RESUMEN
We report the cases of two Spanish pediatric patients with hypotonia, muscle weakness and feeding difficulties at birth. Whole-exome sequencing (WES) uncovered two new homozygous VAMP1 (Vesicle Associated Membrane Protein 1) splicing variants, NM_014231.5:c.129+5 G > A in the boy patient (P1) and c.341-24_341-16delinsAGAAAA in the girl patient (P2). This gene encodes the vesicle-associated membrane protein 1 (VAMP1) that is a component of a protein complex involved in the fusion of synaptic vesicles with the presynaptic membrane. VAMP1 has a highly variable C-terminus generated by alternative splicing that gives rise to three main isoforms (A, B and D), being VAMP1A the only isoform expressed in the nervous system. In order to assess the pathogenicity of these variants, expression experiments of RNA for VAMP1 were carried out. The c.129+5 G > A and c.341-24_341-16delinsAGAAAA variants induced aberrant splicing events resulting in the deletion of exon 2 (r.5_131del; p.Ser2TrpfsTer7) in the three isoforms in the first case, and the retention of the last 14 nucleotides of the 3' of intron 4 (r.340_341ins341-14_341-1; p.Ile114AsnfsTer77) in the VAMP1A isoform in the second case. Pathogenic VAMP1 variants have been associated with autosomal dominant spastic ataxia 1 (SPAX1) and with autosomal recessive presynaptic congenital myasthenic syndrome (CMS). Our patients share the clinical manifestations of CMS patients with two important differences: they do not show the typical electrophysiological pattern that suggests pathology of pre-synaptic neuromuscular junction, and their muscular biopsies present hypertrophic fibers type 1. In conclusion, our data expand both genetic and phenotypic spectrum associated with VAMP1 variants.
Asunto(s)
Homocigoto , Síndromes Miasténicos Congénitos , Fenotipo , Proteína 1 de Membrana Asociada a Vesículas , Femenino , Humanos , Masculino , Empalme Alternativo/genética , Secuenciación del Exoma , Mutación , Síndromes Miasténicos Congénitos/genética , Síndromes Miasténicos Congénitos/patología , Isoformas de Proteínas/genética , Empalme del ARN/genética , Proteína 1 de Membrana Asociada a Vesículas/genética , Lactante , PreescolarRESUMEN
We report a 9-year-old Spanish boy with severe psychomotor developmental delay, short stature, microcephaly and abnormalities of the brain morphology, including cerebellar atrophy. Whole-exome sequencing (WES) uncovered two novel de novo variants, a hemizygous variant in CASK (Calcium/Calmodulin Dependent Serine Protein Kinase) and a heterozygous variant in EEF2 (Eukaryotic Translation Elongation Factor 2). CASK gene encodes the peripheral plasma membrane protein CASK that is a scaffold protein located at the synapses in the brain. The c.2506-6 A > G CASK variant induced two alternative splicing events that account for the 80% of the total transcripts, which are likely to be degraded by NMD. Pathogenic variants in CASK have been associated with severe neurological disorders such as mental retardation with or without nystagmus also called FG syndrome 4 (FGS4), and intellectual developmental disorder with microcephaly and pontine and cerebellar hypoplasia (MICPCH). Heterozygous variants in EEF2, which encodes the elongation factor 2 (eEF2), have been associated to Spinocerebellar ataxia 26 (SCA26) and more recently to a childhood-onset neurodevelopmental disorder with benign external hydrocephalus. The yeast model system used to investigate the functional consequences of the c.34 A > G EEF2 variant supported its pathogenicity by demonstrating it affects translational fidelity. In conclusion, the phenotype associated with the CASK variant is more severe and masks the milder phenotype of EEF2 variant.
Asunto(s)
Discapacidad Intelectual , Microcefalia , Humanos , Microcefalia/genética , Mutación , Factor 2 de Elongación Peptídica/genética , Fenotipo , Discapacidad Intelectual/genéticaRESUMEN
We report the clinical and genetic features of a Caucasian girl who presented a severe neurodevelopmental disorder with drug-resistant epilepsy, hypotonia, severe gastro-esophageal reflux and brain magnetic resonance imaging anomalies. WES uncovered a novel variant in homozygosis (g.197092814_197092824delinsC) in HECW2 gene that encodes the E3 ubiquitin-protein ligase HECW2. This protein induces ubiquitination and is implicated in the regulation of several important pathways involved in neurodevelopment and neurogenesis. Furthermore, de novo heterozygous missense variants in this gene have been associated with neurodevelopmental disorder with hypotonia, seizures, and absent language (NDHSAL). The homozygous variant of our patient disrupts the splice donor site of intron 22 and causes the elimination of exon 22 (r.3766_3917+1del) leading to an in-frame deletion of the protein (p.Leu1256_Trp1306del). Functional studies showed a twofold increase of its RNA expression, while the protein expression level was reduced by 60%, suggesting a partial loss-of-function mechanism of pathogenesis. Thus, this is the first patient with NDHSAL caused by an autosomal recessive splicing variant in HECW2.
Asunto(s)
Encefalopatías , Trastornos del Neurodesarrollo , Ubiquitina-Proteína Ligasas , Femenino , Humanos , Hipotonía Muscular/genética , Trastornos del Neurodesarrollo/genética , Empalme del ARN , Convulsiones , Ubiquitina-Proteína Ligasas/genética , UbiquitinaciónRESUMEN
VAMP2 encodes the vesicular SNARE protein VAMP2 (also called synaptobrevin-2). Together with its partners syntaxin-1A and synaptosomal-associated protein 25 (SNAP25), VAMP2 mediates fusion of synaptic vesicles to release neurotransmitters. VAMP2 is essential for vesicular exocytosis and activity-dependent neurotransmitter release. Here, we report five heterozygous de novo mutations in VAMP2 in unrelated individuals presenting with a neurodevelopmental disorder characterized by axial hypotonia (which had been present since birth), intellectual disability, and autistic features. In total, we identified two single-amino-acid deletions and three non-synonymous variants affecting conserved residues within the C terminus of the VAMP2 SNARE motif. Affected individuals carrying de novo non-synonymous variants involving the C-terminal region presented a more severe phenotype with additional neurological features, including central visual impairment, hyperkinetic movement disorder, and epilepsy or electroencephalography abnormalities. Reconstituted fusion involving a lipid-mixing assay indicated impairment in vesicle fusion as one of the possible associated disease mechanisms. The genetic synaptopathy caused by VAMP2 de novo mutations highlights the key roles of this gene in human brain development and function.
Asunto(s)
Discapacidad Intelectual/genética , Hipotonía Muscular/genética , Trastornos del Neurodesarrollo/genética , Neuronas/metabolismo , Sinapsis/metabolismo , Proteína 2 de Membrana Asociada a Vesículas/genética , Adolescente , Trastorno Autístico/genética , Trastorno Autístico/metabolismo , Encéfalo/diagnóstico por imagen , Niño , Preescolar , Epilepsia/metabolismo , Exocitosis , Femenino , Heterocigoto , Humanos , Lípidos/química , Imagen por Resonancia Magnética , Masculino , Fusión de Membrana , Trastornos del Movimiento/genética , Mutación , Trastornos del Neurodesarrollo/metabolismo , Neurotransmisores/metabolismo , Fenotipo , Dominios Proteicos , Proteínas R-SNARE/metabolismo , Proteína 2 de Membrana Asociada a Vesículas/fisiologíaRESUMEN
Striated muscle needs to maintain cellular homeostasis in adaptation to increases in physiological and metabolic demands. Failure to do so can result in rhabdomyolysis. The identification of novel genetic conditions associated with rhabdomyolysis helps to shed light on hitherto unrecognized homeostatic mechanisms. Here we report seven individuals in six families from different ethnic backgrounds with biallelic variants in MLIP, which encodes the muscular lamin A/C-interacting protein, MLIP. Patients presented with a consistent phenotype characterized by mild muscle weakness, exercise-induced muscle pain, variable susceptibility to episodes of rhabdomyolysis, and persistent basal elevated serum creatine kinase levels. The biallelic truncating variants were predicted to result in disruption of the nuclear localizing signal of MLIP. Additionally, reduced overall RNA expression levels of the predominant MLIP isoform were observed in patients' skeletal muscle. Collectively, our data increase the understanding of the genetic landscape of rhabdomyolysis to now include MLIP as a novel disease gene in humans and solidifies MLIP's role in normal and diseased skeletal muscle homeostasis.
Asunto(s)
Proteínas Co-Represoras/genética , Creatina Quinasa , Variación Genética/genética , Enfermedades Musculares/genética , Mialgia/genética , Proteínas Nucleares/genética , Rabdomiólisis/genética , Adolescente , Niño , Preescolar , Creatina Quinasa/sangre , Femenino , Humanos , Masculino , Enfermedades Musculares/sangre , Enfermedades Musculares/diagnóstico por imagen , Mialgia/sangre , Mialgia/diagnóstico por imagen , Rabdomiólisis/sangre , Rabdomiólisis/diagnóstico por imagen , Adulto JovenRESUMEN
We report the clinical, biochemical and genetic findings from a Spanish boy of Caucasian origin who presented with fever-dependent RALF (recurrent acute liver failure) and osteogenesis imperfecta (OI). Whole-exome sequencing (WES) uncovered two compound heterozygous variants in NBAS (c.[1265 T > C];[1549C > T]:p.[(Leu422Pro)];[(Arg517Cys)]), and a heterozygous variant in P4HB (c.[194A > G];[194=]:p.[(Lys65Arg)];[(Lys65=)]) that was transmitted from the clinically unaffected mother who was mosaic carrier of the variant. Variants in NBAS protein have been associated with ILFS2 (infantile liver failure syndrome-2), SOPH syndrome (short stature, optic nerve atrophy, and Pelger-Huët anomaly syndrome), and multisystem diseases. Several patients showed clinical manifestations affecting the skeletal system, such as osteoporosis, pathologic fractures and OI. Experiments in the patient's fibroblasts demonstrated that mutated NBAS protein is overexpressed and thermally unstable, and reduces the expression of MGP, a regulator of bone homeostasis. Variant in PDI (protein encoded by P4HB) has been associated with CLCRP1 (Cole-Carpenter syndrome-1), a type of severe OI. An increase of COL1A2 protein retention was observed in the patient's fibroblasts. In order to study if the variant in P4HB was involved in the alteration in collagen trafficking, overexpression experiments of PDI were carried out. These experiments showed that overexpression of mutated PDI protein produces an increase in COL1A2 retention. In conclusion, these results corroborate that the variants in NBAS are responsible for the liver phenotype, and demonstrate that the variant in P4HB is involved in the bone phenotype, probably in synergy with NBAS variants.
Asunto(s)
Colágeno Tipo I/genética , Fallo Hepático Agudo/genética , Proteínas de Neoplasias/genética , Osteogénesis Imperfecta/genética , Procolágeno-Prolina Dioxigenasa/genética , Proteína Disulfuro Isomerasas/genética , Niño , Preescolar , Craneosinostosis/complicaciones , Craneosinostosis/genética , Craneosinostosis/patología , Enanismo/diagnóstico por imagen , Enanismo/genética , Enanismo/patología , Anomalías del Ojo/complicaciones , Anomalías del Ojo/genética , Anomalías del Ojo/patología , Fiebre/complicaciones , Fiebre/genética , Heterocigoto , Humanos , Hidrocefalia/complicaciones , Hidrocefalia/genética , Hidrocefalia/patología , Lactante , Recién Nacido , Hígado/diagnóstico por imagen , Hígado/patología , Fallo Hepático Agudo/complicaciones , Fallo Hepático Agudo/diagnóstico por imagen , Fallo Hepático Agudo/patología , Masculino , Mutación/genética , Osteogénesis Imperfecta/complicaciones , Osteogénesis Imperfecta/diagnóstico por imagen , Osteogénesis Imperfecta/patología , Fenotipo , Secuenciación del ExomaRESUMEN
Dilated cardiomyopathy (DCM) belongs to the most frequent forms of cardiomyopathy mainly characterized by cardiac dilatation and reduced systolic function. Although most cases of DCM are classified as sporadic, 20-30% of cases show a heritable pattern. Familial forms of DCM are genetically heterogeneous, and mutations in several genes have been identified that most commonly play a role in cytoskeleton and sarcomere-associated processes. Still, a large number of familial cases remain unsolved. Here, we report five individuals from three independent families who presented with severe dilated cardiomyopathy during the neonatal period. Using whole-exome sequencing (WES), we identified causative, compound heterozygous missense variants in RPL3L (ribosomal protein L3-like) in all the affected individuals. The identified variants co-segregated with the disease in each of the three families and were absent or very rare in the human population, in line with an autosomal recessive inheritance pattern. They are located within the conserved RPL3 domain of the protein and were classified as deleterious by several in silico prediction software applications. RPL3L is one of the four non-canonical riboprotein genes and it encodes the 60S ribosomal protein L3-like protein that is highly expressed only in cardiac and skeletal muscle. Three-dimensional homology modeling and in silico analysis of the affected residues in RPL3L indicate that the identified changes specifically alter the interaction of RPL3L with the RNA components of the 60S ribosomal subunit and thus destabilize its binding to the 60S subunit. In conclusion, we report that bi-allelic pathogenic variants in RPL3L are causative of an early-onset, severe neonatal form of dilated cardiomyopathy, and we show for the first time that cytoplasmic ribosomal proteins are involved in the pathogenesis of non-syndromic cardiomyopathies.
Asunto(s)
Cardiomiopatía Dilatada/genética , Mutación Missense/genética , Proteínas Ribosómicas/genética , Ribosomas/genética , Alelos , Exoma/genética , Femenino , Corazón/fisiopatología , Humanos , Lactante , Recién Nacido , Masculino , Músculo Esquelético/fisiopatología , Linaje , Fenotipo , ARN/genética , Proteína Ribosomal L3RESUMEN
We report the case of a Caucasian Spanish origin female who showed severe psychomotor developmental delay, hypotonia, strabismus, epilepsy, short stature, and poor verbal language development. Brain magnetic resonance imaging scans showed thickened corpus callosum, cortical malformations, and dilated and abnormal configuration of the lateral ventricles without hydrocephalus. Whole-exome sequence uncovered a de novo variant in the microtubule associated serine/threonine kinase 1 gene (MAST1; NM_014975.3:c.1565G>A:p.(Gly522Glu)) that encodes for the MAST1. Only 12 patients have been identified worldwide with 10 different variants in this gene: six patients with mega-corpus-callosum syndrome with cerebellar hypoplasia and cortical malformations; two patients with microcephaly and cerebellar hypoplasia; two patients with autism, one patient with diplegia, and one patient with microcephaly and dysmorphism. Our patient shows a new phenotypic subtype defined by mega-corpus-callosum syndrome with cortical malformations without cerebellar hypoplasia. In conclusion, our data expand the phenotypic spectrum associated to MAST1 gene variants.
Asunto(s)
Agenesia del Cuerpo Calloso/genética , Cerebelo/anomalías , Microcefalia/genética , Proteínas Asociadas a Microtúbulos/genética , Malformaciones del Sistema Nervioso/genética , Proteínas Serina-Treonina Quinasas/genética , Agenesia del Cuerpo Calloso/complicaciones , Agenesia del Cuerpo Calloso/patología , Cerebelo/patología , Niño , Discapacidades del Desarrollo/complicaciones , Discapacidades del Desarrollo/genética , Discapacidades del Desarrollo/patología , Enanismo/complicaciones , Enanismo/genética , Enanismo/patología , Femenino , Humanos , Hidrocefalia/complicaciones , Hidrocefalia/genética , Hidrocefalia/patología , Lactante , Masculino , Malformaciones del Desarrollo Cortical/genética , Malformaciones del Desarrollo Cortical/patología , Microcefalia/complicaciones , Microcefalia/patología , Hipotonía Muscular/complicaciones , Hipotonía Muscular/genética , Hipotonía Muscular/patología , Malformaciones del Sistema Nervioso/complicaciones , Malformaciones del Sistema Nervioso/patología , Secuenciación del ExomaRESUMEN
We report the clinical and biochemical findings from a patient who presented with Bosch-Boonstra-Schaaf optic atrophy syndrome (BBSOAS), an autosomal-dominant disorder characterized by optic atrophy, developmental delay and intellectual disability. In addition, the patient also displays hypotonia, stroke-like episodes, and complex IV deficiency of the mitochondrial respiratory chain. Whole-exome sequencing (WES) uncovered a novel heterozygous mutation in the NR2F1 gene (NM_005654:c.286A>G:p.Lys96Glu) that encodes for the COUP transcription factor 1 protein (COUP-TF1). Loss-of-function mutations in this protein have been associated with BBSOAS, and a luciferase reporter assay showed that this variant, in the zinc-finger DNA-binding domain (DBD) of COUP-TF1 protein, impairs its transcriptional activity. The additional features of this patient are more related with mitochondrial diseases that with BBSOAS, indicating a mitochondrial involvement. Finally, our data expand both the genetic and phenotypic spectrum associated with NR2F1 gene mutations.
Asunto(s)
Factor de Transcripción COUP I/genética , Mitocondrias/genética , Mutación , Atrofia Óptica/diagnóstico , Atrofia Óptica/genética , Alelos , Secuencia de Aminoácidos , Sustitución de Aminoácidos , Biomarcadores , Respiración de la Célula , Electroencefalografía , Femenino , Estudios de Asociación Genética , Genotipo , Humanos , Imagen por Resonancia Magnética , Mitocondrias/metabolismo , Linaje , Fenotipo , Síndrome , Secuenciación del ExomaRESUMEN
We report the clinical and genetic findings in a 15-year-old Spanish boy presenting prenatal and postnatal growth retardation, reduced subcutaneous adipose tissue, premature skin wrinkling, sparse hair, short distal phalanges with small nails, umbilical hernia, wide anterior fontanel, and normal cognitive and motor development. Exome sequencing uncovered a heterozygous mutation in SLC25A24 (NM_013386: c.650G>A: p.R217H) that encodes for the calcium-binding mitochondrial carrier protein SCaMC-1. This gain-of-function variant has been previously associated with Fontaine syndrome and Gorlin-Chaudhry-Moss syndrome, two entities that show overlapping features, and have been recently subsumed under the name Fontaine progeroid syndrome (FPS; MIM: 612289) in OMIM. Here, we describe the first male patient with genetically confirmed FPS who survives at least until adolescence.
Asunto(s)
Antiportadores/genética , Proteínas de Unión al Calcio/genética , Proteínas Mitocondriales/genética , Mutación/genética , Progeria/genética , Anomalías Múltiples/genética , Adolescente , Secuencia de Aminoácidos , Antiportadores/química , Secuencia de Bases , Proteínas de Unión al Calcio/química , Niño , Preescolar , Anomalías Craneofaciales/genética , Conducto Arterioso Permeable/genética , Femenino , Trastornos del Crecimiento , Humanos , Hipertricosis/genética , Lactante , Recién Nacido , Masculino , Proteínas Mitocondriales/química , Progeria/diagnóstico por imagen , SíndromeRESUMEN
We have developed a new functional complementation approach to clone modifier genes which overexpression is able to suppress the biochemical defects caused by mtDNA mutations (suppressor genes). This strategy consists in transferring human genes into respiratory chain-deficient fibroblasts, followed by a metabolic selection in a highly selective medium. We used a normalized expression cDNA library in an episomal vector (pREP4) to transfect the fibroblasts, and a medium with glutamine and devoid of any carbohydrate source to select metabolically. Growing the patient's fibroblasts in this selective medium, the deficient cells rapidly disappear unless they are rescued by the cDNA of a suppressor gene. The use of an episomal vector allows us to carry out several rounds of transfection/selection (cyclical phenotypic rescue) to enrich the rescue with true clones of suppressor genes. Using fibroblasts from a patient with epileptic encephalopathy with the m.3946G>A (p.E214K) mutation in the MT-ND1 gene, several candidate genes were identified and one of them was characterized functionally. Thus, overexpression of MRPS18C gene (that encode for bS18m protein) suppressed the molecular defects produced by this mtDNA mutation, recovering the complex I activity and reducing the ROS produced by this complex to normal levels. We suggest that modulation of bS18m expression may be an effective therapeutic strategy for the patients with this mutation.
Asunto(s)
ADN Mitocondrial/genética , Genes Modificadores , Genes Supresores , Proteínas Mitocondriales/genética , Proteínas Ribosómicas/genética , Células Cultivadas , Fibroblastos/citología , Fibroblastos/metabolismo , Regulación de la Expresión Génica , Biblioteca de Genes , Humanos , Mutación , NADH Deshidrogenasa/genética , ARN Largo no Codificante/genética , ARN Largo no Codificante/metabolismo , Especies Reactivas de Oxígeno/metabolismo , Análisis de Secuencia de ADN , TransfecciónRESUMEN
We report the clinical and genetic findings in a Spanish boy who presented MEGDEL syndrome, a very rare inborn error of metabolism. Whole-exome sequencing uncovered a new homozygous mutation in the serine active site containing 1 (SERAC1) gene, which is essential for both mitochondrial function and intracellular cholesterol trafficking. Functional studies in patient fibroblasts showed that p.D224G mutation affects the intracellular cholesterol trafficking. Only three missense mutations in this gene have been described before, being p.D224G the first missense mutation outside of the SERAC1 serine-lipase domain. Therefore, we conclude that the defect in cholesterol trafficking is not limited to alterations in this specific part of the protein.
Asunto(s)
Hidrolasas de Éster Carboxílico/genética , Colesterol/metabolismo , Errores Innatos del Metabolismo Lipídico/genética , Mutación Missense , Transporte Biológico/genética , Encefalopatías Metabólicas Innatas/genética , Encefalopatías Metabólicas Innatas/metabolismo , Hidrolasas de Éster Carboxílico/química , Dominio Catalítico/genética , Niño , Consanguinidad , Humanos , Espacio Intracelular/metabolismo , Lipasa/química , Errores Innatos del Metabolismo Lipídico/metabolismo , Masculino , Enfermedades Neurodegenerativas/genética , Enfermedades Neurodegenerativas/metabolismo , Estructura Terciaria de Proteína/genéticaRESUMEN
We report the clinical and biochemical findings from two unrelated patients who presented with a novel syndrome: encephalopathy, intellectual disability, severe hypotonia, chorea and optic atrophy. Whole exome sequencing (WES) uncovered a homozygous mutation in the ATP8A2 gene (NM_016529:c.1287G > T, p.K429N) in one patient and compound heterozygous mutations (c.1630G > C, p.A544P and c.1873C > T, p.R625W) in the other. Only one haploinsufficiency case and a family with a homozygous mutation in ATP8A2 gene (c.1128C > G, p.I376M) have been described so far, with phenotypes that differed slightly from the patients described herein. In conclusion, our data expand both the genetic and phenotypic spectrum associated with ATP8A2 gene mutations.
Asunto(s)
Adenosina Trifosfatasas/genética , Encefalopatías/genética , Corea/genética , Discapacidad Intelectual/genética , Hipotonía Muscular/genética , Mutación , Atrofia Óptica/genética , Proteínas de Transferencia de Fosfolípidos/genética , Encefalopatías/complicaciones , Niño , Preescolar , Corea/complicaciones , Femenino , Homocigoto , Humanos , Discapacidad Intelectual/complicaciones , Hipotonía Muscular/complicaciones , Atrofia Óptica/complicaciones , Linaje , Síndrome , Secuenciación del ExomaRESUMEN
We report the case of a Spanish pediatric patient with developmental delay, hypotonia, feeding difficulties, visual problems, and hyperkinetic movements. Whole-exome sequencing uncovered a new heterozygous de novo Synaptotagmin 1 (SYT1) missense variant, NM_005639.3:c.930T>A (p.Asp310Glu), in a female proband. This gene encodes the synaptotagmin-1 (SYT1) protein, which is a component of a protein complex involved in the fusion of synaptic vesicles with the presynaptic membrane. Pathogenic SYT1 variants have been associated with Baker-Gordon syndrome (BAGOS), an autosomal dominant neurodevelopmental disorder. Although up to 30 cases have been identified worldwide, to the best of our knowledge, this is the first patient described with mitochondrial respiratory chain deficiencies and rod-cone dysfunction. In conclusion, our data expand both the genetic and phenotypic spectrum associated with SYT1 variants.
Asunto(s)
Fenotipo , Sinaptotagmina I , Humanos , Femenino , Sinaptotagmina I/genética , Mutación Missense , Secuenciación del Exoma , Niño , Preescolar , Discapacidades del Desarrollo/genética , Discapacidades del Desarrollo/patologíaRESUMEN
Genetic defects affecting steroid biosynthesis cause cortisol deficiency and differences of sex development; among these defects are recessive mutations in the steroidogenic enzymes CYP11A1 and CYP11B, whose function is supported by reducing equivalents donated by ferredoxin reductase (FDXR) and ferredoxin. So far, mutations in the mitochondrial flavoprotein FDXR have been associated with a progressive neuropathic mitochondriopathy named FDXR-related mitochondriopathy (FRM), but cortisol insufficiency has not been documented. However, patients with FRM often experience worsening or demise following stress associated with infections. We investigated 2 female patients with FRM carrying the potentially novel homozygous FDXR mutation p.G437R with ambiguous genitalia at birth and sudden death in the first year of life; they presented with cortisol deficiency and androgen excess compatible with 11-hydroxylase deficiency. In addition, steroidogenic FDXR-variant cell lines reprogrammed from 3 patients with FRM fibroblasts displayed deficient mineralocorticoid and glucocorticoid production. Finally, Fdxr-mutant mice allelic to the severe p.R386W human variant showed reduced progesterone and corticosterone production. Therefore, our comprehensive studies show that human FDXR variants may cause compensated but possibly life-threatening adrenocortical insufficiency in stress by affecting adrenal glucocorticoid and mineralocorticoid synthesis through direct enzyme inhibition, most likely in combination with disturbed mitochondrial redox balance.
Asunto(s)
Insuficiencia Suprarrenal , Ferredoxina-NADP Reductasa , Humanos , Femenino , Insuficiencia Suprarrenal/genética , Insuficiencia Suprarrenal/metabolismo , Animales , Ratones , Ferredoxina-NADP Reductasa/genética , Ferredoxina-NADP Reductasa/metabolismo , Mutación , Hidrocortisona/metabolismo , Lactante , Enfermedades Mitocondriales/genética , Enfermedades Mitocondriales/metabolismo , Masculino , Fibroblastos/metabolismo , Trastornos del Desarrollo Sexual/genética , Trastornos del Desarrollo Sexual/metabolismo , Trastornos del Desarrollo Sexual/patologíaRESUMEN
We describe a West syndrome (WS) patient with unidentified etiology that evolved to Lennox-Gastaut syndrome. The mitochondrial respiratory chain of the patient showed a simple complex I deficiency in fibroblasts. Whole-exome sequencing (WES) uncovered two heterozygous mutations in NDUFV2 gene that were reassigned to a pseudogene. With the WES data, it was possible to obtain whole mitochondrial DNA sequencing and to identify a heteroplasmic variant in the MT-ND1 (MTND1) gene (m.3946G>A, p.E214K). The expression of the gene in patient fibroblasts was not affected but the protein level was significantly reduced, suggesting that protein stability was affected by this mutation. The lower protein level also affected assembly of complex I and supercomplexes (I/III2 /IV and I/III2 ), leading to complex I deficiency. While ATP levels at steady state under stress conditions were not affected, the amount of ROS produced by complex I was significantly increased.
Asunto(s)
Exoma , Secuenciación de Nucleótidos de Alto Rendimiento , Discapacidad Intelectual/genética , Mutación , NADH Deshidrogenasa/genética , Espasmos Infantiles/genética , Secuencia de Aminoácidos , Análisis Mutacional de ADN , Femenino , Estudios de Asociación Genética , Humanos , Lactante , Discapacidad Intelectual/metabolismo , Síndrome de Lennox-Gastaut , Datos de Secuencia Molecular , NADH Deshidrogenasa/química , NADH Deshidrogenasa/metabolismo , Alineación de Secuencia , Espasmos Infantiles/metabolismoRESUMEN
We show the physiological effects and molecular characterization of overexpression of the catalytic core of mitochondrial DNA (mtDNA) polymerase (pol γ-α) in muscle of Drosophila melanogaster. Muscle-specific overexpression of pol γ-α using the UAS/GAL4 (where UAS is upstream activation sequence) system produced more than 90% of lethality at the end of pupal stage at 25°C, and the survivor adult flies showed a significant reduction in life span. The survivor flies displayed a decreased mtDNA level that is accompanied by a corresponding decrease in the levels of the nucleoid-binding protein mitochondrial transcription factor A (mtTFA). Furthermore, an increase in apoptosis is detected in larvae and adults overexpressing pol γ-α. We suggest that the pupal lethality and reduced life span of survivor adult flies are both caused mainly by massive apoptosis of muscle cells induced by mtDNA depletion.
Asunto(s)
Apoptosis/genética , ADN Mitocondrial/metabolismo , ADN Polimerasa Dirigida por ADN/genética , ADN Polimerasa Dirigida por ADN/metabolismo , Drosophila melanogaster/enzimología , Regulación de la Expresión Génica/fisiología , Músculos/metabolismo , Animales , Animales Modificados Genéticamente , Apoptosis/fisiología , Southern Blotting , Dominio Catalítico/genética , ADN Polimerasa gamma , Proteínas de Drosophila/metabolismo , Discos Imaginales/citología , Immunoblotting , Pupa/enzimología , Análisis de Supervivencia , Factores de Transcripción/metabolismoRESUMEN
BACKGROUND: HUPRA syndrome is a rare mitochondrial disease characterized by hyperuricemia, pulmonary hypertension, renal failure in infancy and alkalosis. This syndrome was previously described in three patients with a homozygous mutation c.1169A > G (p.D390G) in SARS2, encoding the mitochondrial seryl-tRNA synthetase. CASE PRESENTATION: Here we report the clinical and genetic findings in a girl and her brother. Both patients were clinically diagnosed with the HUPRA syndrome. Analysis of the pedigree identified a new homozygous mutation c.1205G > A (p.R402H) in SARS2 gene. This mutation is very rare in the population and it is located at the C-terminal globular domain of the homodimeric enzyme very close to p.D390G. CONCLUSION: Several data support that p.R402H mutation in SARS2 is a new cause of HUPRA syndrome.
Asunto(s)
Alcalosis Respiratoria/genética , Hipertensión Pulmonar/genética , Hiperuricemia/genética , Proteínas Mitocondriales/genética , Polimorfismo de Nucleótido Simple/genética , Insuficiencia Renal/genética , Serina-ARNt Ligasa/genética , Femenino , Marcadores Genéticos/genética , Humanos , Lactante , Mutación/genética , SíndromeRESUMEN
We report the case of a 16-year-old Spanish boy with cerebellar and spinal muscular atrophy, spasticity, psychomotor retardation, nystagmus, ophthalmoparesis, epilepsy, and mitochondrial respiratory chain (MRC) deficiency. Whole exome sequencing (WES) uncovered three variants (two of them novel) in a compound heterozygous in EXOSC8 gene (NM_181503.3:c.[390+1delG];[628C>T;815G>C]) that encodes the exosome complex component RRP43 protein (EXOSC8). In order to assess the pathogenicity of these variants, expression experiments of RNA and protein for EXOSC8 were carried out. The c.[390+1delG] variant produces the elimination of exon 7 (r.[345_390del]; p.[Ser116LysfsTer27]) and a decrease of the RNA expression in relation to the other allele (p.[Pro210Ser;Ser272Thr]). Furthermore, total mRNA expression is reduced by 30% and the protein level by 65%. EXOSC8 is an essential protein of the exosome core, a ubiquitously expressed complex responsible for RNA processing and degradation. Recessive mutations in EXOSC8 cause pontocerebellar hypoplasia type 1C (PCH1C), and currently, only two homozygous variants in this gene have been described. However, unlike PCH1C-affected individuals with EXOSC8 variants, our patient presents a normal supratentorial cerebral tissue (neither corpus callosum hypoplasia nor hypomyelination) with a less severe phenotype and longer survival. In conclusion, our data expand both genetic and phenotypic spectrum associated with EXOSC8 variants.