A “typical” IF protein consists of an N-terminal head region, a rod region that contains four α-helical regions (helices 1A, 1B, 2A, and 2B), and a C-terminal tail region. Different isoforms of GFAP are shown: GFAP-α and GFAP-β are full-length GFAP proteins; the mRNAs encoding these two proteins differ in the 5′ UTR. GFAP-γ is encoded by an mRNA that has an alternate start site and is missing exon 1. The mRNAs encoding GFAP-δ, GFAP-ε, and GFAP-κ are generated by alternative splicing of intron 7, with variable use of exon 7+, to create proteins with different C-terminal tail sequences. Only single isoforms of α-internexin, NFL, NFM, and NFH are shown. The gray areas in NFM and NFH contain multiple phosphorylation sites. Full-length peripherin (Per58) is shown as well as Per61, a mouse isoform that retains intron 4 (96), and Per28, which is a mouse and human isoform that retains introns 3 and 4, resulting in a truncated peripherin (97).