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1.
Am J Hum Genet ; 111(4): 761-777, 2024 Apr 04.
Artigo em Inglês | MEDLINE | ID: mdl-38503299

RESUMO

Ion channels mediate voltage fluxes or action potentials that are central to the functioning of excitable cells such as neurons. The KCNB family of voltage-gated potassium channels (Kv) consists of two members (KCNB1 and KCNB2) encoded by KCNB1 and KCNB2, respectively. These channels are major contributors to delayed rectifier potassium currents arising from the neuronal soma which modulate overall excitability of neurons. In this study, we identified several mono-allelic pathogenic missense variants in KCNB2, in individuals with a neurodevelopmental syndrome with epilepsy and autism in some individuals. Recurrent dysmorphisms included a broad forehead, synophrys, and digital anomalies. Additionally, we selected three variants where genetic transmission has not been assessed, from two epilepsy studies, for inclusion in our experiments. We characterized channel properties of these variants by expressing them in oocytes of Xenopus laevis and conducting cut-open oocyte voltage clamp electrophysiology. Our datasets indicate no significant change in absolute conductance and conductance-voltage relationships of most disease variants as compared to wild type (WT), when expressed either alone or co-expressed with WT-KCNB2. However, variants c.1141A>G (p.Thr381Ala) and c.641C>T (p.Thr214Met) show complete abrogation of currents when expressed alone with the former exhibiting a left shift in activation midpoint when expressed alone or with WT-KCNB2. The variants we studied, nevertheless, show collective features of increased inactivation shifted to hyperpolarized potentials. We suggest that the effects of the variants on channel inactivation result in hyper-excitability of neurons, which contributes to disease manifestations.


Assuntos
Epilepsia , Mutação de Sentido Incorreto , Transtornos do Neurodesenvolvimento , Canais de Potássio Shab , Animais , Humanos , Potenciais de Ação , Epilepsia/genética , Neurônios , Oócitos , Xenopus laevis , Canais de Potássio Shab/genética , Canais de Potássio Shab/metabolismo , Transtornos do Neurodesenvolvimento/genética
2.
Genes (Basel) ; 14(8)2023 07 27.
Artigo em Inglês | MEDLINE | ID: mdl-37628590

RESUMO

The vacuolar H+-ATPase is a multisubunit enzyme which plays an essential role in the acidification and functions of lysosomes, endosomes, and synaptic vesicles. Many genes encoding subunits of V-ATPases, namely ATP6V0C, ATP6V1A, ATP6V0A1, and ATP6V1B2, have been associated with neurodevelopmental disorders and epilepsy. The autosomal dominant ATP6V1B2 p.Arg506* variant can cause both congenital deafness with onychodystrophy, autosomal dominant (DDOD) and deafness, onychodystrophy, osteodystrophy, mental retardation, and seizures syndromes (DOORS). Some but not all individuals with this truncating variant have intellectual disability and/or epilepsy, suggesting incomplete penetrance and/or variable expressivity. To further explore the impact of the p.Arg506* variant in neurodevelopment and epilepsy, we generated Atp6v1b2emR506* mutant mice and performed standardized phenotyping using the International Mouse Phenotyping Consortium (IMPC) pipeline. In addition, we assessed the EEG profile and seizure susceptibility of Atp6v1b2emR506* mice. Behavioral tests revealed that the mice present locomotor hyperactivity and show less anxiety-associated behaviors. Moreover, EEG analyses indicate that Atp6v1b2emR506* mutant mice have interictal epileptic activity and that both heterozygous (like patients) and homozygous mice have reduced seizure thresholds to pentylenetetrazol. Our results confirm that variants in ATP6V1B2 can cause seizures and that the Atp6v1b2emR506* heterozygous mouse model is a valuable tool to further explore the pathophysiology and potential treatments for vacuolar ATPases-associated epilepsy and disorders.


Assuntos
Artrogripose , Deficiência Intelectual , ATPases Vacuolares Próton-Translocadoras , Animais , Camundongos , Convulsões/genética , Causalidade , Adenosina Trifosfatases , Ansiedade , ATPases Vacuolares Próton-Translocadoras/genética
3.
Am J Hum Genet ; 110(7): 1068-1085, 2023 07 06.
Artigo em Inglês | MEDLINE | ID: mdl-37352860

RESUMO

ERI1 is a 3'-to-5' exoribonuclease involved in RNA metabolic pathways including 5.8S rRNA processing and turnover of histone mRNAs. Its biological and medical significance remain unclear. Here, we uncover a phenotypic dichotomy associated with bi-allelic ERI1 variants by reporting eight affected individuals from seven unrelated families. A severe spondyloepimetaphyseal dysplasia (SEMD) was identified in five affected individuals with missense variants but not in those with bi-allelic null variants, who showed mild intellectual disability and digital anomalies. The ERI1 missense variants cause a loss of the exoribonuclease activity, leading to defective trimming of the 5.8S rRNA 3' end and a decreased degradation of replication-dependent histone mRNAs. Affected-individual-derived induced pluripotent stem cells (iPSCs) showed impaired in vitro chondrogenesis with downregulation of genes regulating skeletal patterning. Our study establishes an entity previously unreported in OMIM and provides a model showing a more severe effect of missense alleles than null alleles within recessive genotypes, suggesting a key role of ERI1-mediated RNA metabolism in human skeletal patterning and chondrogenesis.


Assuntos
Exorribonucleases , Histonas , Humanos , Exorribonucleases/genética , Histonas/genética , Mutação de Sentido Incorreto/genética , RNA Ribossômico 5,8S , RNA , RNA Mensageiro/genética
4.
Hum Mutat ; 43(11): 1609-1628, 2022 11.
Artigo em Inglês | MEDLINE | ID: mdl-35904121

RESUMO

An expanding range of genetic syndromes are characterized by genome-wide disruptions in DNA methylation profiles referred to as episignatures. Episignatures are distinct, highly sensitive, and specific biomarkers that have recently been applied in clinical diagnosis of genetic syndromes. Episignatures are contained within the broader disorder-specific genome-wide DNA methylation changes, which can share significant overlap among different conditions. In this study, we performed functional genomic assessment and comparison of disorder-specific and overlapping genome-wide DNA methylation changes related to 65 genetic syndromes with previously described episignatures. We demonstrate evidence of disorder-specific and recurring genome-wide differentially methylated probes (DMPs) and regions (DMRs). The overall distribution of DMPs and DMRs across the majority of the neurodevelopmental genetic syndromes analyzed showed substantial enrichment in gene promoters and CpG islands, and under-representation of the more variable intergenic regions. Analysis showed significant enrichment of the DMPs and DMRs in gene pathways and processes related to neurodevelopment, including neurogenesis, synaptic signaling and synaptic transmission. This study expands beyond the diagnostic utility of DNA methylation episignatures by demonstrating correlation between the function of the mutated genes and the consequent genomic DNA methylation profiles as a key functional element in the molecular etiology of genetic neurodevelopmental disorders.


Assuntos
Metilação de DNA , Transtornos do Neurodesenvolvimento , Ilhas de CpG/genética , Metilação de DNA/genética , DNA Intergênico , Epigênese Genética , Humanos , Transtornos do Neurodesenvolvimento/diagnóstico , Transtornos do Neurodesenvolvimento/genética , Síndrome
5.
Genes Dev ; 36(11-12): 664-683, 2022 06 01.
Artigo em Inglês | MEDLINE | ID: mdl-35710139

RESUMO

Chromosomal translocations frequently promote carcinogenesis by producing gain-of-function fusion proteins. Recent studies have identified highly recurrent chromosomal translocations in patients with endometrial stromal sarcomas (ESSs) and ossifying fibromyxoid tumors (OFMTs), leading to an in-frame fusion of PHF1 (PCL1) to six different subunits of the NuA4/TIP60 complex. While NuA4/TIP60 is a coactivator that acetylates chromatin and loads the H2A.Z histone variant, PHF1 is part of the Polycomb repressive complex 2 (PRC2) linked to transcriptional repression of key developmental genes through methylation of histone H3 on lysine 27. In this study, we characterize the fusion protein produced by the EPC1-PHF1 translocation. The chimeric protein assembles a megacomplex harboring both NuA4/TIP60 and PRC2 activities and leads to mislocalization of chromatin marks in the genome, in particular over an entire topologically associating domain including part of the HOXD cluster. This is linked to aberrant gene expression-most notably increased expression of PRC2 target genes. Furthermore, we show that JAZF1-implicated with a PRC2 component in the most frequent translocation in ESSs, JAZF1-SUZ12-is a potent transcription activator that physically associates with NuA4/TIP60, its fusion creating outcomes similar to those of EPC1-PHF1 Importantly, the specific increased expression of PRC2 targets/HOX genes was also confirmed with ESS patient samples. Altogether, these results indicate that most chromosomal translocations linked to these sarcomas use the same molecular oncogenic mechanism through a physical merge of NuA4/TIP60 and PRC2 complexes, leading to mislocalization of histone marks and aberrant Polycomb target gene expression.


Assuntos
Neoplasias do Endométrio , Sarcoma do Estroma Endometrial , Sarcoma , Cromatina , Proteínas de Ligação a DNA/metabolismo , Neoplasias do Endométrio/genética , Neoplasias do Endométrio/metabolismo , Neoplasias do Endométrio/patologia , Feminino , Histonas/metabolismo , Humanos , Complexo Repressor Polycomb 2/genética , Complexo Repressor Polycomb 2/metabolismo , Proteínas do Grupo Polycomb/genética , Proteínas do Grupo Polycomb/metabolismo , Sarcoma/genética , Sarcoma do Estroma Endometrial/genética , Sarcoma do Estroma Endometrial/metabolismo , Sarcoma do Estroma Endometrial/patologia , Translocação Genética/genética
6.
JCI Insight ; 7(10)2022 05 23.
Artigo em Inglês | MEDLINE | ID: mdl-35603789

RESUMO

The eukaryotic CDC45/MCM2-7/GINS (CMG) helicase unwinds the DNA double helix during DNA replication. The GINS subcomplex is required for helicase activity and is, therefore, essential for DNA replication and cell viability. Here, we report the identification of 7 individuals from 5 unrelated families presenting with a Meier-Gorlin syndrome-like (MGS-like) phenotype associated with hypomorphic variants of GINS3, a gene not previously associated with this syndrome. We found that MGS-associated GINS3 variants affecting aspartic acid 24 (D24) compromised cell proliferation and caused accumulation of cells in S phase. These variants shortened the protein half-life, altered key protein interactions at the replisome, and negatively influenced DNA replication fork progression. Yeast expressing MGS-associated variants of PSF3 (the yeast GINS3 ortholog) also displayed impaired growth, S phase progression defects, and decreased Psf3 protein stability. We further showed that mouse embryos homozygous for a D24 variant presented intrauterine growth retardation and did not survive to birth, and that fibroblasts derived from these embryos displayed accelerated cellular senescence. Taken together, our findings implicate GINS3 in the pathogenesis of MGS and support the notion that hypomorphic variants identified in this gene impaired cell and organismal growth by compromising DNA replication.


Assuntos
Micrognatismo , Saccharomyces cerevisiae , Animais , Proteínas Cromossômicas não Histona , Microtia Congênita , Replicação do DNA/genética , Transtornos do Crescimento , Humanos , Camundongos , Micrognatismo/genética , Proteínas de Manutenção de Minicromossomo/genética , Patela/anormalidades
7.
HGG Adv ; 3(1): 100075, 2022 Jan 13.
Artigo em Inglês | MEDLINE | ID: mdl-35047860

RESUMO

Overlapping clinical phenotypes and an expanding breadth and complexity of genomic associations are a growing challenge in the diagnosis and clinical management of Mendelian disorders. The functional consequences and clinical impacts of genomic variation may involve unique, disorder-specific, genomic DNA methylation episignatures. In this study, we describe 19 novel episignature disorders and compare the findings alongside 38 previously established episignatures for a total of 57 episignatures associated with 65 genetic syndromes. We demonstrate increasing resolution and specificity ranging from protein complex, gene, sub-gene, protein domain, and even single nucleotide-level Mendelian episignatures. We show the power of multiclass modeling to develop highly accurate and disease-specific diagnostic classifiers. This study significantly expands the number and spectrum of disorders with detectable DNA methylation episignatures, improves the clinical diagnostic capabilities through the resolution of unsolved cases and the reclassification of variants of unknown clinical significance, and provides further insight into the molecular etiology of Mendelian conditions.

9.
Am J Hum Genet ; 108(5): 929-941, 2021 05 06.
Artigo em Inglês | MEDLINE | ID: mdl-33811806

RESUMO

Proteins involved in transcriptional regulation harbor a demonstrated enrichment of mutations in neurodevelopmental disorders. The Sin3 (Swi-independent 3)/histone deacetylase (HDAC) complex plays a central role in histone deacetylation and transcriptional repression. Among the two vertebrate paralogs encoding the Sin3 complex, SIN3A variants cause syndromic intellectual disability, but the clinical consequences of SIN3B haploinsufficiency in humans are uncharacterized. Here, we describe a syndrome hallmarked by intellectual disability, developmental delay, and dysmorphic facial features with variably penetrant autism spectrum disorder, congenital malformations, corpus callosum defects, and impaired growth caused by disruptive SIN3B variants. Using chromosomal microarray or exome sequencing, and through international data sharing efforts, we identified nine individuals with heterozygous SIN3B deletion or single-nucleotide variants. Five individuals harbor heterozygous deletions encompassing SIN3B that reside within a ∼230 kb minimal region of overlap on 19p13.11, two individuals have a rare nonsynonymous substitution, and two individuals have a single-nucleotide deletion that results in a frameshift and predicted premature termination codon. To test the relevance of SIN3B impairment to measurable aspects of the human phenotype, we disrupted the orthologous zebrafish locus by genome editing and transient suppression. The mutant and morphant larvae display altered craniofacial patterning, commissural axon defects, and reduced body length supportive of an essential role for Sin3 function in growth and patterning of anterior structures. To investigate further the molecular consequences of SIN3B variants, we quantified genome-wide enhancer and promoter activity states by using H3K27ac ChIP-seq. We show that, similar to SIN3A mutations, SIN3B disruption causes hyperacetylation of a subset of enhancers and promoters in peripheral blood mononuclear cells. Together, these data demonstrate that SIN3B haploinsufficiency leads to a hitherto unknown intellectual disability/autism syndrome, uncover a crucial role of SIN3B in the central nervous system, and define the epigenetic landscape associated with Sin3 complex impairment.


Assuntos
Transtorno do Espectro Autista/genética , Haploinsuficiência/genética , Histona Desacetilases/metabolismo , Deficiência Intelectual/genética , Proteínas Repressoras/genética , Acetilação , Adolescente , Animais , Criança , Pré-Escolar , Variações do Número de Cópias de DNA/genética , Feminino , Histonas/química , Histonas/metabolismo , Humanos , Lactente , Larva/genética , Imageamento por Ressonância Magnética , Masculino , Pessoa de Meia-Idade , Modelos Moleculares , Mutação , Proteínas Repressoras/deficiência , Proteínas Repressoras/metabolismo , Síndrome , Adulto Jovem , Peixe-Zebra/genética , Proteínas de Peixe-Zebra/deficiência , Proteínas de Peixe-Zebra/genética
10.
Nucleic Acids Res ; 49(6): 3524-3545, 2021 04 06.
Artigo em Inglês | MEDLINE | ID: mdl-33660780

RESUMO

Vertebrate genomes contain major (>99.5%) and minor (<0.5%) introns that are spliced by the major and minor spliceosomes, respectively. Major intron splicing follows the exon-definition model, whereby major spliceosome components first assemble across exons. However, since most genes with minor introns predominately consist of major introns, formation of exon-definition complexes in these genes would require interaction between the major and minor spliceosomes. Here, we report that minor spliceosome protein U11-59K binds to the major spliceosome U2AF complex, thereby supporting a model in which the minor spliceosome interacts with the major spliceosome across an exon to regulate the splicing of minor introns. Inhibition of minor spliceosome snRNAs and U11-59K disrupted exon-bridging interactions, leading to exon skipping by the major spliceosome. The resulting aberrant isoforms contained a premature stop codon, yet were not subjected to nonsense-mediated decay, but rather bound to polysomes. Importantly, we detected elevated levels of these alternatively spliced transcripts in individuals with minor spliceosome-related diseases such as Roifman syndrome, Lowry-Wood syndrome and early-onset cerebellar ataxia. In all, we report that the minor spliceosome informs splicing by the major spliceosome through exon-definition interactions and show that minor spliceosome inhibition results in aberrant alternative splicing in disease.


Assuntos
Processamento Alternativo , Éxons , Íntrons , Spliceossomos/metabolismo , Animais , Proteínas Reguladoras de Apoptose/metabolismo , Cardiomiopatias/genética , Células Cultivadas , Ataxia Cerebelar/genética , Transtornos do Crescimento/genética , Humanos , Deficiência Intelectual/genética , Deficiência Intelectual Ligada ao Cromossomo X/genética , Camundongos , Microcefalia/genética , Degradação do RNAm Mediada por Códon sem Sentido , Osteocondrodisplasias/genética , Polirribossomos/metabolismo , Doenças da Imunodeficiência Primária/genética , RNA Nuclear Pequeno/antagonistas & inibidores , Doenças Retinianas/genética , Fatores de Transcrição/metabolismo
11.
Am J Hum Genet ; 108(1): 134-147, 2021 01 07.
Artigo em Inglês | MEDLINE | ID: mdl-33340455

RESUMO

The ubiquitin-proteasome system facilitates the degradation of unstable or damaged proteins. UBR1-7, which are members of hundreds of E3 ubiquitin ligases, recognize and regulate the half-life of specific proteins on the basis of their N-terminal sequences ("N-end rule"). In seven individuals with intellectual disability, epilepsy, ptosis, hypothyroidism, and genital anomalies, we uncovered bi-allelic variants in UBR7. Their phenotype differs significantly from that of Johanson-Blizzard syndrome (JBS), which is caused by bi-allelic variants in UBR1, notably by the presence of epilepsy and the absence of exocrine pancreatic insufficiency and hypoplasia of nasal alae. While the mechanistic etiology of JBS remains uncertain, mutation of both Ubr1 and Ubr2 in the mouse or of the C. elegans UBR5 ortholog results in Notch signaling defects. Consistent with a potential role in Notch signaling, C. elegans ubr-7 expression partially overlaps with that of ubr-5, including in neurons, as well as the distal tip cell that plays a crucial role in signaling to germline stem cells via the Notch signaling pathway. Analysis of ubr-5 and ubr-7 single mutants and double mutants revealed genetic interactions with the Notch receptor gene glp-1 that influenced development and embryo formation. Collectively, our findings further implicate the UBR protein family and the Notch signaling pathway in a neurodevelopmental syndrome with epilepsy, ptosis, and hypothyroidism that differs from JBS. Further studies exploring a potential role in histone regulation are warranted given clinical overlap with KAT6B disorders and the interaction of UBR7 and UBR5 with histones.


Assuntos
Epilepsia/genética , Hipotireoidismo/genética , Transtornos do Neurodesenvolvimento/genética , Receptores Notch/genética , Transdução de Sinais/genética , Ubiquitina-Proteína Ligases/genética , Animais , Anus Imperfurado/genética , Caenorhabditis elegans/genética , Linhagem Celular , Displasia Ectodérmica/genética , Transtornos do Crescimento/genética , Células HEK293 , Perda Auditiva Neurossensorial/genética , Histonas/genética , Humanos , Deficiência Intelectual/genética , Camundongos , Mutação/genética , Nariz/anormalidades , Pancreatopatias/genética , Complexo de Endopeptidases do Proteassoma/genética
12.
Bone ; 141: 115601, 2020 12.
Artigo em Inglês | MEDLINE | ID: mdl-32827848

RESUMO

Lamin B receptor, a member of the sterol reductase family, is an inner nuclear membrane protein which binds lamin B proteins and is involved in the organization of heterochromatin. Mutations in LBR have been associated with a variety of disorders, such as Pelger-Huët anomaly, a benign abnormality affecting neutrophils, and Greenberg Dysplasia, a lethal condition in the perinatal period. We identified a homozygous LBR missense mutation (NM_002296.4: c.1366C > G, p.(Leu456Val)) in two adult sisters with a Lamin B receptor-related disorder associated with a skeletal dysplasia milder than Greenberg Dysplasia. Individual 1 has short stature with short limbs (mostly rhizomelic for the upper extremities, and mesomelic for the lower extremities), limited elbow extension. She required Achilles tenotomy, and does not have facial dysmorphisms. Individual 2 has similar skeletal features, but also has bowed femurs, osteopenia, spastic paraplegia of the lower limbs, equinovarus feet, a single kidney, neurogenic bladder, obstructive hydronephrosis, scoliosis and syndactyly of the toes. This report provides additional evidence of variability for Lamin B receptor-related disorders associated with a non-lethal skeletal dysplasia without Pelger-Huët anomaly. We describe a novel pathogenic variant that has not been previously associated with disease and demonstrate the effect of this variant on sterol C14-reductase activity.


Assuntos
Osteocondrodisplasias , Anomalia de Pelger-Huët , Adulto , Feminino , Homozigoto , Humanos , Osteocondrodisplasias/genética , Anomalia de Pelger-Huët/genética , Gravidez , Receptores Citoplasmáticos e Nucleares , Receptor de Lamina B
13.
Am J Hum Genet ; 107(3): 564-574, 2020 09 03.
Artigo em Inglês | MEDLINE | ID: mdl-32822602

RESUMO

KAT5 encodes an essential lysine acetyltransferase, previously called TIP60, which is involved in regulating gene expression, DNA repair, chromatin remodeling, apoptosis, and cell proliferation; but it remains unclear whether variants in this gene cause a genetic disease. Here, we study three individuals with heterozygous de novo missense variants in KAT5 that affect normally invariant residues, with one at the chromodomain (p.Arg53His) and two at or near the acetyl-CoA binding site (p.Cys369Ser and p.Ser413Ala). All three individuals have cerebral malformations, seizures, global developmental delay or intellectual disability, and severe sleep disturbance. Progressive cerebellar atrophy was also noted. Histone acetylation assays with purified variant KAT5 demonstrated that the variants decrease or abolish the ability of the resulting NuA4/TIP60 multi-subunit complexes to acetylate the histone H4 tail in chromatin. Transcriptomic analysis in affected individual fibroblasts showed deregulation of multiple genes that control development. Moreover, there was also upregulated expression of PER1 (a key gene involved in circadian control) in agreement with sleep anomalies in all of the individuals. In conclusion, dominant missense KAT5 variants cause histone acetylation deficiency with transcriptional dysregulation of multiples genes, thereby leading to a neurodevelopmental syndrome with sleep disturbance, cerebellar atrophy, and facial dysmorphisms, and suggesting a recognizable syndrome.


Assuntos
Atrofia/genética , Doenças Cerebelares/genética , Deficiência Intelectual/genética , Lisina Acetiltransferase 5/genética , Anormalidades Múltiplas/diagnóstico por imagem , Anormalidades Múltiplas/genética , Anormalidades Múltiplas/fisiopatologia , Adolescente , Adulto , Atrofia/diagnóstico por imagem , Atrofia/fisiopatologia , Doenças Cerebelares/diagnóstico por imagem , Doenças Cerebelares/fisiopatologia , Pré-Escolar , Cromatina/genética , Montagem e Desmontagem da Cromatina/genética , Reparo do DNA/genética , Epilepsia/diagnóstico por imagem , Epilepsia/genética , Epilepsia/fisiopatologia , Feminino , Heterozigoto , Histonas/genética , Humanos , Deficiência Intelectual/diagnóstico por imagem , Deficiência Intelectual/fisiopatologia , Masculino , Mutação de Sentido Incorreto/genética , Processamento de Proteína Pós-Traducional/genética
14.
Am J Hum Genet ; 106(4): 484-495, 2020 04 02.
Artigo em Inglês | MEDLINE | ID: mdl-32220290

RESUMO

Glycosylphosphatidylinositol (GPI)-anchored proteins are critical for embryogenesis, neurogenesis, and cell signaling. Variants in several genes participating in GPI biosynthesis and processing lead to decreased cell surface presence of GPI-anchored proteins (GPI-APs) and cause inherited GPI deficiency disorders (IGDs). In this report, we describe 12 individuals from nine unrelated families with 10 different bi-allelic PIGK variants. PIGK encodes a component of the GPI transamidase complex, which attaches the GPI anchor to proteins. Clinical features found in most individuals include global developmental delay and/or intellectual disability, hypotonia, cerebellar ataxia, cerebellar atrophy, and facial dysmorphisms. The majority of the individuals have epilepsy. Two individuals have slightly decreased levels of serum alkaline phosphatase, while eight do not. Flow cytometric analysis of blood and fibroblasts from affected individuals showed decreased cell surface presence of GPI-APs. The overexpression of wild-type (WT) PIGK in fibroblasts rescued the levels of cell surface GPI-APs. In a knockout cell line, transfection with WT PIGK also rescued the GPI-AP levels, but transfection with the two tested mutant variants did not. Our study not only expands the clinical and known genetic spectrum of IGDs, but it also expands the genetic differential diagnosis for cerebellar atrophy. Given the fact that cerebellar atrophy is seen in other IGDs, flow cytometry for GPI-APs should be considered in the work-ups of individuals presenting this feature.


Assuntos
Aciltransferases/genética , Moléculas de Adesão Celular/genética , Doenças Cerebelares/genética , Epilepsia/genética , Variação Genética/genética , Hipotonia Muscular/genética , Transtornos do Neurodesenvolvimento/genética , Anormalidades Múltiplas/genética , Alelos , Feminino , Humanos , Deficiência Intelectual/genética , Masculino , Malformações do Sistema Nervoso/genética , Linhagem , Síndrome
15.
Am J Hum Genet ; 106(3): 356-370, 2020 03 05.
Artigo em Inglês | MEDLINE | ID: mdl-32109418

RESUMO

Genetic syndromes frequently present with overlapping clinical features and inconclusive or ambiguous genetic findings which can confound accurate diagnosis and clinical management. An expanding number of genetic syndromes have been shown to have unique genomic DNA methylation patterns (called "episignatures"). Peripheral blood episignatures can be used for diagnostic testing as well as for the interpretation of ambiguous genetic test results. We present here an approach to episignature mapping in 42 genetic syndromes, which has allowed the identification of 34 robust disease-specific episignatures. We examine emerging patterns of overlap, as well as similarities and hierarchical relationships across these episignatures, to highlight their key features as they are related to genetic heterogeneity, dosage effect, unaffected carrier status, and incomplete penetrance. We demonstrate the necessity of multiclass modeling for accurate genetic variant classification and show how disease classification using a single episignature at a time can sometimes lead to classification errors in closely related episignatures. We demonstrate the utility of this tool in resolving ambiguous clinical cases and identification of previously undiagnosed cases through mass screening of a large cohort of subjects with developmental delays and congenital anomalies. This study more than doubles the number of published syndromes with DNA methylation episignatures and, most significantly, opens new avenues for accurate diagnosis and clinical assessment in individuals affected by these disorders.


Assuntos
Metilação de DNA , Transtornos do Neurodesenvolvimento/genética , Fenótipo , Estudos de Coortes , Heterogeneidade Genética , Humanos , Síndrome
16.
Sci Adv ; 6(4): eaax0021, 2020 01.
Artigo em Inglês | MEDLINE | ID: mdl-32010779

RESUMO

Lysine acetyltransferase 6A (KAT6A) and its paralog KAT6B form stoichiometric complexes with bromodomain- and PHD finger-containing protein 1 (BRPF1) for acetylation of histone H3 at lysine 23 (H3K23). We report that these complexes also catalyze H3K23 propionylation in vitro and in vivo. Immunofluorescence microscopy and ATAC-See revealed the association of this modification with active chromatin. Brpf1 deletion obliterates the acylation in mouse embryos and fibroblasts. Moreover, we identify BRPF1 variants in 12 previously unidentified cases of syndromic intellectual disability and demonstrate that these cases and known BRPF1 variants impair H3K23 propionylation. Cardiac anomalies are present in a subset of the cases. H3K23 acylation is also impaired by cancer-derived somatic BRPF1 mutations. Valproate, vorinostat, propionate and butyrate promote H3K23 acylation. These results reveal the dual functionality of BRPF1-KAT6 complexes, shed light on mechanisms underlying related developmental disorders and various cancers, and suggest mutation-based therapy for medical conditions with deficient histone acylation.


Assuntos
Proteínas Adaptadoras de Transdução de Sinal/metabolismo , Proteínas de Ligação a DNA/metabolismo , Histona Acetiltransferases/metabolismo , Histonas/metabolismo , Neoplasias/etiologia , Neoplasias/metabolismo , Transtornos do Neurodesenvolvimento/etiologia , Transtornos do Neurodesenvolvimento/metabolismo , Acetilação , Proteínas Adaptadoras de Transdução de Sinal/genética , Sequência de Aminoácidos , Animais , Encéfalo/anormalidades , Encéfalo/diagnóstico por imagem , Linhagem Celular , Análise Mutacional de DNA , Proteínas de Ligação a DNA/genética , Suscetibilidade a Doenças , Predisposição Genética para Doença , Histona Acetiltransferases/genética , Humanos , Imageamento por Ressonância Magnética , Camundongos , Camundongos Knockout , Modelos Biológicos , Complexos Multiproteicos/metabolismo , Mutação , Neoplasias/diagnóstico , Transtornos do Neurodesenvolvimento/diagnóstico , Fenótipo , Ligação Proteica , Domínios e Motivos de Interação entre Proteínas , Processamento de Proteína Pós-Traducional , Síndrome
17.
J Clin Invest ; 130(3): 1431-1445, 2020 03 02.
Artigo em Inglês | MEDLINE | ID: mdl-31794431

RESUMO

Epigenetic integrity is critical for many eukaryotic cellular processes. An important question is how different epigenetic regulators control development and influence disease. Lysine acetyltransferase 8 (KAT8) is critical for acetylation of histone H4 at lysine 16 (H4K16), an evolutionarily conserved epigenetic mark. It is unclear what roles KAT8 plays in cerebral development and human disease. Here, we report that cerebrum-specific knockout mice displayed cerebral hypoplasia in the neocortex and hippocampus, along with improper neural stem and progenitor cell (NSPC) development. Mutant cerebrocortical neuroepithelia exhibited faulty proliferation, aberrant neurogenesis, massive apoptosis, and scant H4K16 propionylation. Mutant NSPCs formed poor neurospheres, and pharmacological KAT8 inhibition abolished neurosphere formation. Moreover, we describe KAT8 variants in 9 patients with intellectual disability, seizures, autism, dysmorphisms, and other anomalies. The variants altered chromobarrel and catalytic domains of KAT8, thereby impairing nucleosomal H4K16 acetylation. Valproate was effective for treating epilepsy in at least 2 of the individuals. This study uncovers a critical role of KAT8 in cerebral and NSPC development, identifies 9 individuals with KAT8 variants, and links deficient H4K16 acylation directly to intellectual disability, epilepsy, and other developmental anomalies.


Assuntos
Hipocampo/enzimologia , Histona Acetiltransferases/metabolismo , Deficiência Intelectual/enzimologia , Neocórtex/enzimologia , Células-Tronco Neurais/enzimologia , Acetilação , Animais , Células HEK293 , Hipocampo/patologia , Histona Acetiltransferases/genética , Humanos , Deficiência Intelectual/patologia , Camundongos , Camundongos Knockout , Neocórtex/patologia , Células-Tronco Neurais/patologia , Nucleossomos/genética , Nucleossomos/metabolismo
18.
Am J Hum Genet ; 105(6): 1237-1253, 2019 12 05.
Artigo em Inglês | MEDLINE | ID: mdl-31785787

RESUMO

We report an early-onset autosomal-recessive neurological disease with cerebellar atrophy and lysosomal dysfunction. We identified bi-allelic loss-of-function (LoF) variants in Oxidative Resistance 1 (OXR1) in five individuals from three families; these individuals presented with a history of severe global developmental delay, current intellectual disability, language delay, cerebellar atrophy, and seizures. While OXR1 is known to play a role in oxidative stress resistance, its molecular functions are not well established. OXR1 contains three conserved domains: LysM, GRAM, and TLDc. The gene encodes at least six transcripts, including some that only consist of the C-terminal TLDc domain. We utilized Drosophila to assess the phenotypes associated with loss of mustard (mtd), the fly homolog of OXR1. Strong LoF mutants exhibit late pupal lethality or pupal eclosion defects. Interestingly, although mtd encodes 26 transcripts, severe LoF and null mutations can be rescued by a single short human OXR1 cDNA that only contains the TLDc domain. Similar rescue is observed with the TLDc domain of NCOA7, another human homolog of mtd. Loss of mtd in neurons leads to massive cell loss, early death, and an accumulation of aberrant lysosomal structures, similar to what we observe in fibroblasts of affected individuals. Our data indicate that mtd and OXR1 are required for proper lysosomal function; this is consistent with observations that NCOA7 is required for lysosomal acidification.


Assuntos
Atrofia/patologia , Doenças Cerebelares/patologia , Lisossomos/patologia , Proteínas Mitocondriais/metabolismo , Doenças do Sistema Nervoso/patologia , Estresse Oxidativo , Adolescente , Adulto , Animais , Atrofia/genética , Atrofia/metabolismo , Doenças Cerebelares/genética , Doenças Cerebelares/metabolismo , Criança , Drosophila melanogaster/crescimento & desenvolvimento , Drosophila melanogaster/metabolismo , Feminino , Fibroblastos/metabolismo , Fibroblastos/patologia , Humanos , Lisossomos/metabolismo , Masculino , Proteínas Mitocondriais/genética , Doenças do Sistema Nervoso/genética , Doenças do Sistema Nervoso/metabolismo , Linhagem , Fenótipo , Adulto Jovem
19.
Am J Hum Genet ; 105(3): 534-548, 2019 09 05.
Artigo em Inglês | MEDLINE | ID: mdl-31422819

RESUMO

Early-infantile encephalopathies with epilepsy are devastating conditions mandating an accurate diagnosis to guide proper management. Whole-exome sequencing was used to investigate the disease etiology in four children from independent families with intellectual disability and epilepsy, revealing bi-allelic GOT2 mutations. In-depth metabolic studies in individual 1 showed low plasma serine, hypercitrullinemia, hyperlactatemia, and hyperammonemia. The epilepsy was serine and pyridoxine responsive. Functional consequences of observed mutations were tested by measuring enzyme activity and by cell and animal models. Zebrafish and mouse models were used to validate brain developmental and functional defects and to test therapeutic strategies. GOT2 encodes the mitochondrial glutamate oxaloacetate transaminase. GOT2 enzyme activity was deficient in fibroblasts with bi-allelic mutations. GOT2, a member of the malate-aspartate shuttle, plays an essential role in the intracellular NAD(H) redox balance. De novo serine biosynthesis was impaired in fibroblasts with GOT2 mutations and GOT2-knockout HEK293 cells. Correcting the highly oxidized cytosolic NAD-redox state by pyruvate supplementation restored serine biosynthesis in GOT2-deficient cells. Knockdown of got2a in zebrafish resulted in a brain developmental defect associated with seizure-like electroencephalography spikes, which could be rescued by supplying pyridoxine in embryo water. Both pyridoxine and serine synergistically rescued embryonic developmental defects in zebrafish got2a morphants. The two treated individuals reacted favorably to their treatment. Our data provide a mechanistic basis for the biochemical abnormalities in GOT2 deficiency that may also hold for other MAS defects.


Assuntos
Alelos , Ácido Aspártico/metabolismo , Encefalopatias/genética , Proteínas de Ligação a Ácido Graxo/genética , Malatos/metabolismo , Mutação , Animais , Criança , Pré-Escolar , Feminino , Técnicas de Silenciamento de Genes , Células HEK293 , Humanos , Masculino , Camundongos , Sequenciamento do Exoma
20.
Am J Hum Genet ; 105(3): 625-630, 2019 09 05.
Artigo em Inglês | MEDLINE | ID: mdl-31303264

RESUMO

Rothmund-Thomson syndrome (RTS) is an autosomal-recessive disorder characterized by poikiloderma, sparse hair, short stature, and skeletal anomalies. Type 2 RTS, which is defined by the presence of bi-allelic mutations in RECQL4, is characterized by increased cancer susceptibility and skeletal anomalies, whereas the genetic basis of RTS type 1, which is associated with juvenile cataracts, is unknown. We studied ten individuals, from seven families, who had RTS type 1 and identified a deep intronic splicing mutation of the ANAPC1 gene, a component of the anaphase-promoting complex/cyclosome (APC/C), in all affected individuals, either in the homozygous state or in trans with another mutation. Fibroblast studies showed that the intronic mutation causes the activation of a 95 bp pseudoexon, leading to mRNAs with premature termination codons and nonsense-mediated decay, decreased ANAPC1 protein levels, and prolongation of interphase. Interestingly, mice that were heterozygous for a knockout mutation have an increased incidence of cataracts. Our results demonstrate that deficiency in the APC/C is a cause of RTS type 1 and suggest a possible link between the APC/C and RECQL4 helicase because both proteins are involved in DNA repair and replication.


Assuntos
Ciclossomo-Complexo Promotor de Anáfase/genética , Subunidade Apc1 do Ciclossomo-Complexo Promotor de Anáfase/genética , Mutação , Síndrome de Rothmund-Thomson/genética , Humanos
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