MAPT and Alzheimer disease: Furthermore, the enhanced expression of a short form of TG2 (sTG2), an alternatively spliced transcript lacking GTPase activity that maintains poor crosslinking activity and thus has a pro-apoptotic property, has been reported in AD patients,22, 91, 92 whereas TG2 is not a biochemical marker for AD disease because no colocalization of TG2 with tau or amyloid-β deposits is found in neocortex sections.93