 Each of these isoforms resides at a different chromosome location and has been cloned.Two of the main differences between the isoforms are the chain length of the hyaluronan molecules that they produce and the ease with which they can be released from the cell surface.When mammalian cells are stimulated by changes in their immediate environment (cytokines, extracellular matrix proximities), the HAS isoforms respond differently and appear to be under different control mechanisms.