RESUMEN
Reelin (RELN) is a secreted glycoprotein essential for cerebral cortex development. In humans, recessive RELN variants cause cortical and cerebellar malformations, while heterozygous variants were associated with epilepsy, autism, and mild cortical abnormalities. However, the functional effects of RELN variants remain unknown. We identified inherited and de novo RELN missense variants in heterozygous patients with neuronal migration disorders (NMDs) as diverse as pachygyria and polymicrogyria. We investigated in culture and in the developing mouse cerebral cortex how different variants impacted RELN function. Polymicrogyria-associated variants behaved as gain-of-function, showing an enhanced ability to induce neuronal aggregation, while those linked to pachygyria behaved as loss-of-function, leading to defective neuronal aggregation/migration. The pachygyria-associated de novo heterozygous RELN variants acted as dominant-negative by preventing WT RELN secretion in culture, animal models, and patients, thereby causing dominant NMDs. We demonstrated how mutant RELN proteins in vitro and in vivo predict cortical malformation phenotypes, providing valuable insights into the pathogenesis of such disorders.
Asunto(s)
Moléculas de Adhesión Celular Neuronal , Movimiento Celular , Proteínas de la Matriz Extracelular , Mutación Missense , Proteínas del Tejido Nervioso , Proteína Reelina , Serina Endopeptidasas , Humanos , Animales , Proteínas de la Matriz Extracelular/genética , Proteínas de la Matriz Extracelular/metabolismo , Serina Endopeptidasas/genética , Serina Endopeptidasas/metabolismo , Moléculas de Adhesión Celular Neuronal/genética , Moléculas de Adhesión Celular Neuronal/metabolismo , Proteínas del Tejido Nervioso/genética , Proteínas del Tejido Nervioso/metabolismo , Ratones , Femenino , Masculino , Movimiento Celular/genética , Neuronas/metabolismo , Neuronas/patología , Polimicrogiria/genética , Polimicrogiria/patología , Corteza Cerebral/metabolismo , Corteza Cerebral/patología , Heterocigoto , Lisencefalia/genética , Lisencefalia/patología , AlelosRESUMEN
Cajal-Retzius cells (CRs) are key players in cerebral cortex development, and they display a unique transcriptomic identity. Here, we use scRNA-seq to reconstruct the differentiation trajectory of mouse hem-derived CRs, and we unravel the transient expression of a complete gene module previously known to control multiciliogenesis. However, CRs do not undergo centriole amplification or multiciliation. Upon deletion of Gmnc, the master regulator of multiciliogenesis, CRs are initially produced but fail to reach their normal identity resulting in their massive apoptosis. We further dissect the contribution of multiciliation effector genes and identify Trp73 as a key determinant. Finally, we use in utero electroporation to demonstrate that the intrinsic competence of hem progenitors as well as the heterochronic expression of Gmnc prevent centriole amplification in the CR lineage. Our work exemplifies how the co-option of a complete gene module, repurposed to control a distinct process, may contribute to the emergence of novel cell identities.
Asunto(s)
Corteza Cerebral , Redes Reguladoras de Genes , Ratones , Animales , Corteza Cerebral/metabolismo , Neuronas/metabolismo , Diferenciación Celular/fisiología , Neurogénesis/genéticaRESUMEN
In the developing cerebral cortex, how progenitors that seemingly display limited diversity end up producing a vast array of neurons remains a puzzling question. The prevailing model suggests that temporal maturation of progenitors is a key driver in the diversification of the neuronal output. However, temporal constraints are unlikely to account for all diversity, especially in the ventral and lateral pallium where neuronal types significantly differ from their dorsal neocortical counterparts born at the same time. In this study, we implemented single-cell RNAseq to sample the diversity of progenitors and neurons along the dorso-ventral axis of the early developing pallium. We first identified neuronal types, mapped them on the tissue and determined their origin through genetic tracing. We characterised progenitor diversity and disentangled the gene modules underlying temporal versus spatial regulations of neuronal specification. Finally, we reconstructed the developmental trajectories followed by ventral and dorsal pallial neurons to identify lineage-specific gene waves. Our data suggest a model by which discrete neuronal fate acquisition from a continuous gradient of progenitors results from the superimposition of spatial information and temporal maturation.
Asunto(s)
Corteza Cerebral/metabolismo , Neuronas/metabolismo , Transcriptoma , Animales , Diferenciación Celular/fisiología , Corteza Cerebral/patología , Embrión de Mamíferos , Femenino , Factores de Transcripción Forkhead , Regulación del Desarrollo de la Expresión Génica , Proteínas de Homeodominio/metabolismo , Ratones , Ratones Endogámicos C57BL , Proteínas del Tejido Nervioso , Neurogénesis/fisiología , Proteínas Proto-Oncogénicas/metabolismoRESUMEN
BACKGROUND: Despite undisputable benefits, midtrimester prenatal surgery is not a cure for myelomeningocele (MMC): residual intracranial and motor deficits leading to lifelong handicap question the timing of prenatal surgery. Indeed, the timing and intensity of intrauterine spinal cord injury remains ill defined. OBJECTIVE: We aimed to describe the natural history of neuronal loss in MMC in utero based on postmortem pathology. STUDY DESIGN: Pathology findings were analyzed in 186 cases of myelomeningocele with lesion level between S1 and T1. Using a case-control, cross-sectional design, we investigated the timewise progression and topographic extension of neuronal loss between 13 and 39 weeks. Motor neurons were counted on histology at several spinal levels in 54 isolated MMC meeting quality criteria for cell counting. These were expressed as observed-to-expected ratios, after matching for gestational age and spinal level with 41 controls. RESULTS: Chiari II malformation increased from 30.7% to 91.6% after 16 weeks. The exposed spinal cord displayed early, severe, and progressive neuronal loss: the observed-to-expected count dropped from 17% to ≤2% after 16 weeks. Neuronal loss extended beyond the lesion to the upper levels: in cases <16 weeks, the observed-to-expected motor neuron count was 60% in the adjacent spinal cord, decreasing at a rate of 16% per week. Progressive loss was also found in the upper thoracic cord, but in much smaller proportions. The observed-over-expected ratio of motor neurons was not correlated with the level of myelomeningocele. CONCLUSIONS: Significant neuronal loss is present ≤16 weeks in the exposed cord and progressively extends cranially. Earlier prenatal repair (<16 weeks) could prevent Chiari II malformation in 69.3% of cases, rescue the 17% remaining motor neurons in the exposed cord, and prevent the extension to the upper spinal cord.
Asunto(s)
Malformación de Arnold-Chiari/patología , Edad Gestacional , Meningomielocele/patología , Neuronas Motoras/patología , Médula Espinal/patología , Aborto Inducido , Malformación de Arnold-Chiari/embriología , Autopsia , Progresión de la Enfermedad , Femenino , Terapias Fetales , Humanos , Vértebras Lumbares , Meningomielocele/embriología , Meningomielocele/cirugía , Procedimientos Neuroquirúrgicos , Embarazo , Primer Trimestre del Embarazo , Segundo Trimestre del Embarazo , Estudios Retrospectivos , Sacro , Vértebras TorácicasRESUMEN
Astrocytes are involved in several aspects of neuronal development and properties which are altered in intellectual disability (ID). Oligophrenin-1 is a RhoGAP protein implicated in actin cytoskeleton regulation, and whose mutations are associated with X-linked ID. Oligophrenin-1 is expressed in neurons, where its functions have been widely reported at the synapse, as well as in glial cells. However, its roles in astrocytes are still largely unexplored. Using in vitro and in vivo models of oligophrenin1 disruption in astrocytes, we found that oligophrenin1 regulates at the molecular level the RhoA/ROCK/MLC2 pathway in astroglial cells. We also showed at the cellular level that oligophrenin1 modulates astrocyte morphology and migration both in vitro and in vivo, and is involved in glial scar formation. Altogether, these data suggest that oligophrenin1 deficiency alters not only neuronal but also astrocytic functions, which might contribute to the development of ID.
Asunto(s)
Astrocitos , Discapacidad Intelectual , Proteínas del Citoesqueleto/genética , Humanos , Discapacidad Intelectual/genética , Neuroglía , NeuronasRESUMEN
Changes in transcriptional regulation through cis-regulatory elements are thought to drive brain evolution. However, how this impacts the identity of primate cortical neurons is still unresolved. Here, we show that primate-specific cis-regulatory sequences upstream of the Dbx1 gene promote human-like expression in the mouse embryonic cerebral cortex, and this imparts cell identity. Indeed, while Dbx1 is expressed in highly restricted cortical progenitors in the mouse ventral pallium, it is maintained in neurons in primates. Phenocopy of the primate-like Dbx1 expression in mouse cortical progenitors induces ectopic Cajal-Retzius and subplate (SP) neurons, which are transient populations playing crucial roles in cortical development. A conditional expression solely in neurons uncouples mitotic and postmitotic activities of Dbx1 and exclusively promotes a SP-like fate. Our results highlight how transcriptional changes of a single fate determinant in postmitotic cells may contribute to the expansion of neuronal diversity during cortical evolution.
Asunto(s)
Evolución Biológica , Corteza Cerebral/metabolismo , Proteínas de Homeodominio/metabolismo , Animales , Corteza Cerebral/crecimiento & desarrollo , Corteza Cerebral/patología , Embrión de Mamíferos/metabolismo , Femenino , Proteínas de Homeodominio/genética , Humanos , Macaca , Masculino , Ratones , Ratones Endogámicos C57BL , Ratones Transgénicos , Neuronas/metabolismo , Miembro 2 del Grupo A de la Subfamilia 4 de Receptores Nucleares/genética , Miembro 2 del Grupo A de la Subfamilia 4 de Receptores Nucleares/metabolismo , Embarazo , Proteínas de Dominio T Box/metabolismoRESUMEN
Genetic findings reported by our group and others showed that de novo missense variants in the KIF2A gene underlie malformations of brain development called pachygyria and microcephaly. Though KIF2A is known as member of the Kinesin-13 family involved in the regulation of microtubule end dynamics through its ATP dependent MT-depolymerase activity, how KIF2A variants lead to brain malformations is still largely unknown. Using cellular and in utero electroporation approaches, we show here that KIF2A disease-causing variants disrupts projection neuron positioning and interneuron migration, as well as progenitors proliferation. Interestingly, further dissection of this latter process revealed that ciliogenesis regulation is also altered during progenitors cell cycle. Altogether, our data suggest that deregulation of the coupling between ciliogenesis and cell cycle might contribute to the pathogenesis of KIF2A-related brain malformations. They also raise the issue whether ciliogenesis defects are a hallmark of other brain malformations, such as those related to tubulins and MT-motor proteins variants.
Asunto(s)
Cilios/genética , Cinesinas/metabolismo , Malformaciones del Desarrollo Cortical/genética , Proteínas Represoras/metabolismo , Animales , Encéfalo/metabolismo , Ciclo Celular/genética , Cilios/fisiología , Células HeLa , Humanos , Cinesinas/genética , Malformaciones del Desarrollo Cortical/metabolismo , Ratones , Microcefalia/metabolismo , Microtúbulos/metabolismo , Neurogénesis , Proteínas Represoras/genética , Huso Acromático/metabolismo , Tubulina (Proteína)/metabolismoRESUMEN
Mutations and deletions of the interleukin-1 receptor accessory protein like 1 (IL1RAPL1) gene, located on the X chromosome, are associated with intellectual disability (ID) and autism spectrum disorder (ASD). IL1RAPL1 protein is located at the postsynaptic compartment of excitatory synapses and plays a role in synapse formation and stabilization. Here, using primary neuronal cultures and Il1rapl1-KO mice, we characterized the role of IL1RAPL1 in regulating dendrite morphology. In Il1rapl1-KO mice we identified an increased number of dendrite branching points in CA1 and CA2 hippocampal neurons associated to hippocampal cognitive impairment. Similarly, induced pluripotent stem cell-derived neurons from a patient carrying a null mutation of the IL1RAPL1 gene had more dendrites. In hippocampal neurons, the overexpression of full-length IL1RAPL1 and mutants lacking part of C-terminal domains leads to simplified neuronal arborization. This effect is abolished when we overexpressed mutants lacking part of N-terminal domains, indicating that the IL1RAPL1 extracellular domain is required for regulating dendrite development. We also demonstrate that PTPδ interaction is not required for this activity, while IL1RAPL1 mediates the activity of IL-1ß on dendrite morphology. Our data reveal a novel specific function for IL1RAPL1 in regulating dendrite morphology that can help clarify how changes in IL1RAPL1-regulated pathways can lead to cognitive disorders in humans.SIGNIFICANCE STATEMENT Abnormalities in the architecture of dendrites have been observed in a variety of neurodevelopmental, neurodegenerative, and neuropsychiatric disorders. Here we show that the X-linked intellectual disability protein interleukin-1 receptor accessory protein like 1 (IL1RAPL1) regulates dendrite morphology of mice hippocampal neurons and induced pluripotent stem cell-derived neurons from a patient carrying a null mutation of IL1RAPL1 gene. We also found that the extracellular domain of IL1RAPL1 is required for this effect, independently of the interaction with PTPδ, but IL1RAPL1 mediates the activity of IL-1ß on dendrite morphology. Our data reveal a novel specific function for IL1RAPL1 in regulating dendrite morphology that can help clarify how changes in IL1RAPL1-regulated pathways can lead to cognitive disorders in humans.
Asunto(s)
Dendritas/metabolismo , Dendritas/patología , Genes Ligados a X/genética , Discapacidad Intelectual/genética , Discapacidad Intelectual/fisiopatología , Proteína Accesoria del Receptor de Interleucina-1/genética , Animales , Trastornos del Conocimiento/genética , Trastornos del Conocimiento/fisiopatología , Femenino , Hipocampo/patología , Hipocampo/fisiopatología , Masculino , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Ratas , Ratas Sprague-DawleyRESUMEN
Neurodevelopmental disorders with periventricular nodular heterotopia (PNH) are etiologically heterogeneous, and their genetic causes remain in many cases unknown. Here we show that missense mutations in NEDD4L mapping to the HECT domain of the encoded E3 ubiquitin ligase lead to PNH associated with toe syndactyly, cleft palate and neurodevelopmental delay. Cellular and expression data showed sensitivity of PNH-associated mutants to proteasome degradation. Moreover, an in utero electroporation approach showed that PNH-related mutants and excess wild-type NEDD4L affect neurogenesis, neuronal positioning and terminal translocation. Further investigations, including rapamycin-based experiments, found differential deregulation of pathways involved. Excess wild-type NEDD4L leads to disruption of Dab1 and mTORC1 pathways, while PNH-related mutations are associated with deregulation of mTORC1 and AKT activities. Altogether, these data provide insights into the critical role of NEDD4L in the regulation of mTOR pathways and their contributions in cortical development.
Asunto(s)
Complejos de Clasificación Endosomal Requeridos para el Transporte/genética , Mutación Missense , Heterotopia Nodular Periventricular/genética , Ubiquitina-Proteína Ligasas/genética , Animales , Células Cultivadas , Femenino , Humanos , Masculino , Ratones , Ubiquitina-Proteína Ligasas Nedd4 , Dominios Proteicos/genética , Proteínas Proto-Oncogénicas c-akt/metabolismo , Transducción de Señal , Serina-Treonina Quinasas TOR/metabolismo , Ubiquitina/metabolismoRESUMEN
Tubulinopathies are increasingly emerging major causes underlying complex cerebral malformations, particularly in case of microlissencephaly often associated with hypoplastic or absent corticospinal tracts. Fetal akinesia deformation sequence (FADS) refers to a clinically and genetically heterogeneous group of disorders with congenital malformations related to impaired fetal movement. We report on an early foetal case with FADS and microlissencephaly due to TUBB2B mutation. Neuropathological examination disclosed virtually absent cortical lamination, foci of neuronal overmigration into the leptomeningeal spaces, corpus callosum agenesis, cerebellar and brainstem hypoplasia and extremely severe hypoplasia of the spinal cord with no anterior and posterior horns and almost no motoneurons. At the cellular level, the p.Cys239Phe TUBB2B mutant leads to tubulin heterodimerization impairment, decreased ability to incorporate into the cytoskeleton, microtubule dynamics alteration, with an accelerated rate of depolymerization. To our knowledge, this is the first case of microlissencephaly to be reported presenting with a so severe and early form of FADS, highlighting the importance of tubulin mutation screening in the context of FADS with microlissencephaly.
Asunto(s)
Artrogriposis/genética , Malformaciones del Desarrollo Cortical/genética , Microcefalia/genética , Tubulina (Proteína)/genética , Adulto , Artrogriposis/fisiopatología , Cerebelo/fisiopatología , Femenino , Feto , Humanos , Malformaciones del Desarrollo Cortical/fisiopatología , Microcefalia/fisiopatología , Neuronas Motoras/patología , Mutación , Médula Espinal/fisiopatología , Tubulina (Proteína)/deficienciaRESUMEN
To unravel missing genetic causes underlying monogenic disorders with recurrence in sibling, we explored the hypothesis of parental germline mosaic mutations in familial forms of malformation of cortical development (MCD). Interestingly, four families with parental germline variants, out of 18, were identified by whole-exome sequencing (WES), including a variant in a new candidate gene, syntaxin 7. In view of this high frequency, revision of diagnostic strategies and reoccurrence risk should be considered not only for the recurrent forms, but also for the sporadic cases of MCD.
Asunto(s)
Mutación de Línea Germinal , Malformaciones del Desarrollo Cortical/genética , Mosaicismo , Adulto , Exoma , Femenino , Sitios Genéticos , Humanos , Masculino , Linaje , Proteínas Qa-SNARE/genéticaRESUMEN
Rett syndrome (RTT) is a rare X-linked neurodevelopmental disorder, characterized by normal post-natal development followed by a sudden deceleration in brain growth with progressive loss of acquired motor and language skills, stereotypic hand movements and severe cognitive impairment. Mutations in the methyl-CpG-binding protein 2 (MECP2) cause more than 95% of classic cases. Recently, it has been shown that the loss of Mecp2 from glia negatively influences neurons in a non-cell-autonomous fashion, and that in Mecp2-null mice, re-expression of Mecp2 preferentially in astrocytes significantly improved locomotion and anxiety levels, restored respiratory abnormalities to a normal pattern and greatly prolonged lifespan compared with globally null mice. We now report that microtubule (MT)-dependent vesicle transport is altered in Mecp2-deficient astrocytes from newborn Mecp2-deficient mice compared with control wild-type littermates. Similar observation has been made in human MECP2 p.Arg294* iPSC-derived astrocytes. Importantly, administration of Epothilone D, a brain-penetrant MT-stabilizing natural product, was found to restore MT dynamics in Mecp2-deficient astrocytes and in MECP2 p.Arg294* iPSC-derived astrocytes in vitro. Finally, we report that relatively low weekly doses of Epothilone D also partially reversed the impaired exploratory behavior in Mecp2(308/y) male mice. These findings represent a first step toward the validation of an innovative treatment for RTT.
Asunto(s)
Astrocitos/metabolismo , Proteína 2 de Unión a Metil-CpG/metabolismo , Microtúbulos/metabolismo , Vesículas Transportadoras/metabolismo , Acetilación , Animales , Arginina/metabolismo , Astrocitos/efectos de los fármacos , Línea Celular , Células Cultivadas , Epotilonas/farmacología , Histona Desacetilasa 6 , Histona Desacetilasas/metabolismo , Humanos , Masculino , Ratones , Ratones Endogámicos C57BL , Microtúbulos/efectos de los fármacos , Células Madre Pluripotentes/metabolismo , Síndrome de Rett/metabolismo , Tubulina (Proteína)/metabolismo , Moduladores de Tubulina/farmacologíaRESUMEN
Complex cortical malformations associated with mutations in tubulin genes: TUBA1A, TUBA8, TUBB2B, TUBB3, TUBB5 and TUBG1 commonly referred to as tubulinopathies, are a heterogeneous group of conditions with a wide spectrum of clinical severity. Among the 106 patients selected as having complex cortical malformations, 45 were found to carry mutations in TUBA1A (42.5%), 18 in TUBB2B (16.9%), 11 in TUBB3 (10.4%), three in TUBB5 (2.8%), and three in TUBG1 (2.8%). No mutations were identified in TUBA8. Systematic review of patients' neuroimaging and neuropathological data allowed us to distinguish at least five cortical malformation syndromes: (i) microlissencephaly (n = 12); (ii) lissencephaly (n = 19); (iii) central pachygyria and polymicrogyria-like cortical dysplasia (n = 24); (iv) generalized polymicrogyria-like cortical dysplasia (n = 6); and (v) a 'simplified' gyral pattern with area of focal polymicrogyria (n = 19). Dysmorphic basal ganglia are the hallmark of tubulinopathies (found in 75% of cases) and are present in 100% of central pachygyria and polymicrogyria-like cortical dysplasia and simplified gyral malformation syndromes. Tubulinopathies are also characterized by a high prevalence of corpus callosum agenesis (32/80; 40%), and mild to severe cerebellar hypoplasia and dysplasia (63/80; 78.7%). Foetal cases (n = 25) represent the severe end of the spectrum and show specific abnormalities that provide insights into the underlying pathophysiology. The overall complexity of tubulinopathies reflects the pleiotropic effects of tubulins and their specific spatio-temporal profiles of expression. In line with previous reports, this large cohort further clarifies overlapping phenotypes between tubulinopathies and although current structural data do not allow prediction of mutation-related phenotypes, within each mutated gene there is an associated predominant pattern of cortical dysgenesis allowing some phenotype-genotype correlation. The core phenotype of TUBA1A and TUBG1 tubulinopathies are lissencephalies and microlissencephalies, whereas TUBB2B tubulinopathies show in the majority, centrally predominant polymicrogyria-like cortical dysplasia. By contrast, TUBB3 and TUBB5 mutations cause milder malformations with focal or multifocal polymicrogyria-like cortical dysplasia with abnormal and simplified gyral pattern.
Asunto(s)
Agenesia del Cuerpo Calloso/diagnóstico , Lisencefalia/diagnóstico , Malformaciones del Desarrollo Cortical/diagnóstico , Microcefalia/diagnóstico , Mutación/genética , Tubulina (Proteína)/genética , Adolescente , Adulto , Agenesia del Cuerpo Calloso/epidemiología , Agenesia del Cuerpo Calloso/genética , Cerebelo/anomalías , Niño , Preescolar , Discapacidades del Desarrollo/diagnóstico , Discapacidades del Desarrollo/epidemiología , Discapacidades del Desarrollo/genética , Femenino , Humanos , Lactante , Lisencefalia/epidemiología , Masculino , Malformaciones del Desarrollo Cortical/epidemiología , Microcefalia/epidemiología , Microcefalia/genética , Malformaciones del Sistema Nervioso/diagnóstico , Malformaciones del Sistema Nervioso/epidemiología , Malformaciones del Sistema Nervioso/genética , Fenotipo , Adulto JovenRESUMEN
Over the last years, the critical role of cytoskeletal proteins in cortical development including neuronal migration as well as in neuronal morphology has been well established. Inputs from genetic studies were provided through the identification of several mutated genes encoding either proteins associated with microtubules (DCX, LIS1, KIF2A, KIF5C, DYNC1H1) or tubulin subunits (TUBA1A, TUBB2B, TUBB5 and TUBG1), in malformations of cortical development (MCD). We also reported the identification of missense mutations in TUBB3, the postmitotic neuronal specific tubulin, in six different families presenting either polymicrogyria or gyral disorganization in combination with cerebellar and basal ganglial abnormalities. Here, we investigate further the association between TUBB3 mutations and MCDs by analyzing the consequences of Tubb3 knockdown on cortical development in mice. Using the in utero-electroporation approach, we demonstrate that Tubb3 knockdown leads to delayed bipolar morphology and radial migration with evidence, suggesting that the neuronal arrest is a transient phenomenon overcome after birth. Silenced blocked cells display a round-shape and decreased number of processes and a delay in the acquisition of the bipolar morphology. Also, more Tbr2 positive cells are observed, although less cells express the proliferation marker Ki67, suggesting that Tubb3 inactivation might have an indirect effect on intermediate progenitor proliferation. Furthermore, we show by rescue experiments the non-interchangeability of other beta-tubulins which are unable to rescue the phenotype. Our study highlights the critical and specific role of Tubb3 on the stereotyped morphological changes and polarization processes that are required for initiating radial migration to the cortical plate.
Asunto(s)
Movimiento Celular , Corteza Cerebral/metabolismo , Malformaciones del Desarrollo Cortical/genética , Tubulina (Proteína)/metabolismo , Animales , Proteína Doblecortina , Electroporación , Femenino , Técnicas de Silenciamiento del Gen , Humanos , Malformaciones del Desarrollo Cortical/patología , Ratones , Mutación Missense , Embarazo , Isoformas de Proteínas , Tubulina (Proteína)/genéticaRESUMEN
Polymicrogyria (PMG) is a clinically heterogeneous malformation of cortical development, characterized by a loss of the normal gyral pattern that is replaced by many small and infolded gyri separated by shallow sulci that are partly fused in their depths. Causes of PMG are heterogeneous and include acquired and genetic causes. There are more than 100 syndromes possibly associated with PMG but mutations in specific genes such as SRPX2, GPR56, TUBB2B, TUBB3, NHEJ1, TUBA1A, TUBA8, and WDR62 have been reported only in a minority of patients.
Asunto(s)
Encéfalo/patología , Proteínas Portadoras/genética , Homocigoto , Malformaciones del Desarrollo Cortical/genética , Malformaciones del Desarrollo Cortical/patología , Mutación , Femenino , Feto , Humanos , Masculino , PakistánRESUMEN
The genetic causes of malformations of cortical development (MCD) remain largely unknown. Here we report the discovery of multiple pathogenic missense mutations in TUBG1, DYNC1H1 and KIF2A, as well as a single germline mosaic mutation in KIF5C, in subjects with MCD. We found a frequent recurrence of mutations in DYNC1H1, implying that this gene is a major locus for unexplained MCD. We further show that the mutations in KIF5C, KIF2A and DYNC1H1 affect ATP hydrolysis, productive protein folding and microtubule binding, respectively. In addition, we show that suppression of mouse Tubg1 expression in vivo interferes with proper neuronal migration, whereas expression of altered γ-tubulin proteins in Saccharomyces cerevisiae disrupts normal microtubule behavior. Our data reinforce the importance of centrosomal and microtubule-related proteins in cortical development and strongly suggest that microtubule-dependent mitotic and postmitotic processes are major contributors to the pathogenesis of MCD.
Asunto(s)
Dineínas Citoplasmáticas/genética , Cinesinas/genética , Microcefalia/genética , Mutación Missense , Tubulina (Proteína)/genética , Animales , Células COS , Movimiento Celular , Chlorocebus aethiops , Exoma , Estudios de Asociación Genética , Mutación de Línea Germinal , Humanos , Lisencefalia/genética , Lisencefalia/patología , Imagen por Resonancia Magnética , Malformaciones del Desarrollo Cortical/genética , Malformaciones del Desarrollo Cortical/patología , Ratones , Microcefalia/patología , Modelos Moleculares , Neuroimagen , Linaje , Análisis de Secuencia de ADNRESUMEN
The frequency of disease-related large rearrangements (referred to as copy-number mutations, CNMs) varies among genes, and search for these mutations has an important place in diagnostic strategies. In recent years, CGH method using custom-designed high-density oligonucleotide-based arrays allowed the development of a powerful tool for detection of alterations at the level of exons and made it possible to provide flexibility through the possibility of modeling chips. The aim of our study was to test custom-designed oligonucleotide CGH array in a diagnostic laboratory setting that analyses several genes involved in various genetic diseases, and to compare it with conventional strategies. To this end, we designed a 12-plex CGH array (135k; 135 000 probes/subarray) (Roche Nimblegen) with exonic and intronic oligonucleotide probes covering 26 genes routinely analyzed in the laboratory. We tested control samples with known CNMs and patients for whom genetic causes underlying their disorders were unknown. The contribution of this technique is undeniable. Indeed, it appeared reproducible, reliable and sensitive enough to detect heterozygous single-exon deletions or duplications, complex rearrangements and somatic mosaicism. In addition, it improves reliability of CNM detection and allows determination of boundaries precisely enough to direct targeted sequencing of breakpoints. All of these points, associated with the possibility of a simultaneous analysis of several genes and scalability 'homemade' make it a valuable tool as a new diagnostic approach of CNMs.
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Hibridación Genómica Comparativa/métodos , Variaciones en el Número de Copia de ADN , Exones , Estudios de Casos y Controles , Fibrosis Quística/diagnóstico , Fibrosis Quística/genética , Femenino , Duplicación de Gen , Asesoramiento Genético , Pruebas Genéticas/métodos , Hemofilia A/diagnóstico , Hemofilia A/genética , Humanos , Síndrome de Kallmann/diagnóstico , Síndrome de Kallmann/genética , Masculino , Síndrome de Rett/diagnóstico , Síndrome de Rett/genética , Análisis de Secuencia de ADN , Eliminación de SecuenciaRESUMEN
De novo mutations in the TUBA1A gene are responsible for a wide spectrum of neuronal migration disorders, ranging from lissencephaly to perisylvian pachygyria. Recently, one family with polymicrogyria (PMG) and mutation in TUBA1A was reported. Hence, the purpose of our study was to determine the frequency of TUBA1A mutations in patients with PMG and better define clinical and imaging characteristics for TUBA1A-related PMG. We collected 95 sporadic patients with non-syndromic bilateral PMG, including 54 with perisylvian PMG and 30 PMG with additional brain abnormalities. Mutation analysis of the TUBA1A gene was performed by sequencing of PCR fragments corresponding to TUBA1A-coding sequences. Three de novo missense TUBA1A mutations were identified in three unrelated patients with PMG representing 3.1% of PMG and 10% of PMGs with complex cerebral malformations. These patients had bilateral perisylvian asymmetrical PMG with dysmorphic basal ganglia cerebellar vermian dysplasia and pontine hypoplasia. These mutations (p.Tyr161His; p.Val235Leu; p.Arg390Cys) appear distributed throughout the primary structure of the alpha-tubulin polypeptide, but their localization within the tertiary structure suggests that PMG-related mutations are likely to impact microtubule dynamics, stability and/or local interactions with partner proteins. These findings broaden the phenotypic spectrum associated with TUBA1A mutations to PMG and further emphasize that additional brain abnormalities, that is, dysmorphic basal ganglia, hypoplastic pons and cerebellar dysplasia are key features for the diagnosis of TUBA1A-related PMG.
Asunto(s)
Malformaciones del Desarrollo Cortical del Grupo II/genética , Malformaciones del Desarrollo Cortical/genética , Tubulina (Proteína)/genética , Secuencia de Aminoácidos , Niño , Preescolar , Femenino , Humanos , Lactante , Masculino , Malformaciones del Desarrollo Cortical/diagnóstico , Malformaciones del Desarrollo Cortical del Grupo II/diagnóstico , Datos de Secuencia Molecular , Mutación Missense , Linaje , Estructura Terciaria de Proteína , Tubulina (Proteína)/química , Tubulina (Proteína)/metabolismoRESUMEN
Polymicrogyria is a relatively common cortical malformation characterized by multiple small gyri with abnormal cortical lamination. The pathophysiological bases are heterogeneous and include extrinsic factors and genetic causes. Recent data has emphasized the high prevalence of chromosomal rearrangements in bilateral and mainly perisylvian polymicrogyria in the context of multiple congenital abnormalities. We present here two cases of rare submicroscopic abnormalities ascertained by array-comparative genome hybridization screening of 18 patients with polymicrogyria. The first patient is an 11 year-old female with developmental delay, behavioural disturbance, postnatal microcephaly, focal seizures and temporo-occipital polymicrogyria. She presented a 7.2 Mb terminal deletion in the 6q27 region. The second patient is a 3 year-old boy with psychomotor retardation, spastic diplegia and right temporal polymicrogyria who presented a 3 Mb duplication in the 22q11.2 region. These two patients exhibited focal temporal or occipital polymicrogyria without additional brain malformations or multiple congenital abnormalities. This data suggest that patients with polymicrogyria, even focal and/or unilateral and isolated forms, should be screened for submicroscopic chromosomal rearrangements using array-CGH.
Asunto(s)
Deleción Cromosómica , Duplicación Cromosómica , Cromosomas Humanos Par 22/genética , Cromosomas Humanos Par 6/genética , Malformaciones del Desarrollo Cortical/genética , Anomalías Múltiples/genética , Niño , Preescolar , Hibridación Genómica Comparativa , Femenino , Humanos , Imagen por Resonancia Magnética , MasculinoRESUMEN
Subcortical band heterotopia (SBH) is a neuronal migration disorder usually described in females carrying heterozygous mutations in the X-linked doublecortin (DCX) gene. Hemizygous DCX mutations in males result in lissencephaly. Recently, exonic deletions of DCX resulting in a severer form of agyria have been reported. Nevertheless, rare male patients with SBH have been described with somatic mosaicism of point mutations. Here, we identified a somatic mosaicism for a deletion of exon 4 in the DCX gene in a male patient with SBH detected prenatally. This finding points to the possible implication of mosaic deletions in the DCX gene in unexplained forms of SBH and may allow for detection of SBH prenatally.