Newly characterised 5' and 3' regions of CACNA1A gene harbour mutations associated with Familial Hemiplegic Migraine and Episodic Ataxia.
The CACNA1A gene codes for the alpha(1A) pore-forming subunit of Ca(2+) voltage-gated Cav2.1 channels. CACNA1A mutations are responsible for Familial Hemiplegic Migraine (FHM) type 1, Episodic Ataxia (EA) type 2 and Spinocerebellar Ataxia type 6. The structure of the human gene includes, at present, 49 exons; however almost nothing is known about the 5' regulatory region, and there is now evidence suggesting the presence of additional exons at the 3' of the gene. The 892 bp fragment upstream of exon 1 and its deletion mutants were characterised for their transcriptional activity by using luciferase as a reporter gene. The 3' region was analysed by Rapid Amplification of the cDNA 3' End. Both regions were screened for mutations in a series of FHM and EA patients by SSCP and sequencing. At the 5' end of the gene a minimal promoter region was identified within the first 497 bp from ATG. By screening a larger fragment for mutations, the 5 bp deletion (g.-757_-753delCTTTC) was identified in a FHM patient. The deletion significantly increased the transcriptional activity, most likely due to the removal of half a turn of the DNA helix, changing the orientation of downstream binding sites for transcriptional factors. At the 3' end of the gene a new exon 48, followed by a strong poly-A signal, was identified as well as a new splice variant. The 5 bp insertion (g.38429_38430insCTTTT) in this exon was found in an EA patient. The two new regions can open the way for the study of human CACNA1A gene expression regulation and can be sites of mutations associated with FHM or EA phenotypes.
Veneziano
Liana
L
Istituto di Neurobiologia e Medicina Molecolare, CNR, Via Fosso del Cavaliere, Rome, Italy. liana.veneziano@artov.inmm.cnr.it
Guida
Serena
S
Mantuano
Elide
E
Bernard
Paola
P
Tarantino
Patrizia
P
Boccone
Loredana
L
Hisama
Fuki M
FM
Carrera
Paola
P
Jodice
Carla
C
Frontali
Marina
M
D000704:Analysis of Variance; D001259:Ataxia / Q000097:blood / Q000235:genetics*; D015220:Calcium Channels / Q000235:genetics*; D045744:Cell Line, Tumor; D019295:Computational Biology / Q000379:methods; D004252:DNA Mutational Analysis; D005091:Exons / Q000235:genetics*; D006801:Humans; D007558:Italy; D020325:Migraine with Aura / Q000097:blood / Q000235:genetics*; D008969:Molecular Sequence Data; D009447:Neuroblastoma / Q000378:metabolism; D010641:Phenotype; D017384:Sequence Deletion / Q000235:genetics*; D020864:Calcium Channels, N-Type
D015220:Calcium Channels; C105656:CACNA1A protein, human; D020864:Calcium Channels, N-Type