Identification of a novel SCA14 mutation in a Dutch autosomal dominant cerebellar ataxia family.
ABSTRACT To report a Dutch family with autosomal dominant cerebellar ataxia (ADCA) based on a novel mutation in the PRKCG gene.
The authors studied 13 affected members of the six-generation family. After excluding the known spinocerebellar ataxia (SCA) genes, a combination of the shared haplotype approach, linkage analysis, and genealogic investigations was used. Exons 4 and 5 of the candidate gene, PRKCG, were sequenced.
Affected subjects displayed a relatively uncomplicated, slowly progressive cerebellar syndrome, with a mean age at onset of 40.8 years. A focal dystonia in two subjects with an onset of disease in their early 20s suggests extrapyramidal features in early onset disease. Significant linkage to a locus on chromosome 19q was found, overlapping the SCA-14 region. Based on the recent description of three missense mutations in the PRKCG gene, located within the boundaries of the SCA-14 locus, we sequenced exons 4 and 5 of this gene and detected a novel missense mutation in exon 4, which involves a G-->A transition in nucleotide 353 and results in a glycine-to-aspartic acid substitution at residue 118.
A SCA-14-linked Dutch ADCA family with a novel missense mutation in the PRKCG gene was identified.
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ABSTRACT: Spinocerebellar ataxia type 14 (SCA14) is an autosomal-dominant ataxia caused by point mutations of the Protein Kinase C Gamma gene. In addition to slowly progressive cerebellar ataxia, it is characterised by dystonia and myoclonus. With scant neuropathological data and no detailed neurophysiological examinations little is known on extracerebellar consequences of SCA14 related cerebellar pathology. To this end, we here delineate clinical phenomenology and neurophysiology of four German SCA14 families. Detailed clinical examination including ataxia severity evaluation by means of the Scale for the Assessment and Rating of Ataxia (SARA) was carried out in 9 affected family members (mean age 49.8 years ± 14.4 SD). Motor thresholds (MT), the contralateral silent period (CSP), short interval intracortical inhibition (SICI) and intracortical facilitation (ICF), interhemispheric inhibition (IHI) and short afferent inhibition (SAI) were determined using transcranial magnetic stimulation (TMS). Somatosensory evoked potentials (SEP) of the median nerve, and acoustic and visual evoked potentials (AEP, VEP) were also performed. Most patients reported symptoms since early childhood. There was a positive correlation between age and SARA scores (r = .721, P < 0.05). Patients had cerebellar ataxia, mild dystonia (focal, task-specific or segmental), subtle pyramidal signs and myoclonus. SICI increased with increasing conditioning pulse intensities in healthy controls but not in patients. Other neurophysiological parameters did not differ between groups. SCA14 is a slowly progressive ataxia associated with mild dystonia and myoclonus. Reduced SICI reflects abnormalities of intracortical inhibitory circuits.The Cerebellum 09/2013; 13(1). DOI:10.1007/s12311-013-0522-7 · 2.86 Impact Factor
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ABSTRACT: The protein kinase C γ (PKCγ) undergoes multi-step activation and participates in various cellular processes in Purkinje cells. Perturbations in its phosphorylation state, conformation or localization can disrupt kinase signaling, such as in Spinocerebellar ataxia type 14 (SCA14) that is caused by missense mutations in PRKCG encoding for PKCγ. We previously showed that SCA14 mutations enhance PKCγ membrane translocation upon stimulation due to an altered protein conformation. Since the faster translocation did not result in an increased function, we examined how SCA14 mutations induce this altered conformation of PKCγ and what the consequences of this conformational change are on PKCγ life cycle. Here, we show that SCA14-related PKCγ-V138E exhibits an exposed C-terminus as shown by FRET-FLIM microscopy in living cells, indicative of its partial unfolding. This conformational change was associated with faster PMA-induced translocation and accumulation of fully phosphorylated PKCγ in the insoluble fraction, which could be rescued by co-expressing PDK1 kinase, that normally triggers PKCγ autophosphorylation. We propose that the SCA14 mutation V138E causes unfolding of the C1B domain and exposure of the C-terminus of the PKCγ-V138E molecule, resulting in a decrease of functional kinase in the soluble fraction. This article is protected by copyright. All rights reserved.Journal of Neurochemistry 10/2013; DOI:10.1111/jnc.12491 · 4.24 Impact Factor
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ABSTRACT: There is an increasing awareness of the role of the cerebellum not only in motor, but also in cognitive and emotional functions. Spinocerebellar ataxia type 14 (SCA14) is an autosomal dominant hereditary ataxia characterized by a relatively pure cerebellar phenotype. Cognitive impairment has been reported in studies with phenotype descriptions of SCA14, but previous studies have been small without control groups, and no homogeneous and systematic test panel has been used. The objective of this study was to thoroughly characterize the neuropsychological profile in ten Norwegian SCA14 subjects compared to unaffected family members and population norm data. Ten SCA14 subjects and ten intrafamilial unaffected age- and education-matched controls from two Norwegian families were included. The unaffected intrafamilial controls included six first degree relatives, two second degree relatives, and two spouses. General intellectual ability, memory, visuoperceptive skills, psychomotor speed, executive functions, depression and anxiety were examined using internationally standardized tests, with minimal need for manual response to avoid motor bias. No significant cognitive deficit was found in SCA14 subjects compared to intrafamilial controls. Verbal IQ, verbal executive function and psychomotor speed tended to be reduced in affected subjects, but previously reported non-verbal executive dysfunction was not confirmed in this study. Only subtle cognitive impairment was found in SCA14 affected subjects. The current findings do not confirm earlier reports of cognitive dysfunction in SCA14, but does shows a mild impairment in specific verbal executive functions. Genotypic differences may partly account for this discrepancy, and further studies on larger materials are needed to verify the findings.BMC Neurology 11/2013; 13(1):186. DOI:10.1186/1471-2377-13-186 · 2.49 Impact Factor