Voltage-dependent calcium channels mediate the entry of calcium ions into excitable cells, and are also involved in a variety of calcium-dependent processes, including muscle contraction, hormone or neurotransmitter release and gene expression. Calcium channels are multi-subunit complexes composed of alpha-1, beta, alpha-2/delta, and gamma subunits. The channel activity is directed by the pore-forming alpha-1 subunit whereas the others act as auxiliary subunits regulating this activity. The distinctive properties of the calcium channel types are related primarily to the expression of a variety of alpha-1 isoforms, alpha-1A, B, C, D, E, and S. The CACNA1A gene encodes the alpha-1A subunit, which is predominantly expressed in neuronal tissue. Mutations in this gene are associated with two neurological disorders, familial hemiplegic migraine and episodic ataxia 2. Episodic ataxia 1 is caused by mutations in the KCNA1 gene.
The CACNA1A gene (47 exons) spans ~300 kb of genomic DNA and is located on 19p13.2, 13.3 Mb from the p-telomere. The P279-B3 CACNA1A probemix contains probes for 30 of the 47 exons of the CACNA1A gene (two probes for exon 1). Furthermore one flanking probe located 2 Mb downstream of CACNA1A has been included. KCNA1 (2 exons) spans ~8.4 kb of genomic DNA and is located on 12p13.32, 4.9 Mb from the p-telomere. Probes for both exons are included. In addition, the P279 probemix contains 11 reference probes detecting several different autosomal chromosomal locations.
This SALSA® MLPA® probemix is designed to detect deletions/duplications of one or more sequences in the aforementioned gene(s) in a DNA sample. Heterozygous deletions of recognition sequences should give a 35-50% reduced relative peak height of the amplification product of that probe. Note that a mutation or polymorphism in the sequence detected by a probe can also cause a reduction in relative peak height, even when not located exactly on the ligation site! In addition, some probe signals are more sensitive to sample purity and small changes in experimental conditions. Therefore, deletions and duplications detected by MLPA should always be confirmed by other methods. Not all deletions and duplications detected by MLPA will be pathogenic; users should always verify the latest scientific literature when interpreting their findings. We have no information on what percentage of defects in these genes is caused by deletions/duplications of complete exons. Finally, note that most defects in this gene are expected to be small (point) mutations which will not be detected by this SALSA® MLPA® test.