IF assembly can then proceed in this manner infinitely. It should be noted that the above scheme is somewhat tentative and lacks firm evidence. It is not clear for example exactly which domains are responsible for tetramers binding end to end. The three cytoskeletal components have distinct sub-cellular localisations. Microfilaments are enriched in a layer known as the cell cortex , immediately beneath the plasma membrane, and in cell projections such as microvilli.
Microtubules extend from the perinucleus towards the cell periphery.
The plus ends of MTs point to the cell periphery. IFs are distributed in a similar pattern to MTs except where cells are in contact where the IFs are enriched. IFs and MTs are excluded from the actively expanding leading edge of the moving or ruffling cell. In some situations a co-localisation of the cytoskeletal systems is seen. For example, neurofilaments and MT co-localise in the axon of neurons where specific cross links are made between the two systems.