Molecular NeuroscienceResearch PaperDifferential expression of exon 5 splice variants of sodium channel α subunit mRNAs in the developing mouse brain
Section snippets
Tissue collection and RNA extraction
Brains of male C57BL/6J mice were collected at seven postnatal ages (n=3 for each age group) and divided into four regions: cerebellum, thalamus, hippocampus and cortex. All animal experiments conformed to Australian Code of Practice for the Care and Use of Animals for Scientific Purposes, and every effort was taken to reduce the number of animals used and to minimize their suffering. Tissue samples were frozen in liquid nitrogen and stored at −80 °C. Total RNA was extracted from the brain
Relative expression of exon 5 splice variants
In the mouse Scn1a gene, the region corresponding to human exon 5N contains several stop codons and is not flanked by a canonical splice site sequence at the 3′ end (Fig. 1B), suggesting that the “neonatal” Scn1a mRNA is unlikely to be expressed in mice. The 5N and 5A coding exons in mouse Scn2a, Scn3a and Scn8a genes are flanked by canonical splice sites (not shown), suggesting that alternative splicing of exon 5 occurs in the respective pre-mRNAs. All mouse sodium channel α subunit genes
Discussion
In this study we have examined developmental and regional expression of exon 5 splice variants of sodium channel α subunit mRNAs in the mouse brain. The results showed that mouse Scn1a mRNA is expressed only as the 5A isoform, unlike its human ortholog. This result, together with the published data showing a wide range of variability in the proportion of the 5N SCN1A mRNA in adult human population (Heinzen et al., 2007), suggests that the “neonatal” isoform of SCN1A-encoded protein is not
Acknowledgments
We thank Jane Howard and Damian F. J. Purcell for help with agarose gel analysis.
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