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1.
Am J Hum Genet ; 103(6): 1009-1021, 2018 12 06.
Artigo em Inglês | MEDLINE | ID: mdl-30471716

RESUMO

To date, mutations in 15 actin- or microtubule-associated genes have been associated with the cortical malformation lissencephaly and variable brainstem hypoplasia. During a multicenter review, we recognized a rare lissencephaly variant with a complex brainstem malformation in three unrelated children. We searched our large brain-malformation databases and found another five children with this malformation (as well as one with a less severe variant), analyzed available whole-exome or -genome sequencing data, and tested ciliogenesis in two affected individuals. The brain malformation comprised posterior predominant lissencephaly and midline crossing defects consisting of absent anterior commissure and a striking W-shaped brainstem malformation caused by small or absent pontine crossing fibers. We discovered heterozygous de novo missense variants or an in-frame deletion involving highly conserved zinc-binding residues within the GAR domain of MACF1 in the first eight subjects. We studied cilium formation and found a higher proportion of mutant cells with short cilia than of control cells with short cilia. A ninth child had similar lissencephaly but only subtle brainstem dysplasia associated with a heterozygous de novo missense variant in the spectrin repeat domain of MACF1. Thus, we report variants of the microtubule-binding GAR domain of MACF1 as the cause of a distinctive and most likely pathognomonic brain malformation. A gain-of-function or dominant-negative mechanism appears likely given that many heterozygous mutations leading to protein truncation are included in the ExAC Browser. However, three de novo variants in MACF1 have been observed in large schizophrenia cohorts.


Assuntos
Orientação de Axônios/genética , Movimento Celular/genética , Sequência Conservada/genética , Proteínas dos Microfilamentos/genética , Mutação/genética , Neurônios/patologia , Zinco/metabolismo , Adolescente , Tronco Encefálico/patologia , Criança , Pré-Escolar , Cílios/genética , Feminino , Humanos , Lisencefalia/genética , Masculino , Microtúbulos/genética , Malformações do Sistema Nervoso/genética
2.
Am J Hum Genet ; 101(2): 291-299, 2017 Aug 03.
Artigo em Inglês | MEDLINE | ID: mdl-28777934

RESUMO

Progressive childhood encephalopathy is an etiologically heterogeneous condition characterized by progressive central nervous system dysfunction in association with a broad range of morbidity and mortality. The causes of encephalopathy can be either non-genetic or genetic. Identifying the genetic causes and dissecting the underlying mechanisms are critical to understanding brain development and improving treatments. Here, we report that variants in TRAPPC12 result in progressive childhood encephalopathy. Three individuals from two unrelated families have either a homozygous deleterious variant (c.145delG [p.Glu49Argfs∗14]) or compound-heterozygous variants (c.360dupC [p.Glu121Argfs∗7] and c.1880C>T [p. Ala627Val]). The clinical phenotypes of the three individuals are strikingly similar: severe disability, microcephaly, hearing loss, spasticity, and characteristic brain imaging findings. Fibroblasts derived from all three individuals showed a fragmented Golgi that could be rescued by expression of wild-type TRAPPC12. Protein transport from the endoplasmic reticulum to and through the Golgi was delayed. TRAPPC12 is a member of the TRAPP protein complex, which functions in membrane trafficking. Variants in several other genes encoding members of the TRAPP complex have been associated with overlapping clinical presentations, indicating shared and distinct functions for each complex member. Detailed understanding of the TRAPP-opathies will illuminate the role of membrane protein transport in human disease.


Assuntos
Encefalopatias/genética , Retículo Endoplasmático/metabolismo , Complexo de Golgi/patologia , Proteínas de Membrana Transportadoras/genética , Transporte Proteico/genética , Fatores de Transcrição/genética , Atrofia/patologia , Sequência de Bases , Encéfalo/patologia , Encefalopatias/patologia , Células Cultivadas , Pré-Escolar , Exoma/genética , Feminino , Predisposição Genética para Doença , Humanos , Lactente , Imageamento por Ressonância Magnética , Masculino , Transporte Proteico/fisiologia , Análise de Sequência de DNA
3.
Am J Hum Genet ; 101(1): 23-36, 2017 Jul 06.
Artigo em Inglês | MEDLINE | ID: mdl-28625504

RESUMO

Joubert syndrome (JS) is a recessive neurodevelopmental disorder characterized by hypotonia, ataxia, abnormal eye movements, and variable cognitive impairment. It is defined by a distinctive brain malformation known as the "molar tooth sign" on axial MRI. Subsets of affected individuals have malformations such as coloboma, polydactyly, and encephalocele, as well as progressive retinal dystrophy, fibrocystic kidney disease, and liver fibrosis. More than 35 genes have been associated with JS, but in a subset of families the genetic cause remains unknown. All of the gene products localize in and around the primary cilium, making JS a canonical ciliopathy. Ciliopathies are unified by their overlapping clinical features and underlying mechanisms involving ciliary dysfunction. In this work, we identify biallelic rare, predicted-deleterious ARMC9 variants (stop-gain, missense, splice-site, and single-exon deletion) in 11 individuals with JS from 8 families, accounting for approximately 1% of the disorder. The associated phenotypes range from isolated neurological involvement to JS with retinal dystrophy, additional brain abnormalities (e.g., heterotopia, Dandy-Walker malformation), pituitary insufficiency, and/or synpolydactyly. We show that ARMC9 localizes to the basal body of the cilium and is upregulated during ciliogenesis. Typical ciliopathy phenotypes (curved body shape, retinal dystrophy, coloboma, and decreased cilia) in a CRISPR/Cas9-engineered zebrafish mutant model provide additional support for ARMC9 as a ciliopathy-associated gene. Identifying ARMC9 mutations as a cause of JS takes us one step closer to a full genetic understanding of this important disorder and enables future functional work to define the central biological mechanisms underlying JS and other ciliopathies.


Assuntos
Anormalidades Múltiplas/genética , Proteínas do Domínio Armadillo/genética , Corpos Basais/metabolismo , Cerebelo/anormalidades , Ciliopatias/genética , Anormalidades do Olho/genética , Doenças Renais Císticas/genética , Mutação/genética , Retina/anormalidades , Proteínas de Peixe-Zebra/genética , Peixe-Zebra/genética , Anormalidades Múltiplas/patologia , Animais , Proteínas do Domínio Armadillo/metabolismo , Sequência de Bases , Encéfalo/patologia , Cerebelo/patologia , Cílios/metabolismo , Ciliopatias/patologia , Diagnóstico por Imagem , Exoma/genética , Anormalidades do Olho/patologia , Predisposição Genética para Doença , Humanos , Doenças Renais Císticas/patologia , Fenótipo , Retina/patologia , Análise de Sequência de DNA , Regulação para Cima/genética , Proteínas de Peixe-Zebra/metabolismo
4.
Am J Med Genet C Semin Med Genet ; 178(4): 432-439, 2018 12.
Artigo em Inglês | MEDLINE | ID: mdl-30580482

RESUMO

Rhombencephalosynapsis (RES) is a unique cerebellar malformation characterized by fusion of the cerebellar hemispheres with partial or complete absence of a recognizable cerebellar vermis. Subsets of patients also have other brain malformations such as midbrain fusion with aqueductal stenosis, characteristic craniofacial features (prominent forehead, flat midface, hypertelorism, ear abnormalities), and somatic malformations (heart, kidney, spine, and limb defects). Similar to known genetic brain malformations, the RES cerebellar malformation is highly stereotyped, yet no genetic causes have been identified. Here, we outline our current understanding of the genetic basis for RES, discuss limitations, and outline future approaches to identifying the causes of this fascinating brain malformation.


Assuntos
Doenças Cerebelares/diagnóstico , Doenças Cerebelares/genética , Cerebelo/anormalidades , Transtornos do Crescimento/diagnóstico , Rombencéfalo/anormalidades , Transtornos do Crescimento/genética , Humanos , Rombencéfalo/patologia
5.
Genet Med ; 20(2): 223-233, 2018 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-28771248

RESUMO

PurposeNext-generation sequencing (NGS) often identifies multiple rare predicted-deleterious variants (RDVs) in different genes associated with a recessive disorder in a given patient. Such variants have been proposed to contribute to digenicity/oligogenicity or "triallelism" or to act as genetic modifiers.MethodsUsing the recessive ciliopathy Joubert syndrome (JBTS) as a model, we investigated these possibilities systematically, relying on NGS of known JBTS genes in a large JBTS and two control cohorts.Results65% of affected individuals had a recessive genetic cause, while 4.9% were candidates for di-/oligogenicity, harboring heterozygous RDVs in two or more genes, compared with 4.2-8% in controls (P = 0.66-0.21). Based on Exome Aggregation Consortium (ExAC) allele frequencies, the probability of cumulating RDVs in any two JBTS genes is 9.3%. We found no support for triallelism, as no unaffected siblings carried the same biallelic RDVs as their affected relative. Sixty percent of individuals sharing identical causal RDVs displayed phenotypic discordance. Although 38% of affected individuals harbored RDVs in addition to the causal mutations, their presence did not correlate with phenotypic severity.ConclusionOur data offer little support for triallelism or digenicity/oligogenicity as clinically relevant inheritance modes in JBTS. While phenotypic discordance supports the existence of genetic modifiers, identifying clinically relevant modifiers remains challenging.


Assuntos
Genes Recessivos , Estudos de Associação Genética , Doenças Genéticas Inatas/diagnóstico , Doenças Genéticas Inatas/genética , Predisposição Genética para Doença , Variação Genética , Anormalidades Múltiplas/diagnóstico , Anormalidades Múltiplas/genética , Alelos , Cerebelo/anormalidades , Anormalidades do Olho/diagnóstico , Anormalidades do Olho/genética , Genes Modificadores , Estudos de Associação Genética/métodos , Humanos , Doenças Renais Císticas/diagnóstico , Doenças Renais Císticas/genética , Modelos Genéticos , Herança Multifatorial , Mutação , Fenótipo , Retina/anormalidades
6.
J Clin Invest ; 130(8): 4423-4439, 2020 08 03.
Artigo em Inglês | MEDLINE | ID: mdl-32453716

RESUMO

Joubert syndrome (JBTS) is a recessive neurodevelopmental ciliopathy characterized by a pathognomonic hindbrain malformation. All known JBTS genes encode proteins involved in the structure or function of primary cilia, ubiquitous antenna-like organelles essential for cellular signal transduction. Here, we used the recently identified JBTS-associated protein armadillo repeat motif-containing 9 (ARMC9) in tandem-affinity purification and yeast 2-hybrid screens to identify a ciliary module whose dysfunction underlies JBTS. In addition to the known JBTS-associated proteins CEP104 and CSPP1, we identified coiled-coil domain containing 66 (CCDC66) and TOG array regulator of axonemal microtubules 1 (TOGARAM1) as ARMC9 interaction partners. We found that TOGARAM1 variants cause JBTS and disrupt TOGARAM1 interaction with ARMC9. Using a combination of protein interaction analyses, characterization of patient-derived fibroblasts, and analysis of CRISPR/Cas9-engineered zebrafish and hTERT-RPE1 cells, we demonstrated that dysfunction of ARMC9 or TOGARAM1 resulted in short cilia with decreased axonemal acetylation and polyglutamylation, but relatively intact transition zone function. Aberrant serum-induced ciliary resorption and cold-induced depolymerization in ARMC9 and TOGARAM1 patient cell lines suggest a role for this new JBTS-associated protein module in ciliary stability.


Assuntos
Anormalidades Múltiplas , Proteínas do Domínio Armadillo , Cerebelo/anormalidades , Cílios , Anormalidades do Olho , Doenças Renais Císticas , Retina/anormalidades , Proteínas de Peixe-Zebra , Peixe-Zebra , Anormalidades Múltiplas/genética , Anormalidades Múltiplas/metabolismo , Acetilação , Animais , Proteínas do Domínio Armadillo/genética , Proteínas do Domínio Armadillo/metabolismo , Sistemas CRISPR-Cas , Cerebelo/metabolismo , Cílios/genética , Cílios/metabolismo , Modelos Animais de Doenças , Anormalidades do Olho/genética , Anormalidades do Olho/metabolismo , Humanos , Doenças Renais Císticas/genética , Doenças Renais Císticas/metabolismo , Peptídeos/genética , Peptídeos/metabolismo , Retina/metabolismo , Peixe-Zebra/genética , Peixe-Zebra/metabolismo , Proteínas de Peixe-Zebra/genética , Proteínas de Peixe-Zebra/metabolismo
7.
Cilia ; 6: 2, 2017.
Artigo em Inglês | MEDLINE | ID: mdl-28344780

RESUMO

BACKGROUND: The discovery of disease pathogenesis requires systematic agnostic screening of multiple homeostatic processes that may become deregulated. We illustrate this principle in the evaluation and diagnosis of a 5-year-old boy with Joubert syndrome type 10 (JBTS10). He carried the OFD1 mutation p.Gln886Lysfs*2 (NM_003611.2: c.2656del) and manifested features of Joubert syndrome. METHODS: We integrated exome sequencing, MALDI-TOF mass spectrometry analyses of plasma and cultured dermal fibroblasts glycomes, and full clinical evaluation of the proband. Analyses of cilia formation and lectin staining were performed by immunofluorescence. Measurement of cellular nucleotide sugar levels was performed with high-performance anion-exchange chromatography with pulsed amperometric detection. Statistical analyses utilized the Student's and Fisher's exact t tests. RESULTS: Glycome analyses of plasma and cultured dermal fibroblasts identified abnormal N- and O-linked glycosylation profiles. These findings replicated in two unrelated males with OFD1 mutations. Cultured fibroblasts from affected individuals had a defect in ciliogenesis. The proband's fibroblasts also had an abnormally elevated nuclear sialylation signature and increased total cellular levels of CMP-sialic acid. Ciliogenesis and each glycosylation anomaly were rescued by expression of wild-type OFD1. CONCLUSIONS: The rescue of ciliogenesis and glycosylation upon reintroduction of WT OFD1 suggests that both contribute to the pathogenesis of JBTS10.

8.
Elife ; 42015 Dec 23.
Artigo em Inglês | MEDLINE | ID: mdl-26701906

RESUMO

Changes in gene activity are essential for evolutionary diversification. Yet, elucidating the cellular behaviors that underlie modifications to adult form remains a profound challenge. We use neural crest-derived adult pigmentation of zebrafish and pearl danio to uncover cellular bases for alternative pattern states. We show that stripes in zebrafish require a novel class of thin, fast cellular projection to promote Delta-Notch signaling over long distances from cells of the xanthophore lineage to melanophores. Projections depended on microfilaments and microtubules, exhibited meandering trajectories, and stabilized on target cells to which they delivered membraneous vesicles. By contrast, the uniformly patterned pearl danio lacked such projections, concomitant with Colony stimulating factor 1-dependent changes in xanthophore differentiation that likely curtail signaling available to melanophores. Our study reveals a novel mechanism of cellular communication, roles for differentiation state heterogeneity in pigment cell interactions, and an unanticipated morphogenetic behavior contributing to a striking difference in adult form.


Assuntos
Comunicação Celular , Cyprinidae/fisiologia , Regulação da Expressão Gênica , Melanóforos/fisiologia , Pigmentos Biológicos/metabolismo , Vesículas Secretórias/metabolismo , Transdução de Sinais , Animais , Cyprinidae/genética
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