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Query: UMLS:C0004134 (ataxia)
 15,886 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Over the past few years, molecular neurogenetics has developed into one of the most promising and active research fields. The new discipline applies modern molecular genetic techniques to the investigation of classical neurological disorders. In the following article, a definition of neurogenetic disease is introduced, the molecular basis of four groups of neurogenetic disorders is described and recent diagnostic developments are presented. The first group of diseases is caused by trinucleotide expansions. "Expanding" trinucleotide repeats were not known to occur in any species until about three years ago. Today, disorders such as Huntington's disease, spinocerebellar ataxia type 1, fragile X mental retardation, spinobulbar muscular atrophy and myotonic dystrophy are all known to be caused by the expansion of trinucleotides. The second group is characterized by chromosomal deletions or uniparental disomies. Lissencephaly and the Miller-Dieker syndrome, Prader-Willi and Angelman syndromes and Duchenne and Becker muscular dystrophies belong to this category. The third group includes those neurogenetic disorders that are mainly caused by point mutations such as the X-linked leukodystrophies, including Pelizaeus-Merzbacher disease and adrenoleukodystrophy, Charcot-Marie-Tooth syndrome type 1, familial forms of amyotrophic lateral sclerosis, several types of craniosynostoses and some CNS tumor syndromes. Finally, Alzheimer's and Parkinson's disease are discussed as representatives of group four, i.e. genetically heterogeneous neurological disorders.
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PMID:Molecular basis and diagnosis of neurogenetic disorders. 796 63

We report on 2 families with diffuse pachygyria and cerebellar hypoplasia, who presented hypotonia, ataxia, seizures, and developmental delay since infancy. Computed tomography (CT) and magnetic resonance imaging (MRI) revealed decreased gyral formation in the cerebral cortex and marked hypoplasia in the cerebellum. Cerebellar hypoplasia is often associated with type 2 lissencephaly; however, our cases showed no polymicrogyria, and their clinical findings were quite mild compared with those of microlissencephaly. Their characteristic phenotype suggested a new genetic syndrome, which was possibly inherited as an autosomal recessive trait.
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PMID:Diffuse pachygyria with cerebellar hypoplasia: a milder form of microlissencephaly or a new genetic syndrome? 1051 6

Loss-of-function mutations in RELN (encoding reelin) or PAFAH1B1 (encoding LIS1) cause lissencephaly, a human neuronal migration disorder. In the mouse, homozygous mutations in Reln result in the reeler phenotype, characterized by ataxia and disrupted cortical layers. Pafah1b1(+/-) mice have hippocampal layering defects, whereas homozygous mutants are embryonic lethal. Reln encodes an extracellular protein that regulates layer formation by interacting with VLDLR and ApoER2 (Lrp8) receptors, thereby phosphorylating the Dab1 signaling molecule. Lis1 associates with microtubules and modulates neuronal migration. We investigated interactions between the reelin signaling pathway and Lis1 in brain development. Compound mutant mice with disruptions in the Reln pathway and heterozygous Pafah1b1 mutations had a higher incidence of hydrocephalus and enhanced cortical and hippocampal layering defects. Dab1 and Lis1 bound in a reelin-induced phosphorylation-dependent manner. These data indicate genetic and biochemical interaction between the reelin signaling pathway and Lis1.
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PMID:Interaction of reelin signaling and Lis1 in brain development. 1457 85

Numerous evidences indicate that the phenotype of a neurodegenerative disease and its pathogenetic mechanism are only loosely linked. The phenotype is directly related to the topography of the lesions and is reproduced whatever the mechanism as soon as the same neurons are destroyed or deficient: the symptoms of Parkinson disease are mimicked by any destruction of the neurons of the substantia nigra, caused for instance by the toxin MPTP. This does not mean that idiopathic Parkinson disease is due to MPTP. In the same way, mouse lines such as Reeler, Weaver and Staggerer in which ataxia occurs spontaneously does not help to understand human ataxias: now that mutations responsible for these phenotypes have been identified, it appears that one is responsible for lissencephaly (mutation of the reelin gene) and the other two have no equivalent in man. Therapeutic attempts, however, rely on the understanding of the pathogenetic mechanisms. Introducing a mutated human transgene in the genome of an animal has, in many instances, significantly improved this understanding. Transgenic mice have proven useful in reproducing lesions seen in neurodegenerative disease such as the plaques of Alzheimer disease (in the APP mouse which has integrated the mutated gene of the amyloid protein precursor), the tau glial and neuronal accumulation (seen in cases of frontotemporal dementias due to tau mutation), the nuclear inclusions caused by CAG triplet expansion (seen in the mutation of Huntington disease and autosomal dominant spinocerebellar ataxias). These recent advances have fostered numerous therapeutic attempts. Transgenesis in drosophila and in the worm Caenorhabditis elegans have opened new possibilities in the screening of protein partners, modifier genes, and potential therapeutic molecules. However, it is also becoming clear that introducing a human mutated gene in an animal does not necessarily trigger pathogenetic cascades identical to those seen in the human disease. Human diseases have to be studied in parallel with their animal models to ensure that the model mimic at least a few original mechanisms, on which new therapeutics may be tested.
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PMID:[Animal models of neurodegenerative diseases]. 1729 28

We describe a 16-year-old girl with mental retardation, myoclonic epilepsy, ataxia, mitochondrial myopathy, sensorineural hearing loss, lactic acidosis, and MRI evidence of diffuse subcortical laminar heterotopia and agyria/pachygyria. Restriction fragment length polymorphism (RFLP) and DNA sequence analyses revealed two pathogenic mutations: a heteroplasmic m.3243A>G in muscle and blood, and a new heterozygous insertion at nt697 in the doublecortin gene (DCX), resulting in a frameshift after amino acid residue 232, with a premature stop codon at amino acid residue 244. This is yet another example of genetic "double trouble" resulting in a complex phenotype.
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PMID:Coexistence of mitochondrial and nuclear DNA mutations in a woman with mitochondrial encephalomyopathy and double cortex. 2043 51

The nuclear envelope links the cytoskeleton to structural components of the nucleus. It functions to coordinate nuclear migration and anchorage, organize chromatin, and aid meiotic chromosome pairing. Forces generated by the cytoskeleton are transferred across the nuclear envelope to the nuclear lamina through a nuclear-envelope bridge consisting of SUN (Sad1 and UNC-84) and KASH (Klarsicht, ANC-1 and Syne/Nesprin homology) proteins. Some KASH-SUN combinations connect microtubules, centrosomes, actin filaments, or intermediate filaments to the surface of the nucleus. Other combinations are used in cell cycle control, nuclear import, or apoptosis. Interactions between the cytoskeleton and the nucleus also affect global cytoskeleton organization. SUN and KASH proteins were identified through genetic screens for mispositioned nuclei in model organisms. Knockouts of SUN or KASH proteins disrupt neurological and muscular development in mice. Defects in SUN and KASH proteins have been linked to human diseases including muscular dystrophy, ataxia, progeria, lissencephaly, and cancer.
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PMID:Interactions between nuclei and the cytoskeleton are mediated by SUN-KASH nuclear-envelope bridges. 2050 27

In the past few years, the increasing accessibility of next-generation sequencing technology has translated to a number of significant advances in our understanding of brain malformations. Genes causing brain malformations, previously intractable due to their complex presentation, rarity, sporadic occurrence, or molecular mechanism, are being identified at an unprecedented rate and are revealing important insights into central nervous system development. Recent discoveries highlight new associations of biological processes with human disease including the PI3K-AKT-mTOR pathway in brain overgrowth syndromes, the trafficking of cellular proteins in microcephaly-capillary malformation syndrome, and the role of the exosome in the etiology of pontocerebellar hypoplasia. Several other gene discoveries expand our understanding of the role of mitosis in the primary microcephaly syndromes and post-translational modification of dystroglycan in lissencephaly. Insights into polymicrogyria and heterotopias show us that these 2 malformations are complex in their etiology, while recent work in holoprosencephaly and Dandy-Walker malformation suggest that, at least in some instances, the development of these malformations requires "multiple-hits" in the sonic hedgehog pathway. The discovery of additional genes for primary microcephaly, pontocerebellar hypoplasia, and spinocerebellar ataxia continue to impress upon us the significant degree of genetic heterogeneity associated with many brain malformations. It is becoming increasingly evident that next-generation sequencing is emerging as a tool to facilitate rapid and cost-effective molecular diagnoses that will be translated into routine clinical care for these rare conditions in the near future.
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PMID:Recent advances in the genetic etiology of brain malformations. 2379 31