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1.
Hum Mol Genet ; 30(23): 2215-2224, 2021 11 16.
Artigo em Inglês | MEDLINE | ID: mdl-34230955

RESUMO

CHARGE syndrome is an autosomal dominant malformation disorder caused by pathogenic variants in the chromatin remodeler CHD7. Affected are craniofacial structures, cranial nerves and multiple organ systems. Depending on the combination of malformations present, its distinction from other congenital disorders can be challenging. To gain a better insight into the regulatory disturbances in CHARGE syndrome, we performed RNA-Seq analysis on blood samples of 19 children with CHARGE syndrome and a confirmed disease-causing CHD7 variant in comparison with healthy control children. Our analysis revealed a distinct CHARGE syndrome pattern with downregulation of genes that are linked to disorders described to mimic the CHARGE phenotype, i.e. KMT2D and KDM6A (Kabuki syndrome), EP300 and CREBBP (Rubinstein-Taybi syndrome) and ARID1A and ARID1B (Coffin-Siris syndrome). Furthermore, by performing protein-protein interaction studies using co-immunoprecipitation, direct yeast-two hybrid and in situ proximity ligation assays, we could demonstrate an interplay between CHD7, KMT2D, KDM6A and EP300. In summary, our data demonstrate a mechanistic and regulatory link between the developmental disorders CHARGE-, Kabuki- and Rubinstein Taybi-syndrome providing an explanation for the overlapping phenotypes.


Assuntos
Síndrome CHARGE/diagnóstico , Síndrome CHARGE/genética , Estudos de Associação Genética , Doenças Genéticas Inatas/diagnóstico , Doenças Genéticas Inatas/genética , Predisposição Genética para Doença , Fatores Etários , Síndrome CHARGE/metabolismo , Proteínas de Transporte , DNA Helicases/genética , DNA Helicases/metabolismo , Proteínas de Ligação a DNA/genética , Proteínas de Ligação a DNA/metabolismo , Perfilação da Expressão Gênica , Estudos de Associação Genética/métodos , Doenças Genéticas Inatas/metabolismo , Marcadores Genéticos , Variação Genética , Humanos , Imunoprecipitação , Mutação , Proteínas de Neoplasias/genética , Proteínas de Neoplasias/metabolismo , Fenótipo , Ligação Proteica , RNA-Seq
2.
Genesis ; 59(1-2): e23404, 2021 02.
Artigo em Inglês | MEDLINE | ID: mdl-33351273

RESUMO

Neurocristopathies are human congenital syndromes that arise from defects in neural crest (NC) development and are typically associated with malformations of the craniofacial skeleton. Genetic analyses have been very successful in identifying pathogenic mutations, however, model organisms are required to characterize how these mutations affect embryonic development thereby leading to complex clinical conditions. The African clawed frog Xenopus laevis provides a broad range of in vivo and in vitro tools allowing for a detailed characterization of NC development. Due to the conserved nature of craniofacial morphogenesis in vertebrates, Xenopus is an efficient and versatile system to dissect the morphological and cellular phenotypes as well as the signaling events leading to NC defects. Here, we review a set of techniques and resources how Xenopus can be used as a disease model to investigate the pathogenesis of Kabuki syndrome and neurocristopathies in a wider sense.


Assuntos
Anormalidades Múltiplas/genética , Modelos Animais de Doenças , Face/anormalidades , Doenças Hematológicas/genética , Doenças Vestibulares/genética , Xenopus laevis/genética , Anormalidades Múltiplas/patologia , Animais , Face/patologia , Doenças Hematológicas/patologia , Histona Desmetilases/genética , Histona-Lisina N-Metiltransferase/genética , Crista Neural/metabolismo , Crista Neural/patologia , Doenças Vestibulares/patologia , Proteínas de Xenopus/genética , Xenopus laevis/fisiologia
3.
Hum Mol Genet ; 27(8): 1343-1352, 2018 04 15.
Artigo em Inglês | MEDLINE | ID: mdl-29432577

RESUMO

CHARGE syndrome is an autosomal dominant malformation disorder caused by heterozygous loss of function mutations in the chromatin remodeler CHD7. Chd7 regulates the expression of Sema3a, which also contributes to the pathogenesis of Kallmann syndrome, a heterogeneous condition with the typical features hypogonadotropic hypogonadism and an impaired sense of smell. Both features are common in CHARGE syndrome suggesting that SEMA3A may provide a genetic link between these syndromes. Indeed, we find evidence that SEMA3A plays a role in the pathogenesis of CHARGE syndrome. First, Chd7 is enriched at the Sema3a promotor in neural crest cells and loss of function of Chd7 inhibits Sema3a expression. Second, using a Xenopus CHARGE model, we show that human SEMA3A rescues Chd7 loss of function. Third, to elucidate if SEMA3A mutations in addition to CHD7 mutations also contribute to the severity of the CHARGE phenotype, we screened 31 CHD7-positive patients and identified one patient with a heterozygous non-synonymous SEMA3A variant, c.2002A>G (p.I668V). By analyzing protein expression and processing, we did not observe any differences of the p.I668V variant compared with wild-type SEMA3A, while a pathogenic SEMA3A variant p.R66W recently described in a patient with Kallmann syndrome did affect protein secretion. Furthermore, the p.I668V variant, but not the pathogenic p.R66W variant, rescues Chd7 loss of function in Xenopus, indicating that the p.I668V variant is likely benign. Thus, SEMA3A is part of an epigenetic loop that plays a role in the pathogenesis of CHARGE syndrome, however, it seems not to act as a common direct modifier.


Assuntos
Síndrome CHARGE/genética , DNA Helicases/genética , Proteínas de Ligação a DNA/genética , Epigênese Genética , Crista Neural/metabolismo , Semaforina-3A/genética , Animais , Síndrome CHARGE/metabolismo , Síndrome CHARGE/patologia , DNA Helicases/metabolismo , Proteínas de Ligação a DNA/metabolismo , Modelos Animais de Doenças , Embrião não Mamífero , Teste de Complementação Genética , Células HEK293 , Proteína Homeobox Nkx-2.5/genética , Proteína Homeobox Nkx-2.5/metabolismo , Humanos , Síndrome de Kallmann/genética , Síndrome de Kallmann/metabolismo , Síndrome de Kallmann/patologia , Mutação , Crista Neural/patologia , Regiões Promotoras Genéticas , Semaforina-3A/metabolismo , Índice de Gravidade de Doença , Xenopus laevis
4.
Hum Genet ; 139(11): 1363-1379, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-32424618

RESUMO

We report truncating de novo variants in specific exons of FBRSL1 in three unrelated children with an overlapping syndromic phenotype with respiratory insufficiency, postnatal growth restriction, microcephaly, global developmental delay and other malformations. The function of FBRSL1 is largely unknown. Interestingly, mutations in the FBRSL1 paralogue AUTS2 lead to an intellectual disability syndrome (AUTS2 syndrome). We determined human FBRSL1 transcripts and describe protein-coding forms by Western blot analysis as well as the cellular localization by immunocytochemistry stainings. All detected mutations affect the two short N-terminal isoforms, which show a ubiquitous expression in fetal tissues. Next, we performed a Fbrsl1 knockdown in Xenopus laevis embryos to explore the role of Fbrsl1 during development and detected craniofacial abnormalities and a disturbance in neurite outgrowth. The aberrant phenotype in Xenopus laevis embryos could be rescued with a human N-terminal isoform, while the long isoform and the N-terminal isoform containing the mutation p.Gln163* isolated from a patient could not rescue the craniofacial defects caused by Fbrsl1 depletion. Based on these data, we propose that the disruption of the validated N-terminal isoforms of FBRSL1 at critical timepoints during embryogenesis leads to a hitherto undescribed complex neurodevelopmental syndrome.


Assuntos
Deficiência Intelectual/genética , Linfocinas/genética , Mutação/genética , Anormalidades Múltiplas/genética , Adolescente , Animais , Criança , Éxons/genética , Humanos , Masculino , Fenótipo , Isoformas de Proteínas/genética , Síndrome , Fatores de Transcrição/genética
5.
J Med Genet ; 56(4): 261-264, 2019 04.
Artigo em Inglês | MEDLINE | ID: mdl-30120217

RESUMO

BACKGROUND: Joubert syndrome (JBTS) is a rare neurodevelopmental disorder with marked phenotypic variability and genetic heterogeneity. Homozygous or compound heterozygous mutations in the KIAA0586 gene on chromosome 14q23 are known to be associated with JBTS-23. The frameshift variant c.428delG is the most frequent KIAA0586 variant reported in JBTS-23; yet, homozygosity of this variant was observed in two patients with JBTS-23. However, homozygosity of the c.428delG variant was recently reported as well in one healthy individual. OBJECTIVE: To clarify whether the frameshift variant c.428delG in KIAA0586 is pathogenic in the homozygous state. METHODS: Whole-exome sequencing as well as RNA analysis were performed. RESULTS: We identified biallelic mutations, including the variant c.428delG and a splice site variant c.1413-1G>C, in KIAA0586 in two siblings with clinical and MRI features of JBTS. The c.1413-1G>C variant was inherited from the healthy father. The c.428delG variant was found in the healthy mother in a homozygous state in blood lymphocytes, hair root cells and buccal epithelial cells. RNA analysis revealed that the transcript harbouring the c.428delG variant was expressed in blood cells from the healthy mother, indicating that transcripts harbouring this variant elude the mechanism of nonsense-mediated mRNA decay. CONCLUSION: Considering this and the high allele frequency of 0.003117 in the gnomAD database, we conclude that c.428delG represents a JBTS disease-causing variant only if present in compound heterozygous state with a more severe KIAA0586 variant, but not in a homozygous situation.


Assuntos
Anormalidades Múltiplas/diagnóstico , Anormalidades Múltiplas/genética , Alelos , Proteínas de Ciclo Celular/genética , Cerebelo/anormalidades , Anormalidades do Olho/diagnóstico , Anormalidades do Olho/genética , Homozigoto , Doenças Renais Císticas/diagnóstico , Doenças Renais Císticas/genética , Fenótipo , Retina/anormalidades , Deleção de Sequência , Adulto , Análise Mutacional de DNA , Feminino , Humanos , Imageamento por Ressonância Magnética , Masculino , Pessoa de Meia-Idade , Dente Molar/patologia
6.
Am J Med Genet C Semin Med Genet ; 175(4): 478-486, 2017 12.
Artigo em Inglês | MEDLINE | ID: mdl-29082625

RESUMO

Neural crest cells are highly migratory pluripotent cells that give rise to diverse derivatives including cartilage, bone, smooth muscle, pigment, and endocrine cells as well as neurons and glia. Abnormalities in neural crest-derived tissues contribute to the etiology of CHARGE syndrome, a complex malformation disorder that encompasses clinical symptoms like coloboma, heart defects, atresia of the choanae, retarded growth and development, genital hypoplasia, ear anomalies, and deafness. Mutations in the chromodomain helicase DNA-binding protein 7 (CHD7) gene are causative of CHARGE syndrome and loss-of-function data in different model systems have firmly established a role of CHD7 in neural crest development. Here, we will summarize our current understanding of the function of CHD7 in neural crest development and discuss possible links of CHARGE syndrome to other developmental disorders.


Assuntos
Síndrome CHARGE/diagnóstico , Síndrome CHARGE/etiologia , Crista Neural/anormalidades , Fenótipo , Trifosfato de Adenosina/metabolismo , Animais , Síndrome CHARGE/metabolismo , Montagem e Desmontagem da Cromatina , DNA Helicases/genética , DNA Helicases/metabolismo , Proteínas de Ligação a DNA/genética , Proteínas de Ligação a DNA/metabolismo , Modelos Animais de Doenças , Humanos , Complexos Multiproteicos/metabolismo , Mutação , Ligação Proteica
7.
Hum Mol Genet ; 23(16): 4396-405, 2014 Aug 15.
Artigo em Inglês | MEDLINE | ID: mdl-24705355

RESUMO

CHARGE syndrome is a complex developmental disorder caused by mutations in the chromodomain helicase DNA-binding gene CHD7. Kabuki syndrome, another developmental disorder, is characterized by typical facial features in combination with developmental delay, short stature, prominent digit pads and visceral abnormalities. Mutations in the KMT2D gene, which encodes a H3K4 histone methyltransferase, are the major cause of Kabuki syndrome. Here, we report a patient, who was initially diagnosed with CHARGE syndrome based on the spectrum of inner organ malformations like choanal hypoplasia, heart defect, anal atresia, vision problems and conductive hearing impairment. While sequencing and MLPA analysis of all coding exons of CHD7 revealed no pathogenic mutation, sequence analysis of the KMT2D gene identified the heterozygous de novo nonsense mutation c.5263C > T (p.Gln1755*). Thus, our patient was diagnosed with Kabuki syndrome. By using co-immunoprecipitation, immunohistochemistry and direct yeast two hybrid assays, we could show that, like KMT2D, CHD7 interacts with members of the WAR complex, namely WDR5, ASH2L and RbBP5. We therefore propose that CHD7 and KMT2D function in the same chromatin modification machinery, thus pointing out a mechanistic connection, and presenting a probable explanation for the phenotypic overlap between Kabuki and CHARGE syndromes.


Assuntos
Anormalidades Múltiplas/metabolismo , Síndrome CHARGE/metabolismo , DNA Helicases/metabolismo , Proteínas de Ligação a DNA/metabolismo , Face/anormalidades , Doenças Hematológicas/metabolismo , Proteínas de Neoplasias/metabolismo , Doenças Vestibulares/metabolismo , Anormalidades Múltiplas/genética , Anormalidades Múltiplas/patologia , Síndrome CHARGE/genética , Síndrome CHARGE/patologia , Criança , DNA Helicases/genética , Proteínas de Ligação a DNA/genética , Face/patologia , Células HeLa/citologia , Doenças Hematológicas/genética , Doenças Hematológicas/patologia , Humanos , Peptídeos e Proteínas de Sinalização Intracelular , Masculino , Mutação , Proteínas de Neoplasias/genética , Proteínas Nucleares/metabolismo , Fenótipo , Proteínas/metabolismo , Fatores de Transcrição/metabolismo , Doenças Vestibulares/genética , Doenças Vestibulares/patologia
8.
Hum Mutat ; 36(8): 787-96, 2015 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-25952305

RESUMO

Noonan syndrome (NS) is a relatively common developmental disorder with a pleomorphic phenotype. Mutations causing NS alter genes encoding proteins involved in the RAS-MAPK pathway. We and others identified Casitas B-lineage lymphoma proto-oncogene (CBL), which encodes an E3-ubiquitin ligase acting as a tumor suppressor in myeloid malignancies, as a disease gene underlying a condition clinically related to NS. Here, we further explored the spectrum of germline CBL mutations and their associated phenotype. CBL mutation scanning performed on 349 affected subjects with features overlapping NS and no mutation in NS genes allowed the identification of five different variants with pathological significance. Among them, two splice-site changes, one in-frame deletion, and one missense mutation affected the RING domain and/or the adjacent linker region, overlapping cancer-associated defects. A novel nonsense mutation generating a v-Cbl-like protein able to enhance signal flow through RAS was also identified. Genotype-phenotype correlation analysis performed on available records indicated that germline CBL mutations cause a variable phenotype characterized by a relatively high frequency of neurological features, predisposition to juvenile myelomonocytic leukemia, and low prevalence of cardiac defects, reduced growth, and cryptorchidism. Finally, we excluded a major contribution of two additional members of the CBL family, CBLB and CBLC, to NS and related disorders.


Assuntos
Variação Genética , Mutação em Linhagem Germinativa , Proteínas Proto-Oncogênicas c-cbl/genética , Pré-Escolar , Feminino , Estudos de Associação Genética , Humanos , Masculino , Síndrome de Noonan/genética , Síndrome de Noonan/fisiopatologia , Proto-Oncogene Mas , Proteínas Proto-Oncogênicas c-cbl/metabolismo
9.
Hum Genet ; 133(8): 997-1009, 2014 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-24728844

RESUMO

Heterozygous loss of function mutations in CHD7 (chromodomain helicase DNA-binding protein 7) lead to CHARGE syndrome, a complex developmental disorder affecting craniofacial structures, cranial nerves and several organ systems. Recently, it was demonstrated that CHD7 is essential for the formation of multipotent migratory neural crest cells, which migrate from the neural tube to many regions of the embryo, where they differentiate into various tissues including craniofacial and heart structures. So far, only few CHD7 target genes involved in neural crest cell development have been identified and the role of CHD7 in neural crest cell guidance and the regulation of mesenchymal-epithelial transition are unknown. Therefore, we undertook a genome-wide microarray expression analysis on wild-type and CHD7 deficient (Chd7 (Whi/+) and Chd7 (Whi/Whi)) mouse embryos at day 9.5, a time point of neural crest cell migration. We identified 98 differentially expressed genes between wild-type and Chd7 (Whi/Whi) embryos. Interestingly, many misregulated genes are involved in neural crest cell and axon guidance such as semaphorins and ephrin receptors. By performing knockdown experiments for Chd7 in Xenopus laevis embryos, we found abnormalities in the expression pattern of Sema3a, a protein involved in the pathogenesis of Kallmann syndrome, in vivo. In addition, we detected non-synonymous SEMA3A variations in 3 out of 45 CHD7-negative CHARGE patients. In summary, we discovered for the first time that Chd7 regulates genes involved in neural crest cell guidance, demonstrating a new aspect in the pathogenesis of CHARGE syndrome. Furthermore, we showed for Sema3a a conserved regulatory mechanism across different species, highlighting its significance during development. Although we postulated that the non-synonymous SEMA3A variants which we found in CHD7-negative CHARGE patients alone are not sufficient to produce the phenotype, we suggest an important modifier role for SEMA3A in the pathogenesis of this multiple malformation syndrome.


Assuntos
Anormalidades Múltiplas/genética , Biomarcadores/metabolismo , Síndrome CHARGE/genética , Proteínas de Ligação a DNA/fisiologia , Regulação da Expressão Gênica no Desenvolvimento , Mutação/genética , Animais , Western Blotting , Síndrome CHARGE/patologia , Feminino , Perfilação da Expressão Gênica , Humanos , Hibridização In Situ , Masculino , Camundongos , Camundongos Knockout , Crista Neural , Análise de Sequência com Séries de Oligonucleotídeos , Fenótipo , RNA Mensageiro/genética , Reação em Cadeia da Polimerase em Tempo Real , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Xenopus laevis/crescimento & desenvolvimento , Xenopus laevis/metabolismo
10.
Dis Model Mech ; 17(6)2024 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-38501224

RESUMO

De novo truncating variants in fibrosin-like 1 (FBRSL1), a member of the AUTS2 gene family, cause a disability syndrome, including organ malformations such as heart defects. Here, we use Xenopus laevis to investigate whether Fbrsl1 plays a role in heart development. Xenopus laevis fbrsl1 is expressed in tissues relevant for heart development, and morpholino-mediated knockdown of Fbrsl1 results in severely hypoplastic hearts. Our data suggest that Fbrsl1 is required for the development of the first heart field, which contributes to the ventricle and the atria, but not for the second heart field, which gives rise to the outflow tract. The morphant heart phenotype could be rescued using a human N-terminal FBRSL1 isoform that contains an alternative exon, but lacks the AUTS2 domain. N-terminal isoforms carrying patient variants failed to rescue. Interestingly, a long human FBRSL1 isoform, harboring the AUTS2 domain, also did not rescue the morphant heart defects. Thus, our data suggest that different FBRSL1 isoforms may have distinct functions and that only the short N-terminal isoform, appears to be critical for heart development.


Assuntos
Cardiopatias Congênitas , Coração , Proteínas de Xenopus , Xenopus laevis , Animais , Humanos , Regulação da Expressão Gênica no Desenvolvimento , Técnicas de Silenciamento de Genes , Coração/embriologia , Cardiopatias Congênitas/genética , Cardiopatias Congênitas/patologia , Fenótipo , Isoformas de Proteínas/metabolismo , Isoformas de Proteínas/genética , Xenopus laevis/embriologia , Proteínas de Xenopus/metabolismo , Proteínas de Xenopus/genética
11.
Hum Mol Genet ; 19(14): 2858-66, 2010 Jul 15.
Artigo em Inglês | MEDLINE | ID: mdl-20453063

RESUMO

CHARGE syndrome is an autosomal dominant disorder caused in about two-third of cases by mutations in the CHD7 gene. For other genetic diseases e.g. hereditary spastic paraplegia, it was shown that interacting partners are involved in the underlying cause of the disease. These data encouraged us to search for CHD7 binding partners by a yeast two-hybrid library screen and CHD8 was identified as an interacting partner. The result was confirmed by a direct yeast two-hybrid analysis, co-immunoprecipitation studies and by a bimolecular fluorescence complementation assay. To investigate the function of CHD7 missense mutations in the CHD7-CHD8 interacting area on the binding capacity of both proteins, we included three known missense mutations (p.His2096Arg, p.Val2102Ile and p.Gly2108Arg) and one newly identified missense mutation (p.Trp2091Arg) in the CHD7 gene and performed both direct yeast two-hybrid and co-immunoprecipitation studies. In the direct yeast two-hybrid system, the CHD7-CHD8 interaction was disrupted by the missense mutations p.Trp2091Arg, p.His2096Arg and p.Gly2108Arg, whereas in the co-immunoprecipitation studies disruption of the CHD7-CHD8 interaction by the mutations could not be observed. The results lead to the hypothesis that CHD7 and CHD8 proteins are interacting directly and indirectly via additional linker proteins. Disruption of the direct CHD7-CHD8 interaction might change the conformation of a putative large CHD7-CHD8 complex and could be a disease mechanism in CHARGE syndrome.


Assuntos
Anormalidades Múltiplas/genética , DNA Helicases/genética , DNA Helicases/metabolismo , Proteínas de Ligação a DNA/genética , Proteínas de Ligação a DNA/metabolismo , Fatores de Transcrição/metabolismo , Anormalidades Múltiplas/metabolismo , Atresia das Cóanas/complicações , Atresia das Cóanas/genética , Atresia das Cóanas/metabolismo , Coloboma/complicações , Coloboma/genética , Coloboma/metabolismo , Surdez/complicações , Surdez/congênito , Surdez/genética , Surdez/metabolismo , Deficiências do Desenvolvimento/complicações , Deficiências do Desenvolvimento/genética , Deficiências do Desenvolvimento/metabolismo , Orelha/anormalidades , Células HeLa , Cardiopatias Congênitas/complicações , Cardiopatias Congênitas/genética , Cardiopatias Congênitas/metabolismo , Humanos , Mutação/fisiologia , Ligação Proteica/genética , Domínios e Motivos de Interação entre Proteínas/genética , Domínios e Motivos de Interação entre Proteínas/fisiologia , Infantilismo Sexual/complicações , Infantilismo Sexual/genética , Infantilismo Sexual/metabolismo , Síndrome , Transfecção , Técnicas do Sistema de Duplo-Híbrido
12.
Am J Med Genet A ; 158A(3): 652-8, 2012 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-22315187

RESUMO

Noonan syndrome (NS) is a common autosomal dominant condition characterized by short stature, congenital heart defects, and dysmorphic facial features caused in approximately 50% of cases by missense mutations in the PTPN11 gene. NS patients are predisposed to malignancies including myeloproliferative disorders or leukemias. We report a female NS patient carrying a PTPN11 germline mutation c.417 G > C (p.E139D), who developed in her second year of life an acute lymphoblastic leukemia (ALL) and after remission, she developed at 4 years of age a juvenile myelomonocytic leukemia (JMML). Molecular genetic analysis of lymphoblastic blasts at the time of the ALL diagnosis revealed the germline mutation in a heterozygous state, while in the myelomonocytic blasts occurring with JMML diagnosis, the mutation p.E139D was found in a homozygous state due to a uniparental disomy (UPD). These findings lead to the suggestion that the pathogenesis of ALL and JMML in our patient is due to different mechanisms including somatically acquired secondary chromosomal abnormalities.


Assuntos
Mutação em Linhagem Germinativa , Leucemia Mielomonocítica Juvenil/complicações , Síndrome de Noonan/genética , Leucemia-Linfoma Linfoblástico de Células Precursoras/complicações , Proteína Tirosina Fosfatase não Receptora Tipo 11/genética , Hibridização Genômica Comparativa , Feminino , Heterozigoto , Humanos , Lactente , Leucemia Mielomonocítica Juvenil/genética , Síndrome de Noonan/complicações , Leucemia-Linfoma Linfoblástico de Células Precursoras/genética
13.
Front Neurol ; 13: 893605, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-35928135

RESUMO

Background: Benefits and challenges resulting from advances in genetic diagnostics are two sides of the same coin. Facilitation of a correct and timely diagnosis is paralleled by challenges in interpretation of variants of unknown significance (VUS). Focusing on an individual VUS-re-classification pipeline, this study offers a diagnostic approach for clinically suspected hereditary muscular dystrophy by combining the expertise of an interdisciplinary team. Methods: In a multi-step approach, a thorough phenotype assessment including clinical examination, laboratory work, muscle MRI and histopathological evaluation of muscle was performed in combination with advanced Next Generation Sequencing (NGS). Different in-silico tools and prediction programs like Alamut, SIFT, Polyphen, MutationTaster and M-Cap as well as 3D- modeling of protein structure and RNA-sequencing were employed to determine clinical significance of the LAMA2 variants. Results: Two previously unknown sequence alterations in LAMA2 were detected, a missense variant was classified initially according to ACMG guidelines as a VUS (class 3) whereas a second splice site variant was deemed as likely pathogenic (class 4). Pathogenicity of the splice site variant was confirmed by mRNA sequencing and nonsense mediated decay (NMD) was detected. Combination of the detected variants could be associated to the LGMDR23-phenotype based on the MRI matching and literature research. Discussion: Two novel variants in LAMA2 associated with LGMDR23-phenotype are described. This study illustrates challenges of the genetic findings due to their VUS classification and elucidates how individualized diagnostic procedure has contributed to the accurate diagnosis in the spectrum of LGMD.

14.
Front Cell Dev Biol ; 9: 779009, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34805182

RESUMO

Truncating variants in specific exons of Fibrosin-like protein 1 (FBRSL1) were recently reported to cause a novel malformation and intellectual disability syndrome. The clinical spectrum includes microcephaly, facial dysmorphism, cleft palate, skin creases, skeletal anomalies and contractures, postnatal growth retardation, global developmental delay as well as respiratory problems, hearing impairment and heart defects. The function of FBRSL1 is largely unknown, but pathogenic variants in the FBRSL1 paralog Autism Susceptibility Candidate 2 (AUTS2) are causative for an intellectual disability syndrome with microcephaly (AUTS2 syndrome). Some patients with AUTS2 syndrome also show additional symptoms like heart defects and contractures overlapping with the phenotype presented by patients with FBRSL1 mutations. For AUTS2, a dual function, depending on different isoforms, was described and suggested for FBRSL1. Both, nuclear FBRSL1 and AUTS2 are components of the Polycomb subcomplexes PRC1.3 and PRC1.5. These complexes have essential roles in developmental processes, cellular differentiation and proliferation by regulating gene expression via histone modification. In addition, cytoplasmic AUTS2 controls neural development, neuronal migration and neurite extension by regulating the cytoskeleton. Here, we review recent data on FBRSL1 in respect to previously published data on AUTS2 to gain further insights into its molecular function, its role in development as well as its impact on human genetics.

15.
Am J Med Genet A ; 152A(8): 1960-6, 2010 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-20602484

RESUMO

The facial photographs of 81 individuals with Noonan syndrome, from infancy to adulthood, have been evaluated by two dysmorphologists (JA and MZ), each of whom has considerable experience with disorders of the Ras/MAPK pathway. Thirty-two of this cohort have PTPN11 mutations, 21 SOS1 mutations, 11 RAF1 mutations, and 17 KRAS mutations. The facial appearance of each person was judged to be typical of Noonan syndrome or atypical. In each gene category both typical and unusual faces were found. We determined that some individuals with mutations in the most commonly affected gene, PTPN11, which is correlated with the cardinal physical features, may have a quite atypical face. Conversely, some individuals with KRAS mutations, which may be associated with a less characteristic intellectual phenotype and a resemblance to Costello and cardio-facio-cutaneous syndromes, can have a very typical face. Thus, the facial phenotype, alone, is insufficient to predict the genotype, but certain facial features may facilitate an educated guess in some cases.


Assuntos
Anormalidades Múltiplas , Mutação/genética , Síndrome de Noonan/genética , Proteína Tirosina Fosfatase não Receptora Tipo 11/genética , Proteínas Proto-Oncogênicas c-raf/genética , Proteínas Proto-Oncogênicas/genética , Proteína SOS1/genética , Proteínas ras/genética , Adolescente , Adulto , Criança , Pré-Escolar , Feminino , Genótipo , Humanos , Lactente , Masculino , Síndrome de Noonan/diagnóstico , Fenótipo , Proteínas Proto-Oncogênicas p21(ras) , Síndrome , Adulto Jovem
16.
Mol Syndromol ; 11(1): 30-37, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-32256299

RESUMO

Multiple congenital anomalies-hypotonia-seizures syndrome 2 (MCAHS2) is a rare disease caused by mutations in the X chromosomal PIGA gene. Clinically it is characterized by early-onset epilepsy, hypotonia, dysmorphic features, and variable congenital anomalies. PIGA codes for the phosphatidylinositol glycan-class A protein, which forms a subunit of an enzymatic complex involved in glycophosphatidylinositol (GPI) biosynthesis. We present a new case of MCAHS2 and perform a comprehensive review of the available literature to delineate the phenotypical traits associated with germline PIGA mutations. Furthermore, we provide functional evidence of pathogenicity of the novel missense mutation, c.154C>T; (p.His52Tyr), in the PIGA gene causative of MCAHS2 in our patient. By flow cytometry, we observed reduced expression of GPI-anchored surface proteins in patient granulocytes compared to control samples, proving GPI-biogenesis impairment. The patient's severe epilepsy with several daily attacks was refractory to treatment, but the frequency of seizures reduced temporarily under triple therapy with perampanel, rufinamide and vigabatrin. Our study delineates the known MCAHS2 phenotype and discusses challenges of diagnosis and clinical management in this complex, rare disease. Furthermore, we present a novel mutation with functional evidence of pathogenicity.

17.
J Hum Genet ; 54(6): 331-4, 2009 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-19373259

RESUMO

Transcobalamin II (TC II) is a plasma transport protein for cobalamin. TC II deficiency can lead to infant megaloblastic anemia, failure to thrive and to neurological complications. This report describes the genetic work-up of three patients who presented in early infancy. Initially, genomic investigations did not reveal the definite genetic diagnosis in the two index patients. However, analysis of cDNA from skin fibroblasts revealed a homozygous deletion of exon 7 of the TC II gene caused by the mutation c.940+303_c.1106+746del2152insCTGG (r.941_1105del; p.fs326X) in one patient. The other patients were siblings and both affected by an insertion of 87 bp on the transcript which was caused by the homozygous mutation c.580+624A>T (r.580ins87; p.fs209X). Additional experiments showed that cDNA from lymphocytes could have been used also for the genetic work-up. This report shows that the use of cDNA from skin fibroblasts or peripheral lymphocytes facilitates genetic investigations of suspected TC II deficiency and helps to avoid false-negative DNA analysis.


Assuntos
Anemia Megaloblástica/diagnóstico , DNA Complementar/genética , RNA/genética , Transcobalaminas/deficiência , Transcobalaminas/genética , Anemia Megaloblástica/genética , Criança , DNA Complementar/metabolismo , Feminino , Fibroblastos/metabolismo , Seguimentos , Humanos , Recém-Nascido , Linfócitos/metabolismo , Masculino , Prognóstico , RNA/metabolismo , Pele/citologia , Pele/metabolismo
18.
Hum Mutat ; 29(10): 1222-7, 2008 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-18473344

RESUMO

Mild citrullinemia is an allelic variant of classical citrullinemia type I also caused by deficiency of the urea cycle enzyme argininosuccinate synthetase (ASS). Affected patients comprise a biochemical but no clinical phenotype. However, there is no reliable parameter allowing conclusions regarding the course of the disorder or its type of manifestation. The aim of this study was to test the importance of varying levels of ASS residual activities for the severity at diagnosis. Bacterial in vitro expression studies allowed the enzymatic analysis of purified wild-type and the mutant ASS proteins p.Ala118Thr (c.352G>A), p.Trp179Arg (c.535T>C), p.Val263Met (c.787G>A), p.Arg265Cys (c.793C>T), p.Met302Val (c.904A>G), p.Gly324Ser (c.970G>A), p.Gly362Val (c.1085G>T), and p.Gly390Arg (c.1168G>A). In the chosen system, classical mutations do not show any significant enzymatic activity, whereas mutations associated with a mild course yield significant ASS activity levels. The mutation p.Ala118Thr (c.352G>A) impresses by a high residual activity (62%) but a severe reduction of affinity toward the substrates citrulline and aspartate. This mutation was identified in a hitherto healthy female adult with no history of known citrullinemia who had died during the postpartum period from hyperammonemic coma. The results of this study suggest that even a high level of residual ASS activity is not a reliable prognostic marker for an uneventful clinical course. Determination of ASS residual activities, therefore, cannot help in anticipating the risk of metabolic derangement. This study should guide clinicians as well as patients with mild citrullinemia toward a lifelong awareness of the disorder.


Assuntos
Argininossuccinato Sintase/genética , Citrulinemia/genética , Adulto , Argininossuccinato Sintase/metabolismo , Citrulinemia/diagnóstico , DNA Complementar/metabolismo , Escherichia coli/genética , Escherichia coli/metabolismo , Feminino , Expressão Gênica , Variação Genética , Genótipo , Humanos , Mutação
19.
J Med Genet ; 44(10): 651-6, 2007 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-17586837

RESUMO

BACKGROUND: Heterozygous gain-of-function mutations in various genes encoding proteins of the Ras-MAPK signalling cascade have been identified as the genetic basis of Noonan syndrome (NS) and cardio-facio-cutaneous syndrome (CFCS). Mutations of SOS1, the gene encoding a guanine nucleotide exchange factor for Ras, have been the most recent discoveries in patients with NS, but this gene has not been studied in patients with CFCS. METHODS AND RESULTS: We investigated SOS1 in a large cohort of patients with disorders of the NS-CFCS spectrum, who had previously tested negative for mutations in PTPN11, KRAS, BRAF, MEK1 and MEK2. Missense mutations of SOS1 were discovered in 28% of patients with NS. In contrast, none of the patients classified as having CFCS was found to carry a pathogenic sequence change in this gene. CONCLUSION: We have confirmed SOS1 as the second major gene for NS. Patients carrying mutations in this gene have a distinctive phenotype with frequent ectodermal anomalies such as keratosis pilaris and curly hair. However, the clinical picture associated with SOS1 mutations is different from that of CFCS. These findings corroborate that, despite being caused by gain-of-function mutations in molecules belonging to the same pathway, NS and CFCS scarcely overlap genotypically.


Assuntos
Cardiopatias/genética , Síndrome de Noonan/genética , Proteína SOS1/genética , Proteína SOS1/fisiologia , Dermatopatias/genética , Síndrome , Sequência de Aminoácidos , Estatura , Constrição Patológica , Feminino , Cardiopatias/congênito , Heterozigoto , Humanos , Masculino , Dados de Sequência Molecular , Homologia de Sequência de Aminoácidos , Fatores ras de Troca de Nucleotídeo Guanina/metabolismo
20.
Mol Cytogenet ; 11: 62, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-30619508

RESUMO

BACKGROUND: Down syndrome, typically caused by trisomy 21, may also be associated by duplications of the Down syndrome critical region (DSCR) on chromosome 21q22. However, patients with small duplications of DSCR without accompanying deletions have rarely been reported. CASE PRESENTATION: Here we report a 5½-year-old boy with clinical features of Down syndrome including distinct craniofacial dysmorphism and sandal gaps as well as developmental delay. Conventional karyotype was normal, whereas interphase FISH analysis revealed three signals for DSCR in approximately 40% of lymphocytes and 80% of buccal mucosa cells. Array-CGH analysis confirmed a 2.56 Mb duplication of chromosome 21q22.13q22.2 encompassing DYRK1A. CONCLUSION: This presents one of the smallest duplications within DSCR leading to a Down syndrome phenotype. Since the dosage sensitive gene DYRK1A is the only duplicated candidate DSCR gene in our patient, this finding supports the hypothesis that DYRK1A contributes to dysmorphic and intellectual features of Down syndrome even in a mosaic state.

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