RESUMEN
Kabuki syndrome (KS) is a rare congenital disorder commonly complicated by humoral immunodeficiency. Patients with KS present with mutation in the histone-lysine N-methyltransferase 2D (KMT2D) gene. Although various KMT2D mutations are often identified in lymphoma and leukemia, those encountered in aplastic anemia (AA) are limited. Herein, we present the case of a 45-year-old Japanese man who developed severe pancytopenia and hypogammaglobulinemia. He did not present with any evident malformations, intellectual disability, or detectable levels of autoantibodies. However, B-cell development was impaired. Therefore, a diagnosis of very severe AA due to a hypoplastic marrow, which did not respond to granulocyte colony-stimulating factor, was made. The patient received umbilical cord blood transplantation but died from a Pseudomonas infection before neutrophil engraftment. Trio whole-exome sequencing revealed a novel missense heterozygous mutation c.15959G >A (p.R5320H) in exon 50 of the KMT2D gene. Moreover, Sanger sequencing of peripheral blood and bone marrow mononuclear cells and a skin biopsy specimen obtained from this patient identified this heterozygous mutation, suggesting that de novo mutation associated with KS occurred in the early embryonic development. Our case showed a novel association between KS mutation and adult-onset AA.
Asunto(s)
Anomalías Múltiples/genética , Anemia Aplásica/genética , Proteínas de Unión al ADN/genética , Cara/anomalías , Enfermedades Hematológicas/genética , Mutación , Proteínas de Neoplasias/genética , Enfermedades Vestibulares/genética , Anomalías Múltiples/enzimología , Anomalías Múltiples/terapia , Aloinjertos , Anemia Aplásica/enzimología , Anemia Aplásica/terapia , Trasplante de Células Madre de Sangre del Cordón Umbilical , Resultado Fatal , Enfermedades Hematológicas/enzimología , Enfermedades Hematológicas/terapia , Humanos , Masculino , Persona de Mediana Edad , Gravedad del Paciente , Infecciones por Pseudomonas , Enfermedades Vestibulares/enzimología , Enfermedades Vestibulares/terapiaRESUMEN
Kabuki syndrome (KS) is a congenital craniofacial disorder resulting from mutations in the KMT2D histone methylase (KS1) or the UTX histone demethylase (KS2). With small cohorts of KS2 patients, it is not clear whether differences exist in clinical manifestations relative to KS1. We mutated KMT2D in neural crest cells (NCCs) to study cellular and molecular functions in craniofacial development with respect to UTX. Similar to UTX, KMT2D NCC knockout mice demonstrate hypoplasia with reductions in frontonasal bone lengths. We have traced the onset of KMT2D and UTX mutant NCC frontal dysfunction to a stage of altered osteochondral progenitor differentiation. KMT2D NCC loss-of-function does exhibit unique phenotypes distinct from UTX mutation, including fully penetrant cleft palate, mandible hypoplasia and deficits in cranial base ossification. KMT2D mutant NCCs lead to defective secondary palatal shelf elevation with reduced expression of extracellular matrix components. KMT2D mutant chondrocytes in the cranial base fail to properly differentiate, leading to defective endochondral ossification. We conclude that KMT2D is required for appropriate cranial NCC differentiation and KMT2D-specific phenotypes may underlie differences between Kabuki syndrome subtypes.
Asunto(s)
Anomalías Múltiples/enzimología , Anomalías Múltiples/patología , Diferenciación Celular , Cara/anomalías , Enfermedades Hematológicas/enzimología , Enfermedades Hematológicas/patología , N-Metiltransferasa de Histona-Lisina/metabolismo , Proteína de la Leucemia Mieloide-Linfoide/metabolismo , Cresta Neural/enzimología , Cresta Neural/patología , Enfermedades Vestibulares/enzimología , Enfermedades Vestibulares/patología , Alelos , Animales , Linaje de la Célula , Movimiento Celular , Condrocitos/patología , Cara/patología , Ratones Endogámicos C57BL , Ratones Noqueados , Morfogénesis , Mutación/genética , Osteogénesis , Hueso Paladar/embriología , Hueso Paladar/metabolismo , Hueso Paladar/patología , Fenotipo , Cráneo/patologíaRESUMEN
Kabuki syndrome is an autosomal dominant developmental disorder with high similarities to CHARGE syndrome. It is characterized by a typical facial gestalt in combination with short stature, intellectual disability, skeletal findings and additional features like cardiac and urogenital malformations, cleft palate, hearing loss and ophthalmological anomalies. The major cause of Kabuki syndrome are mutations in KMT2D, a gene encoding a histone H3 lysine 4 (H3K4) methyltransferase belonging to the group of chromatin modifiers. Here we provide evidence that Kabuki syndrome is a neurocrestopathy, by showing that Kmt2d loss-of-function inhibits specific steps of neural crest (NC) development. Using the Xenopus model system, we find that Kmt2d loss-of-function recapitulates major features of Kabuki syndrome including severe craniofacial malformations. A detailed marker analysis revealed defects in NC formation as well as migration. Transplantation experiments confirm that Kmt2d function is required in NC cells. Furthermore, analyzing in vivo and in vitro NC migration behavior demonstrates that Kmt2d is necessary for cell dispersion but not protrusion formation of migrating NC cells. Importantly, Kmt2d knockdown correlates with a decrease in H3K4 monomethylation and H3K27 acetylation supporting a role of Kmt2d in the transcriptional activation of target genes. Consistently, using a candidate approach, we find that Kmt2d loss-of-function inhibits Xenopus Sema3F expression, and overexpression of Sema3F can partially rescue Kmt2d loss-of-function defects. Taken together, our data reveal novel functions of Kmt2d in multiple steps of NC development and support the hypothesis that major features of Kabuki syndrome are caused by defects in NC development.
Asunto(s)
Anomalías Múltiples/enzimología , Cara/anomalías , Enfermedades Hematológicas/enzimología , N-Metiltransferasa de Histona-Lisina/genética , N-Metiltransferasa de Histona-Lisina/metabolismo , Cresta Neural/metabolismo , Enfermedades Vestibulares/enzimología , Proteínas de Xenopus/genética , Proteínas de Xenopus/metabolismo , Anomalías Múltiples/genética , Anomalías Múltiples/metabolismo , Anomalías Múltiples/patología , Acetilación , Animales , Movimiento Celular/genética , Proteínas de Unión al ADN/genética , Proteínas de Unión al ADN/metabolismo , Cara/patología , Enfermedades Hematológicas/genética , Enfermedades Hematológicas/metabolismo , Enfermedades Hematológicas/patología , Histonas/metabolismo , Mutación con Pérdida de Función , Metilación , Mutación , Proteínas de Neoplasias/genética , Proteínas de Neoplasias/metabolismo , Cresta Neural/enzimología , Cresta Neural/patología , Placa Neural/crecimiento & desarrollo , Placa Neural/metabolismo , Placa Neural/patología , Semaforinas/genética , Semaforinas/metabolismo , Enfermedades Vestibulares/genética , Enfermedades Vestibulares/metabolismo , Enfermedades Vestibulares/patología , Xenopus/embriología , Xenopus/genética , Xenopus/metabolismo , Proteínas de Xenopus/fisiologíaRESUMEN
Kabuki syndrome is a rare autosomal dominant condition characterized by facial features, various organs malformations, postnatal growth deficiency and intellectual disability. The discovery of frequent germline mutations in the histone methyltransferase KMT2D and the demethylase KDM6A revealed a causative role for histone modifiers in this disease. However, the role of missense mutations has remained unexplored. Here, we expanded the mutation spectrum of KMT2D and KDM6A in KS by identifying 37 new KMT2D sequence variants. Moreover, we functionally dissected 14 KMT2D missense variants, by investigating their impact on the protein enzymatic activity and the binding to members of the WRAD complex. We demonstrate impaired H3K4 methyltransferase activity in 9 of the 14 mutant alleles and show that this reduced activity is due in part to disruption of protein complex formation. These findings have relevant implications for diagnostic and counseling purposes in this disease.
Asunto(s)
Anomalías Múltiples/genética , Proteínas de Unión al ADN/genética , Cara/anomalías , Enfermedades Hematológicas/genética , Mutación Missense , Proteínas de Neoplasias/genética , Enfermedades Vestibulares/genética , Anomalías Múltiples/enzimología , Simulación por Computador , Proteínas de Unión al ADN/metabolismo , Enfermedades Hematológicas/enzimología , Histona Demetilasas/genética , Humanos , Modelos Moleculares , Mutación , Proteínas de Neoplasias/metabolismo , Proteínas Nucleares/genética , Conformación Proteica , Análisis de Secuencia de Proteína , Enfermedades Vestibulares/enzimologíaRESUMEN
In 2007, the Ubiquitously Transcribed Tetratricopeptide Repeat on chromosome X (UTX) was identified as a histone demethylase that specifically targets di- and tri-methyl groups on lysine 27 of histone H3 (H3K27me2/3). Since then, UTX has been proven essential during normal development, as it is critically required for correct reprogramming, embryonic development and tissue-specific differentiation. UTX is a member of the MLL2 H3K4 methyltransferase complex and its catalytic activity has been linked to regulation of HOX and RB transcriptional networks. In addition, an H3K27me2/3 demethylase independent function for UTX was uncovered in promoting general chromatin remodeling in concert with the BRG1-containing SWI/SNF remodeling complex. Constitutional inactivation of UTX causes a specific hereditary disorder called the Kabuki syndrome, whereas somatic loss of UTX has been reported in a variety of human cancers. Here, we compile the breakthrough discoveries made from the first disclosure of UTX as a histone demethylase till the identification of disease-related UTX mutations and specific UTX inhibitors.
Asunto(s)
Anomalías Múltiples/enzimología , Desarrollo Embrionario , Cara/anomalías , Enfermedades Hematológicas/enzimología , Histona Demetilasas/metabolismo , Histonas/metabolismo , Neoplasias/enzimología , Proteínas Nucleares/metabolismo , Enfermedades Vestibulares/enzimología , Animales , Reprogramación Celular , Células Madre Embrionarias/enzimología , Genes Supresores de Tumor , Histona Demetilasas/antagonistas & inhibidores , Humanos , Proteínas Nucleares/antagonistas & inhibidores , Inactivación del Cromosoma XRESUMEN
BACKGROUND: Caspase-3 is one of the most downstream enzymes activated in the apoptotic pathway. In caspase-3 deficient mice, loss of cochlear hair cells and spiral ganglion cells coincide closely with hearing loss. In contrast with the auditory system, details of the vestibular phenotype have not been characterized. Here we report the vestibular phenotype and inner ear anatomy in the caspase-3 deficient (Casp3(-/-)) mouse strain. RESULTS: Average ABR thresholds of Casp3(-/-) mice were significantly elevated (P < 0.05) compared to Casp3(+/-) mice and Casp3(+/+) mice at 3 months of age. In DPOAE testing, distortion product 2F1-F2 was significantly decreased (P < 0.05) in Casp3(-/-) mice, whereas Casp3(+/-) and Casp3(+/+) mice showed normal and comparable values to each other. Casp3(-/-) mice were hyperactive and exhibited circling behavior when excited. In lateral canal VOR testing, Casp3(-/-) mice had minimal response to any of the stimuli tested, whereas Casp3(+/-) mice had an intermediate response compared to Casp3(+/+) mice. Inner ear anatomical and histological analysis revealed gross hypomorphism of the vestibular organs, in which the main site was the anterior semicircular canal. Hair cell numbers in the anterior- and lateral crista, and utricle were significantly smaller in Casp3(-/-) mice whereas the Casp3(+/-) and Casp3(+/+) mice had normal hair cell numbers. CONCLUSIONS: These results indicate that caspase-3 is essential for correct functioning of the cochlea as well as normal development and function of the vestibule.
Asunto(s)
Caspasa 3/deficiencia , Oído Interno/enzimología , Oído Interno/fisiopatología , Enfermedades Vestibulares/enzimología , Enfermedades Vestibulares/fisiopatología , Animales , Conducta Animal/fisiología , Caspasa 3/genética , Modelos Animales de Enfermedad , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Fenotipo , Enfermedades Vestibulares/genética , Vestíbulo del Laberinto/enzimología , Vestíbulo del Laberinto/metabolismo , Vestíbulo del Laberinto/fisiopatologíaRESUMEN
The vestibular system of the inner ear is responsible for the perception of motion and gravity. Key elements of this organ are otoconia, tiny biomineral particles in the utricle and the saccule. In response to gravity or linear acceleration, otoconia deflect the stereocilia of the hair cells, thus transducing kinetic movements into sensorineural action potentials. Here, we present an allelic series of mutations at the otoconia-deficient head tilt (het) locus, affecting the gene for NADPH oxidase 3 (Nox3). This series of mutations identifies for the first time a protein with a clear enzymatic function as indispensable for otoconia morphogenesis.
Asunto(s)
Mutación , NADPH Oxidasas/genética , Enfermedades Vestibulares/genética , Vestíbulo del Laberinto/anomalías , Vestíbulo del Laberinto/enzimología , Animales , Mapeo Cromosómico , Genes Recesivos , Sensación de Gravedad , Ratones , Ratones Mutantes , Morfogénesis/genética , NADPH Oxidasas/fisiología , Propiocepción , Enfermedades Vestibulares/enzimología , Vestíbulo del Laberinto/anatomía & histologíaRESUMEN
This study was undertaken to examine the expression of inducible nitric oxide synthase (iNOS / NOS II) in the hydropic vestibule of guinea pigs. Animals were systemically sensitized with 500 microg of keyhole limpet hemocyanin. Two weeks after the first injection, keyhole limpet hemocyanin (100 microg/5 microl) was injected into the endolymphatic sac following the intradural approach, and the next day temporal bones were removed for the immunohistochemical examination. Endolymphatic hydrops was evidenced by the expansion of the Reissner's membrane in the cochlea after direct injection of keyhole limpet hemocyanin into the endolymphatic sac. Inducible nitric oxide synthase expression was increased in the sensory cells, supporting cells and vestibular ganglion cells, while temporal bones, where only phosphate buffered saline was injected, did not show any inducible nitric oxide synthase immunoreactivity. High levels of inducible nitric oxide synthase-catalyzed nitric oxide were detected prior to the development of the inner ear dysfunction. Our results suggest that the occurrence of inducible nitric oxide synthase immunoreactivity parallels the inner ear disturbance as seen in endolymphatic hydrops.