Dentatorubral and pallidoluysian atrophy expansion of an unstable CAG trinucleotide on chromosome 12p
ABSTRACT Dentatorubral and pallidoluysian atrophy (DRPLA) is an autosomal dominant neurodegenerative disorder characterized by combined systemic degeneration of the dentatofugal and pallidofugal pathways. We investigated a candidate gene and found that DRPLA patients had an expanded CAG trinucleotide repeat in a gene on the short arm of chromosome 12. The repeat size varied from 7−23 in normal individuals. In patients one allele was expanded to between 49−75 repeats or occasionally even more. Expansion was usually associated with paternal transmission and only occasionally with maternal transmission. Repeat size showed a close correlation with age of onset of symptoms and disease severity. We conclude that DRPLA is the seventh genetic disorder known to be associated with expansion of an unstable trinucleotide repeat.
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ABSTRACT: Pallister Killian syndrome (OMIM: # 601803) is a rare multisystem disorder typically caused by tissue limited mosaic tetrasomy of chromosome 12p (isochromosome 12p). The clinical manifestations of Pallister Killian syndrome are variable with the most common findings including craniofacial dysmorphia, hypotonia, cognitive impairment, hearing loss, skin pigmentary differences and epilepsy. Isochromosome 12p is identified primarily in skin fibroblast cultures and in chorionic villus and amniotic fluid cell samples and may be identified in blood lymphocytes during the neonatal and early childhood period. We performed genomic expression profiling correlated with interphase fluorescent in situ hybridization and single nucleotide polymorphism array quantification of degree of mosaicism in fibroblasts from 17 Caucasian probands with Pallister Killian syndrome and 9 healthy age, gender and ethnicity matched controls. We identified a characteristic profile of 354 (180 up- and 174 down-regulated) differentially expressed genes in Pallister Killian syndrome probands and supportive evidence for a Pallister Killian syndrome critical region on 12p13.31. The differentially expressed genes were enriched for developmentally important genes such as homeobox genes. Among the differentially expressed genes, we identified several genes whose misexpression may be associated with the clinical phenotype of Pallister Killian syndrome such as downregulation of ZFPM2, GATA6 and SOX9, and overexpression of IGFBP2.PLoS ONE 10/2014; 9(10):e108853. · 3.53 Impact Factor
Article: Genetic cerebellar ataxias.[Show abstract] [Hide abstract]
ABSTRACT: This review broadly covers the commoner genetic ataxias, concentrating on their clinical features. Over the last two decades there has been a potentially bewildering profusion of newly described genetic ataxias. However, at least half of dominant ataxias (SCAs) are caused by (CAG)n repeat expansions resulting in expanded polyglutamine tracts (SCAs 1, 2, 3, 6, 7, 17, and DRPLA), although of the remainder only SCAs 8, 10, 12, 14, 15/16, and 31 are frequent enough that the described phenotype is probably representative. Though the SCAs can be difficult to separate clinically, variations in prevalence in different populations, together with various clinical and radiological features, at least help to order the pretest probabilities. The X-linked disorder, fragile-X tremor ataxia syndrome occurs in fragile-X permutation carriers, and typically causes a late-onset ataxia-plus syndrome. The recessive ataxias are not named systematically: The most frequent are Friedreich, ataxia telangiectasia, ARSACS, AOA1 and 2, and the various POLG syndromes. Although rare, several other recessive disorders such as AVED are potentially treatable and should not be missed. Another group of genetic ataxias are the dominant episodic ataxias, of which EA1 and EA2 are the most important. Lastly, the neurologist's role in ongoing management, rather than just diagnosis, is addressed.Seminars in Neurology 07/2014; 34(3):280-92. · 1.78 Impact Factor
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ABSTRACT: The human glutamate receptor delta 2 gene (GRID2) shares 90% homology with the orthologous mouse gene. The mouse Grid2 gene is involved with functions of the cerebellum and spontaneous mutation of Grid2 leads to a spinocerebellar ataxia-like phenotype. To investigate whether such mutations occur in humans, we screened for mutations in the coding sequence of GRID2 in 24 patients with familial or sporadic spinocerebellar ataxia and in 52 normal controls. We detected no point mutations or insertion/deletion mutations in the 16 exons of GRID2. However, a polymorphic 4 nucleotide deletion (IVS5-121_-118 GAGT) and two single nucleotide polymorphisms (c.1251G>T and IVS14-63C>G) were identified. The frequency of these polymorphisms was similar between spinocerebellar ataxia patients and normal controls. These data indicate that spontaneous mutations do not occur in GRID2 and that the incidence of spinocerebellar ataxia in humans is not associated with GRID2 mutation or polymorphisms.Neural Regeneration Research 05/2014; 9(10):1068-74. · 0.23 Impact Factor