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Nav2.2 ( also known as Scn7A, Na-G) is expressed in astrocytes of rat CNS.
The mammalian sodium channel isoforms that have been identified thus far can be subdivided into three main groups. The type 1 channels (Nav1.x) share significant sequence similarity with each other,4 and all but one have been functionally expressed in exogenous systems. The type 2 channels (Nav2.x) are approximately 50% identical to the type 1 channels, with significant differences in regions that are critical for channel function.  None of these channels have been expressed in an exogenous system before 1999, so that it was not possible to draw any conclusions about the properties of these channels before 1999. 
Scn7A may represent the same gene as Scn6A, since only one full-length cDNA has been isolated for these two genes from any single species. 
The phylogenetic relationship of mammalian voltage-gated sodium channel alpha subunit genes, including Scn7A can be found at .
See figure 1 in Goldin 2000  for a transmembrane folding diagram displaying the structure of a generic voltage gated sodium alpha subunit.
In the rat brain, Nav2.2 can be found in astrocytes and PNS (DRG).