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Sharma, Nutan

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Sharma, Nutan
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    Evidence for Altered Basal Ganglia-Brainstem Connections in Cervical Dystonia
    (Public Library of Science, 2012) Kuster, John K.; Woodman, Sandra C.; Kirlic, Namik; Multhaupt-Buell, Trisha J.; Makris, Nikos; Parent, Martin; Sjalander, Greta; Breiter, Henry; Blood, Anne; Makhlouf, Miriam Louise; Sudarsky, Lewis; Breiter, Hans C.; Sharma, Nutan
    Background: There has been increasing interest in the interaction of the basal ganglia with the cerebellum and the brainstem in motor control and movement disorders. In addition, it has been suggested that these subcortical connections with the basal ganglia may help to coordinate a network of regions involved in mediating posture and stabilization. While studies in animal models support a role for this circuitry in the pathophysiology of the movement disorder dystonia, thus far, there is only indirect evidence for this in humans with dystonia. Methodology/Principal Findings: In the current study we investigated probabilistic diffusion tractography in DYT1-negative patients with cervical dystonia and matched healthy control subjects, with the goal of showing that patients exhibit altered microstructure in the connectivity between the pallidum and brainstem. The brainstem regions investigated included nuclei that are known to exhibit strong connections with the cerebellum. We observed large clusters of tractography differences in patients relative to healthy controls, between the pallidum and the brainstem. Tractography was decreased in the left hemisphere and increased in the right hemisphere in patients, suggesting a potential basis for the left/right white matter asymmetry we previously observed in focal dystonia patients. Conclusions/Significance: These findings support the hypothesis that connections between the basal ganglia and brainstem play a role in the pathophysiology of dystonia.
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    Disease onset in X-linked dystonia-parkinsonism correlates with expansion of a hexameric repeat within an SVA retrotransposon in TAF1
    (National Academy of Sciences, 2017) Bragg, D. Cristopher; Mangkalaphiban, Kotchaphorn; Vaine, Christine; Kulkarni, Nichita J.; Shin, David; Yadav, Rachita; Dhakal, Jyotsna; Ton, Mai-Linh; Cheng, Anne; Russo, Christopher T.; Ang, Mark; Acuña, Patrick; Go, Criscely; Franceour, Taylor N.; Multhaupt-Buell, Trisha; Ito, Naoto; Müller, Ulrich; Hendriks, William; Breakefield, Xandra; Sharma, Nutan; Ozelius, Laurie
    X-linked dystonia-parkinsonism (XDP) is a neurodegenerative disease associated with an antisense insertion of a SINE-VNTR-Alu (SVA)-type retrotransposon within an intron of TAF1. This unique insertion coincides with six additional noncoding sequence changes in TAF1, the gene that encodes TATA-binding protein–associated factor-1, which appear to be inherited together as an identical haplotype in all reported cases. Here we examined the sequence of this SVA in XDP patients (n = 140) and detected polymorphic variation in the length of a hexanucleotide repeat domain, (CCCTCT)n. The number of repeats in these cases ranged from 35 to 52 and showed a highly significant inverse correlation with age at disease onset. Because other SVAs exhibit intrinsic promoter activity that depends in part on the hexameric domain, we assayed the transcriptional regulatory effects of varying hexameric lengths found in the unique XDP SVA retrotransposon using luciferase reporter constructs. When inserted sense or antisense to the luciferase reading frame, the XDP variants repressed or enhanced transcription, respectively, to an extent that appeared to vary with length of the hexamer. Further in silico analysis of this SVA sequence revealed multiple motifs predicted to form G-quadruplexes, with the greatest potential detected for the hexameric repeat domain. These data directly link sequence variation within the XDP-specific SVA sequence to phenotypic variability in clinical disease manifestation and provide insight into potential mechanisms by which this intronic retroelement may induce transcriptional interference in TAF1 expression.
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    Dopa-Responsive Dystonia: Functional Analysis of Single Nucleotide Substitutions within the 5’ Untranslated GCH1 Region
    (Public Library of Science, 2013) Armata, Ioanna A.; Balaj, Leonora; Kuster, John K.; Zhang, Xuan; Tsai, Shelun; Armatas, Andreas A.; Multhaupt-Buell, Trisha J.; Soberman, Roy; Breakefield, Xandra; Ichinose, Hiroshi; Sharma, Nutan
    Background: Mutations in the GCH1 gene are associated with childhood onset, dopa-responsive dystonia (DRD). Correct diagnosis of DRD is crucial, given the potential for complete recovery once treated with L-dopa. The majority of DRD associated mutations lie within the coding region of the GCH1 gene, but three additional single nucleotide sequence substitutions have been reported within the 5’ untranslated (5’UTR) region of the mRNA. The biologic significance of these 5’UTR GCH1 sequence substitutions has not been analyzed. Methodology/Principal Findings Luciferase reporter assays, quantitative real time PCR and RNA decay assays, combined with bioinformatics, revealed a pathogenic 5’UTR GCH1 substitution. The +142C>T single nucleotide 5’UTR substitution that segregates with affected status in DRD patients, substantially attenuates translation without altering RNA expression levels or stability. The +142C>T substitution disrupts translation most likely by creating an upstream initiation start codon (uAUG) and an upstream open reading frame (uORF). Conclusions/Significance: This is the first GCH1 regulatory substitution reported to act at a post-transcriptional level, increasing the list of genetic diseases caused by abnormal translation and reaffirming the importance of investigating potential regulatory substitutions in genetic diseases.
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    Thalamic Volume Is Reduced in Cervical and Laryngeal Dystonias
    (Public Library of Science, 2016) Waugh, Jeff L.; Kuster, John K.; Levenstein, Jacob M.; Makris, Nikos; Multhaupt-Buell, Trisha J.; Sudarsky, Lewis; Breiter, Hans C.; Sharma, Nutan; Blood, Anne
    Background: Dystonia, a debilitating movement disorder characterized by abnormal fixed positions and/or twisting postures, is associated with dysfunction of motor control networks. While gross brain lesions can produce secondary dystonias, advanced neuroimaging techniques have been required to identify network abnormalities in primary dystonias. Prior neuroimaging studies have provided valuable insights into the pathophysiology of dystonia, but few directly assessed the gross volume of motor control regions, and to our knowledge, none identified abnormalities common to multiple types of idiopathic focal dystonia. Methods: We used two gross volumetric segmentation techniques and one voxelwise volumetric technique (voxel based morphometry, VBM) to compare regional volume between matched healthy controls and patients with idiopathic primary focal dystonia (cervical, n = 17, laryngeal, n = 7). We used (1) automated gross volume measures of eight motor control regions using the FreeSurfer analysis package; (2) blinded, anatomist-supervised manual segmentation of the whole thalamus (also gross volume); and (3) voxel based morphometry, which measures local T1-weighted signal intensity and estimates gray matter density or volume at the level of single voxels, for both whole-brain and thalamus. Results: Using both automated and manual gross volumetry, we found a significant volume decrease only in the thalamus in two focal dystonias. Decreases in whole-thalamic volume were independent of head and brain size, laterality of symptoms, and duration. VBM measures did not differ between dystonia and control groups in any motor control region. Conclusions: Reduced thalamic gross volume, detected in two independent analyses, suggests a common anatomical abnormality in cervical dystonia and spasmodic dysphonia. Defining the structural underpinnings of dystonia may require such complementary approaches.
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    Deep brain stimulation for medically refractory life-threatening status dystonicus in children
    (Journal of Neurosurgery Publishing Group (JNSPG), 2012) Walcott, Brian; Nahed, Brian; Kahle, Kristopher T.; Duhaime, Ann-Christine; Sharma, Nutan; Eskandar, Emad
    Generalized dystonic syndromes may escalate into persistent episodes of generalized dystonia known as status dystonicus that can be life-threatening due to dystonia-induced rhabdomyolysis and/or respiratory compromise. Treatment of these conditions usually entails parenteral infusion of antispasmodic agents and sedatives and occasionally necessitates a medically induced coma for symptom control. The authors report a series of 3 children who presented with medically intractable, life-threatening status dystonicus and were successfully treated with bilateral pallidal deep brain stimulation. Bilateral globus pallidus internus stimulation appears to be effective in the urgent treatment of medically refractory and life-threatening movement disorders.
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    Dopamine Receptor and Gα(olf) Expression in DYT1 Dystonia Mouse Models during Postnatal Development
    (Public Library of Science, 2015) Zhang, Lin; McCarthy, Deirdre M.; Sharma, Nutan; Bhide, Pradeep G.
    Background: DYT1 dystonia is a heritable, early-onset generalized movement disorder caused by a GAG deletion (ΔGAG) in the DYT1 gene. Neuroimaging studies and studies using mouse models suggest that DYT1 dystonia is associated with dopamine imbalance. However, whether dopamine imbalance is key to DYT1 or other forms of dystonia continues to be debated. Methodology/Principal Findings We used Dyt1 knock out (Dyt1 KO), Dyt1 ΔGAG knock-in (Dyt1 KI), and transgenic mice carrying one copy of the human DYT1 wild type allele (DYT1 hWT) or human ΔGAG mutant allele (DYT1 hMT). D1R, D2R, and Gα(olf) protein expression was analyzed by western blot in the frontal cortex, caudate-putamen and ventral midbrain in young adult (postnatal day 60; P60) male mice from all four lines; and in the frontal cortex and caudate putamen in juvenile (postnatal day 14; P14) male mice from the Dyt1 KI and KO lines. Dopamine receptor and Gα(olf) protein expression were significantly decreased in multiple brain regions of Dyt1 KI and Dyt1 KO mice and not significantly altered in the DYT1 hMT or DYT1 hWT mice at P60. The only significant change at P14 was a decrease in D1R expression in the caudate-putamen of the Dyt1 KO mice. Conclusion/Significance We found significant decreases in key proteins in the dopaminergic system in multiple brain regions of Dyt1 KO and Dyt1 KI mouse lines at P60. Deletion of one copy of the Dyt1 gene (KO mice) produced the most pronounced effects. These data offer evidence that impaired dopamine receptor signaling may be an early and significant contributor to DYT1 dystonia pathophysiology.