Complete loss of P/Q calcium channel activity caused by a CACNA1A missense mutation carried by patients with episodic ataxia type 2.

Familial hemiplegic migraine, episodic ataxia type 2 (EA2), and spinocerebellar ataxia type 6 are allelic disorders of the CACNA1A gene (coding for the alpha(1A) subunit of P/Q calcium channels), usually associated with different types of mutations (missense, protein truncating, and expansion, respectively). However, the finding of expansion and missense mutations in patients with EA2 has blurred this genotype-phenotype correlation. We report the first functional analysis of a new missense mutation, associated with an EA2 phenotype-that is, T-->C transition of nt 4747 in exon 28, predicted to change a highly conserved phenylalanine residue to a serine at codon 1491, located in the putative transmembrane segment S6 of domain III. Patch-clamp recording in HEK 293 cells, coexpressing the mutagenized human alpha(1A-2) subunit, together with human beta(4) and alpha(2)delta subunits, showed that channel activity was completely abolished, although the mutated protein is expressed in the cell. These results indicate that a complete loss of P/Q channel function is the mechanism underlying EA2, whether due to truncating or to missense mutations.

[1]  C. Fletcher,et al.  Dystonia and cerebellar atrophy in Cacna1a null mice lacking P/Q calcium channel activity , 2001, FASEB journal : official publication of the Federation of American Societies for Experimental Biology.

[2]  Kinya Ishikawa,et al.  Spinocerebellar Ataxia Type 6 Mutation Alters P-type Calcium Channel Function* , 2000, The Journal of Biological Chemistry.

[3]  A. Olsen,et al.  A fine physical map of the CACNA1A gene region on 19p13.1-p13.2 chromosome. , 2000, Gene.

[4]  R. Tsien,et al.  Ablation of P/Q-type Ca(2+) channel currents, altered synaptic transmission, and progressive ataxia in mice lacking the alpha(1A)-subunit. , 1999, Proceedings of the National Academy of Sciences of the United States of America.

[5]  K. Friend,et al.  Detection of a novel missense mutation and second recurrent mutation in the CACNA1A gene in individuals with EA-2 and FHM. , 1999 .

[6]  J. Nutt,et al.  A novel nonsense mutation in CACNA1A causes episodic ataxia and hemiplegia , 1999, Neurology.

[7]  N. Battistini,et al.  A new CACNA1A gene mutation in acetazolamide-responsive familial hemiplegic migraine and ataxia , 1999, Neurology.

[8]  A. Novelletto,et al.  CAG repeat instability, cryptic sequence variation and pathogeneticity: evidence from different loci. , 1999, Philosophical transactions of the Royal Society of London. Series B, Biological sciences.

[9]  Y. Mori,et al.  Direct Alteration of the P/Q-Type Ca2+ Channel Property by Polyglutamine Expansion in Spinocerebellar Ataxia 6 , 1999, The Journal of Neuroscience.

[10]  A. Vighetto,et al.  High prevalence of CACNA1A truncations and broader clinical spectrum in episodic ataxia type 2 , 1999, Neurology.

[11]  K. Stauderman,et al.  Functional Consequences of Mutations in the Human α1A Calcium Channel Subunit Linked to Familial Hemiplegic Migraine , 1999, The Journal of Neuroscience.

[12]  E. Timin,et al.  Ca2+ channel block and inactivation: common molecular determinants. , 1998, Trends in pharmacological sciences.

[13]  R. Kraus,et al.  Familial Hemiplegic Migraine Mutations Change α1ACa2+ Channel Kinetics* , 1998, The Journal of Biological Chemistry.

[14]  Bertil Hille,et al.  Voltage-Gated Ion Channels and Electrical Excitability , 1998, Neuron.

[15]  R. Kraus,et al.  Molecular mechanism of use-dependent calcium channel block by phenylalkylamines: role of inactivation. , 1997, Proceedings of the National Academy of Sciences of the United States of America.

[16]  S. Nelson,et al.  Progressive ataxia due to a missense mutation in a calcium-channel gene. , 1997, American journal of human genetics.

[17]  D. Geschwind,et al.  Spinocerebellar ataxia type 6 , 1997, Neurology.

[18]  R. Ophoff,et al.  Episodic ataxia type 2 (EA2) and spinocerebellar ataxia type 6 (SCA6) due to CAG repeat expansion in the CACNA1A gene on chromosome 19p. , 1997, Human molecular genetics.

[19]  W. Catterall,et al.  Molecular Determinants of High Affinity Phenylalkylamine Block of l-type Calcium Channels in Transmembrane Segment IIIS6 and the Pore Region of the α1Subunit* , 1997, The Journal of Biological Chemistry.

[20]  Dennis E Bulman,et al.  Familial Hemiplegic Migraine and Episodic Ataxia Type-2 Are Caused by Mutations in the Ca2+ Channel Gene CACNL1A4 , 1996, Cell.

[21]  P. Ince,et al.  The expression of neuronal voltage-dependent calcium channels in human cerebellum. , 1995, Brain research. Molecular brain research.

[22]  J. Hell,et al.  Immunochemical identification and subcellular distribution of the alpha 1A subunits of brain calcium channels , 1995, The Journal of neuroscience : the official journal of the Society for Neuroscience.

[23]  G. Ebers,et al.  Mapping the gene for acetazolamide responsive hereditary paryoxysmal cerebellar ataxia to chromosome 19p. , 1995, Human molecular genetics.

[24]  J. Luebke,et al.  Exocytotic Ca2+ channels in mammalian central neurons , 1995, Trends in Neurosciences.

[25]  D. Glavač,et al.  Sensitivity of single-strand conformation polymorphism and heteroduplex method for mutation detection in the cystic fibrosis gene. , 1994, Human molecular genetics.

[26]  C. Harris1,et al.  Eye Movements in a Familial Vestibulocerebellar Disorder , 1993, Neuropediatrics.

[27]  T. Sekiya,et al.  Rapid and sensitive detection of point mutations and DNA polymorphisms using the polymerase chain reaction. , 1989, Genomics.

[28]  F. Chédru,et al.  Recurrence of the T666M calcium channel CACNA1A gene mutation in familial hemiplegic migraine with progressive cerebellar ataxia. , 1999, American journal of human genetics.

[29]  K. Friend,et al.  Detection of a novel missense mutation and second recurrent mutation in the CACNA1A gene in individuals with EA-2 and FHM , 1999, Human Genetics.

[30]  R. Kraus,et al.  Familial hemiplegic migraine mutations change alpha1A Ca2+ channel kinetics. , 1998, The Journal of biological chemistry.

[31]  William B. Dobyns,et al.  Autosomal dominant cerebellar ataxia (SCA6) associated with small polyglutamine expansions in the α1A-voltage-dependent calcium channel , 1997, Nature Genetics.

[32]  C. Ucla,et al.  Dinucleotide repeat polymorphism in the human RFX1 gene. , 1994, Human Molecular Genetics.