SMN2 and embryonal carcinoma: Using a murine embryonic carcinoma cell line P19, a direct effect of SMN loss on apoptotic cell death was observed.24 In SMN knocked down differentiated P19 cell neurons the cell death was noticed as caspase dependent, which is confirmed by using pan-caspase inhibitor ZVAD-fmk, which led to a significant reduction in the rate of apoptosis in SMN knocked down cells.