WASF1 and melanoma: To obtain B16-F1 melanoma cell clones with abolished WRC function, as an alternative to Sra1 and PIR121 (also known as CYFIP2; referred to collectively hereafter as Sra1/PIR121) double knockout (KO) cells or WAVE protein KOs (Schaks et al., 2018; Tang et al., 2020), we initially disrupted the Nckap1 gene encoding Nap1 (Fig. S1A), which was hitherto thought to be essential for WRC function in this cell type (Steffen et al., 2006, 2004).