Abstract
The CACNA1A gene codes for the α1A pore-forming subunit of Ca2+ 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.
Abbreviations:
FHM (Familial Hemiplegic Migraine), EA (Episodic Ataxia), SCA (Spinocerebellar Ataxia), RACE (Rapid Amplification of Complementary DNA Ends), DMEM (Dulbecco Modified Eagle's Medium), ANOVA (Analysis of variance), TSS (Transcription Start Site), IRF (Interferon Regulating Factor), MRI (Magnetic Resonance Image), EEG (Electroencephalogram), wt (Wildtype), VGCC (Voltage-gated calcium channel), MIM (Mendelian Inheritance in Man.)Keywords
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Article info
Publication history
Accepted:
August 20,
2008
Received in revised form:
June 26,
2008
Received:
November 27,
2007
Identification
Copyright
© 2008 Elsevier B.V. Published by Elsevier Inc. All rights reserved.
