Despite the emerging role of TRPML1 in a range of cellular functions, including cationic lysosomal homeostasis, cell repair (Colletti et al., 2012; Li et al., 2016; Miedel et al., 2008; Venkatachalam et al., 2008; Vergarajauregui et al., 2008; Wong et al., 2012; Xu et al., 2006; Zhang et al., 2016) and, more recently, aging and cancer (Jung et al., 2019; Xu et al., 2019), the time course of Mcoln1/TRPML1 expression during the development of living tissue has not been tracked. Here, MCOLN1 is linked to cancer.