We took advantage of expressing the mouse ortholog in human cells to distinguish the expression of endogenous ATOH1 from that of Atoh1. For the tests in human cancer cell lines, we used the MCC14.2 cell line, which is derived from MCC and has strongly reduced expression of ATOH1. Surprisingly, Atoh1 overexpression failed to activate endogenous human ATOH1 expression in the MCC14.2 cell line (Figure 3C), despite the virtually complete conservation of the two proteins. The gene discussed is ATOH1; the disease is Merkel cell skin cancer.