genética , Expansão das Repetições de Trinucleotídeos , Ataxia/diagnóstico , Análise Mutacional de DNA , Feminino , Síndrome do Cromossomo X Frágil/diagnóstico , Humanos , Masculino , Tremor/diagnóstico , Repetições de Trinucleotídeos
20.
Genet Med ; 19(3): 306-313, 2017 03.
Artigo em Inglês | MEDLINE | ID: mdl-27584908

RESUMO

PURPOSE: Genome-wide sequencing of cell-free (cf)DNA of pregnant women aims to detect fetal chromosomal imbalances. Because the largest fraction of cfDNA consists of maternal rather than fetal DNA fragments, maternally derived copy-number variants (CNVs) are also measured. Despite their potential clinical relevance, current analyses do not interpret maternal CNVs. Here, we explore the accuracy and clinical value of maternal CNV analysis. METHODS: Noninvasive prenatal testing was performed by whole-genome shotgun sequencing on plasma samples. Following mapping of the sequencing reads, the landscape of maternal CNVs was charted for 9,882 women using SeqCBS analysis. Recurrent CNVs were validated retrospectively by comparing their incidence with published reports. Nonrecurrent CNVs were prospectively confirmed by array comparative genomic hybridization or fluorescent in situ hybridization analysis on maternal lymphocytes. RESULTS: Consistent with population estimates, 10% nonrecurrent and 0.4% susceptibility CNVs for low-penetrant genomic disorders were identified. Five clinically actionable variants were reported to the pregnant women, including haploinsufficiency of RUNX1, a mosaicism for segmental chromosome 13 deletion, an unbalanced translocation, and two interstitial chromosome X deletions. CONCLUSION: Shotgun sequencing of cfDNA not only enables the detection of fetal aneuploidies but also reveals the presence of maternal CNVs. Some of those variants are clinically actionable or could potentially be harmful for the fetus. Interrogating the maternal CNV landscape can improve overall pregnancy management, and we propose reporting those variants if clinically relevant. The identification and reporting of such CNVs pose novel counseling dilemmas that warrant further discussions and development of societal guidelines.Genet Med 19 3, 306-313.


Assuntos
Ácidos Nucleicos Livres/análise , Testes Genéticos/métodos , Diagnóstico Pré-Natal/métodos , Adulto , Aneuploidia , Ácidos Nucleicos Livres/genética , Aberrações Cromossômicas , Hibridização Genômica Comparativa , DNA/sangue , DNA/genética , Variações do Número de Cópias de DNA , Feminino , Feto , Sequenciamento de Nucleotídeos em Larga Escala/métodos , Humanos , Hibridização in Situ Fluorescente , Achados Incidentais , Gravidez , Estudos Retrospectivos , Análise de Sequência de DNA/métodos
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