Splice variants are sequences that occur naturally within the cells and tissues of individuals.
In addition, variants may have no activity at all. When a variant and the original sequence have the same or opposite activity, they may differ in various properties not directly connected to biological activity, such as stability, clearance rate, tissue and cellular localization, temporal pattern of expression, up or down regulation mechanisms, and responses to agonists or antagonists. A certain variant may be expressed mainly in one tissue, while the original sequence from which it has been varied, or another variant derived from the same sequence, may be expressed mainly in another tissue. Using well designed DNA chips, as well as other methods, it is possible to determine the differential expression pattern of various variants in various tissues. Understanding of the distribution of splice variants in various tissues is exteramely important for understanding the physiological function of the genes and for developing and targeting pharmaceuticals, as well as for diagnostic purposes.