Comparative genomics of the human and Fugu voltage-gated calcium channel α1-subunit gene family reveals greater diversity in Fugu

Extensive search for the orthologs of 10 human voltage-gated calcium channel (VGCC) α1-subunit genes in the Fugu genome sequence revealed 21 α1-subunit genes in the compact genome of Fugu. Subtype classification of the identified Fugu α1 orthologs based on phylogenetic analysis, genomic organization and sequence comparison of the most divergent II/III loop and the C-terminal regions of the α1-subunits indicated extra copies of α1S-, α1D-, α1F-, α1A-, α1E-, α1H- and α1G-subunit genes. Phylogenetic analysis reveals that this is likely due to fish lineage specific α1-subunit subtype duplication. Sequence comparison shows that many of the structural features characteristic of VGCC and specific channel subtypes are also present in the Fugu α1-subunits. All the Fugu α1-subunits showed similar expression profile to that of the mammalian α1-subunits except for Fugu α1S, α1A, α1B and α1H which have a more widespread tissue distribution. These results indicate that Fugu, a lower vertebrate, has more extensive channel heterogeneity compared to human.