The diverse properties of intermediate filaments, compared with the conserved microtubule and actin filament proteins, could be responsible for the distinguishing molecular shapes of different cell types. In nerve cells, for example, the expressions of different types of IFs relates to the change in shape during development. Early stages of development in neurons is marked by the outgrowth of neurites and axons contributing to the cells asymmetric shape. During these transitions in cell shape, only homopolymer type III intermediate filaments, such as those with<unk> , are made. As the nerve cell matures, these type III IFs are replaced by more complex type IV neurofilaments expanding the diameter of axons in order to attain normal velocities of action potentials. The exact function of<unk>  is unknown. Expression of<unk>  in development is greatest during the axonal growth phase and decreases postnatally, which suggests a role in neurite elongation and axonal guidance during development. Expression is also increased after axonal injury, such as peripheral axotomy in motor neurons and dorsal root ganglia. This upregulation implies that<unk>  may also play a role in axon regeneration. However, experiments using<unk>  depleted PC12 cells and<unk>  knockout mice provide proof that the majority of neurons have no requirement of<unk>  for axonal guidance and regrowth. PC12 cells lacking<unk>  showed no defects in neurite outgrowth and<unk>  knockout mice develop normally with no anatomical abnormalities or different phenotypes. In these experiments,<unk>  deficiency did produce an upregulation of α-internexin, indicating the possibility that this type IV intermediate filament makes up for the loss of<unk> . Future studies of double knockout mice for both the<unk>  and α-internexin genes might address this theory. However, while most<unk>  knockout mice displayed normal neuron growth, its absence did affect development of a subset of unmyelinated sensory axons. In such mice, there was a "34% reduction in the number of L5 unmyelinated sensory fibers that correlated with a decreased binding of the lectin IB4." PRPH Localization PRPH is located on the q12-q13 region of the human chromosome 12.
Peripherin
Tetraspanin
Dystrophin
Neurofilament light polypeptide
Parkin 
Apamin
Clathrin
Internexin