Complex sentence: Interestingly, GFAP and other type III IF proteins cannot assemble with keratins, the type I and II intermediate filaments: in cells that express both proteins, two separate intermediate filament networks form, which can allow for specialization and increased variability.
Split into simpler sentences: Interestingly, GFAP and other type III IF proteins cannot assemble with keratins, the type I and II intermediate filaments. In cells that express both proteins, two separate intermediate filament networks form, which can allow for specialization and increased variability.