Alternatively spliced sodium channel transcripts in brain and muscle

Abstract

Sodium (Na) channel cDNAs were synthesized from RNA isolated from rat brain, cardiac muscle, and skeletal muscle. Partial cDNAs coding for the largest cytoplasmic loop of the Na channel were amplified with PCR. Sequence analysis of these cDNAs revealed that Na channel cDNAs originally described as brain genes were also expressed in both cardiac and skeletal muscle. Some of these cDNAs were isoforms that differed by insertions or deletions and can be explained by alternative choices of a 5' splice site. Southern blot analysis of genomic DNA confirmed the presence of introns in this region of the gene. Transcripts of multiple isoforms were detected with RNase protection in brain, heart, and skeletal muscle. Several conclusions can be drawn from the data. (1) Some rat sodium channel genes are transcribed in all excitable tissues studied here: brain, cardiac muscle, and skeletal muscle. (2) Each of these three tissues expresses multiple sodium channel genes. (3) Alternative splicing of sodium channel transcripts occurs in these tissues. (4) Expression of multiple genes and alternative splicing of the transcripts is responsible for at least seven different sodium channel mRNAs in skeletal muscle.

The newborn rabbit sino‐atrial node expresses a neuronal type I‐like Na+ channel.

“…We used TTX, 1s-CTX and Cd2+ in order to match the affinities of these Nae channel blockers to those already described for known isoforms. these Na+ currents may be mediated by type I Na+ channels, or possibly an alternatively spliced variant similar to those reported to occur by Schaller, Krzemien, McKenna & Caldwell (1992).…”

Modulatory Proteins Can Rescue a Trafficking Defective Epileptogenic Nav1.1 Na+Channel Mutant

“…We used the shorter (1998 aa) splice variant isoform of the human Na v 1.1 Na ϩ channel (Noda et al, 1986;Schaller et al, 1992), which could be the predominant Na v 1.1 variant expressed in brain (Schaller et al, 1992) and that we have used previously for functional studies (Oliveira et al, 2004;Mantegazza et al, 2005a,b). According to the different numeration, the mutation that we studied would be M1852T in the longer isoforms used by (Spampanato et al, 2004).…”

“…The cDNA for human Na v 1.1 Na ϩ channel ␣ subunit (hNa v 1.1) was provided by Dr. Jeff Clare (GlaxoSmithKline, Stevenage, Herts, UK) and encodes the shorter splice variant isoform of 1998 aa (Noda et al, 1986;Schaller et al, 1992); we numbered Na v 1.1 protein sequence accordingly. We generated the chimeric construct YFPhNa v 1.1 (N-terminal tagging of hNa v 1.1 with yellow fluorescent protein) ( Fig.…”

A rescuable folding defective Nav1.1 (SCN1A) sodium channel mutant causes GEFS+: Common mechanism in Nav1.1 related epilepsies?

“…The cDNA of the human Na v 1.1 Na + channel α subunit (hNa v 1.1) was provided by Dr. Jeff Clare (GlaxoSmithKline, Stevenage, Herts, U.K.) and encodes the shorter splice variant isoform of 1998 amino acids that could be the predominant Na v 1.1 variant expressed in brain (Schaller et al, 1992). hNa v 1.1 has a high rearrangement rate when propagated in bacteria; we subcloned hNa v 1.1 cDNA into the plasmid pCDM8 (Mantegazza et al, 2005a) because in our experience it was able to stabilize the cDNA of several Na + channel α subunits (Mantegazza et al, 2001;Mantegazza et al, 2005b), and we propagated it in TOP10/P3 or MC1061/P3 E.Coli (Invitrogen) grown at 28°C for >48h in order to minimize the rearrangements; the entire coding sequence was sequenced after each propagation.…”