Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0004134 (ataxia)
 15,886 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Point mutations of the CACNA1A gene coding for the alpha 1A voltage-dependent calcium channel subunit are responsible for familial hemiplegic migraine (FHM) and episodic ataxia type 2 (EA2). In addition, expansions of the CAG repeat motif at the 3' end of the gene, smaller than those responsible for dynamic mutation disorders, were found in patients with a progressive spinocerebellar ataxia, named SCA6. In the present work, the analysis of two new families with small CAG expansions of the CACNA1A gene is presented. In one family, with a clinical diagnosis of EA2, a CAG23 repeat allele segregated in patients showing different interictal symptoms, ranging from nystagmus only to severe progressive cerebellar ataxia. No additional mutations in coding and intron-exon junction sequences in disequilibrium with the CAG expansion were found. In the second family, initially classified as autosomal dominant cerebellar ataxia of unknown type, an inter-generational allele size change showed that a CAG20 allele was associated with an EA2 phenotype and a CAG25 allele with progressive cerebellar ataxia. These results show that EA2 and SCA6 are the same disorder with a high phenotypic variability, at least partly related to the number of repeats, and suggest that the small expansions may not be as stable as previously reported. A refinement of the coding and intron-exon junction sequences of the CACNA1A gene is also provided.
 ...
PMID:Episodic ataxia type 2 (EA2) and spinocerebellar ataxia type 6 (SCA6) due to CAG repeat expansion in the CACNA1A gene on chromosome 19p. 930 78

We describe a family with severe progressive cerebellar ataxia involving the trunk, the extremities, and speech. The proband, who has prominent atrophy of the cerebellum, shown by magnetic resonance imaging, was confined to a wheelchair at the age of 44 years. Two sons have episodes of vertigo and ataxia that are not responsive to acetazolamide. Quantitative eye-movement testing showed a consistent pattern of abnormalities localizing to the cerebellum. Genotyping suggested linkage to chromosome 19p, and SSCP showed an aberrant migrating fragment in exon 6 of the calcium-channel gene CACNA1A, which cosegregated with the disease. Sequencing of exon 6 identified a G-->A transposition in one allele, at nucleotide 1152, resulting in a predicted glycine-to-arginine substitution at codon 293. The CAG-repeat expansion associated with spinocerebellar ataxia 6 was not present in any family members. This family is unique in having a non-CAG-repeat mutation that leads to severe progressive ataxia. Since a great deal is known about the function of calcium channels, we speculate on how this missense mutation leads to the combination of clinical symptoms and signs.
 ...
PMID:Progressive ataxia due to a missense mutation in a calcium-channel gene. 934 7

With the recent report of mutations in the calcium channel gene CACNA1A in two families with episodic ataxia type 2, we investigated a patient with nonfamilial episodic vertigo and ataxia responsive to acetazolamide for similar mutations. Single-strand conformation polymorphism (SSCP) analysis of exon 23 identified an extra band in the patient that was not present in other relatives or in normal controls. Exon 23 of the patient showed a spontaneous C to T substitution at position 4410 resulting in an early stop codon. Patients with nonfamilial episodic ataxia may respond to acetazolamide and may have mutations in CACNA1A.
 ...
PMID:De novo mutation in CACNA1A caused acetazolamide-responsive episodic ataxia. 960 Jul 39

Since a few years, many mutations in genes encoding voltage-dependent ion channels have been identified. The related disorders are quoted as "channelopathies". These mutations are responsible for several skeletal muscle, brain, heart or kidney diseases. Abnormal calcium channels genes are responsible for hypokaleamic periodic paralysis (CACNA1S) as well as some forms of ataxia, cerebellar degeneration and migraine (CACNA1A). The preliminary studies of the recently discovered calcium channelopathies are undergoing. Both in vitro and in vivo studies of the diseased genes should help to the understanding of the related pathologies as well as to extend our knowledge of calcium channel function. In addition, autoantibodies against calcium channels are retrieved in some autoimmune diseases, such as Lambert-Eaton myasthenic syndrome (LEMS). Complementary studies are necessary to identify the precise implication of calcium channels in these auto-immune channelopathies.
 ...
PMID:[Physiopathology of calcium channels: identification of calcium channelopathies]. 975 59

The SCA6 mutation, a small expansion of a CAG repeat in a calcium channel gene CACNA1A, was identified in three pedigrees. Point mutations in other parts of the gene CACNA1A were excluded and new clinical features of SCA6 reported--namely, central positional nystagmus and episodic ataxia responsive to acetazolamide. The three allelic disorders, episodic ataxia type 2, familial hemiplegic migraine, and SCA6, have overlapping clinical features.
 ...
PMID:Spinocerebellar ataxia type 6 with positional vertigo and acetazolamide responsive episodic ataxia. 977 87

Familial hemiplegic migraine (HM) is an autosomal dominant migraine with aura. In 20% of HM families, HM is associated with a mild permanent cerebellar ataxia (PCA). The CACNA1A gene encoding the alpha1A subunit of P/Q-type voltage-gated calcium channels is involved in 50% of unselected HM families and in all families with HM/PCA. Four CACNA1A missense mutations have been identified in HM: two in pure HM and two in HM/PCA. Different CACNA1A mutations have been identified in other autosomal dominant conditions: mutations leading to a truncated protein in episodic ataxia type 2 (EA2), small expansions of a CAG trinucleotide in spinocerebellar ataxia type 6 and also in three families with EA2 features, and, finally, a missense mutation in a single family suffering from episodic ataxia and severe progressive PCA. We screened 16 families and 3 nonfamilial case patients affected by HM/PCA for specific CACNA1A mutations and found nine families and one nonfamilial case with the same T666M mutation, one new mutation (D715E) in one family, and no CAG repeat expansion. Both T666M and D715E substitutions were absent in 12 probands belonging to pure HM families whose disease appears to be linked to CACNA1A. Finally, haplotyping with neighboring markers suggested that T666M arose through recurrent mutational events. These data could indicate that the PCA observed in 20% of HM families results from specific pathophysiologic mechanisms.
 ...
PMID:Recurrence of the T666M calcium channel CACNA1A gene mutation in familial hemiplegic migraine with progressive cerebellar ataxia. 991 47

The recent discovery that familial hemiplegic migraine, episodic ataxia type 2, and spinocerebellar ataxia type 6 are allelic disorders caused by different mutations in CACNA1A, a calcium-channel-encoding gene, adds to a growing list of channelopathies causing paroxysmal neurologic disturbance and progressive neurodegeneration. Calcium channelopathies in the central nervous system provide a model to study the important roles that calcium channels play in neuronal function.
 ...
PMID:Calcium channelopathies in the central nervous system. 1039 79

Different aspects of expanded polyglutamine tracts and of their pathogenetic role are taken into consideration here. (i) The (CAG)n length of wild-type alleles of the Huntington disease gene was analysed in instability-prone tumour tissue from colon cancer patients to test whether the process leading to the elongation of alleles towards the expansion range involves single-unit stepwise mutations or larger jumps. The analysis showed that length changes of a single unit had a relatively low frequency. (ii) The observation of an expanded spinocerebellar ataxia (SCA)1 allele with an unusual pattern of multiple CAT interruptions showed that cryptic sequence variations are critical not only for sequence length stability but also for the expression of the disease phenotype. (iii) Small expansions of the (CAG)n sequence at the CACNA1A gene have been reported as causing SCA6. The analysis of families with SCA6 and episodic ataxia type 2 showed that these phenotypes are, in fact, expressions of the same disorder caused either by point mutations or by small (CAG)n expansions. A gain of function has been hypothesized for all proteins containing an expanded polyglutamine stretch, including the alpha 1A subunit of the voltage-gated calcium channel type P/Q coded by the CACNA1A gene. Because point mutations at the same gene with similar phenotypic consequences are highly unlikely to have this effect, an alternative common pathogenetic mechanism for all these mutations, including small expansions, can be hypothesized.
 ...
PMID:CAG repeat instability, cryptic sequence variation and pathogeneticity: evidence from different loci. 1043 11

The P/Q-type Ca(2+) channel alpha(1A) subunit gene (CACNA1A) was cloned on the short arm of chromosome 19 between the markers D19S221 and D19S179 and found to be responsible for Episodic Ataxia type 2, Familial Hemiplegic Migraine and Spinocerebellar Ataxia type 6. This region was physically mapped by 11 cosmid contigs spanning about 1. 4Mb, corresponding to less than 70% of the whole region. The cosmid contig used to characterize the CACNA1A gene accounted only for the coding region of the gene lacking, therefore, the promoter and possible regulation regions. The present study improves the physical map around and within the CACNA1A by giving a complete cosmid or BAC contig coverage of the D19S221-D19S179 interval. A number of new STSs, whether polymorphic or not, were characterized and physically mapped within this region. Four ESTs were also assigned to cosmids belonging to specific contigs.
 ...
PMID:A fine physical map of the CACNA1A gene region on 19p13.1-p13.2 chromosome. 1060 97

Autosomal-dominant cerebellar ataxias (ADCA) may present as progressive or paroxysmal disorders. While the progressive ataxias have been named spinocerebellar ataxias (SCA), the paroxysmal disorders are designated episodic ataxias (EA). Until now, three different mutational mechanisms resulting in distinctive pathogenesis have been identified. The first type of mutation present in SCA1, SCA2, SCA3, and SCA7 is an expanded CAG repeat in genes of unknown function that are translated into proteins with expanded polyglutamine tracts. A common ultrastructural feature of these disorders is the formation of neuronal intranuclear inclusions (NII) harboring the expanded disease proteins and a variety of other proteins. The pathogenic role of these inclusions has yet to be clarified. A second group of disorders is the result of mutations in genes that code for ion channels. In EA-1, a disorder characterized by episodes of ataxia provoked by movement and startle, missense mutations in a potassium channel gene, KCNA1, have been found. Patients with EA-2, another form of paroxysmal ataxia, carry nonsense mutations of the gene encoding the alpha1A voltage-dependent calcium channel subunit, CACNA1A, that are predicted to result in truncated channel proteins. In SCA6, a progressive ataxia, an expanded CAG repeat in the 3' translated region of the CACNA1A gene, has been found. The third type of mutation is an untranslated CTG expansion resembling the mutation found in myotonic dystrophy. It is associated with a progressive ataxia, SCA8.
 ...
PMID:The molecular biology of the autosomal-dominant cerebellar ataxias. 1092 70


1 2 3 4 5 6 7 8 9 10 Next >>