Furthermore, loss of FIG 4 (polyphosphoinositide phosphatase) and PYKfyve (FYVE finger‐containing phosphoinositide kinase), which are both involved in the synthesis of the endogenous TRPML/two‐pore channel (TPC) agonist PI(3,5)P2 (phosphatidylinositol 3,5‐bisphosphate), is associated with neurological or neurodegenerative disease phenotypes (Chow et al, 2007; Zhang et al, 2007; Zou et al, 2015), and TRPML1 activation in FIG 4−/− cells rescues lysosomal storage phenotypes (Zou et al, 2015). The gene discussed is MCOLN1; the disease is neurodegenerative disease.