Because blebbing requires RhoA activation23 (Supplementary Fig. 6a, b) and volume sensitive chloride channels are modulated by RhoA24,25, we examined how optogenetic regulation of RhoA activity alters the spatial localization of SWELL1 using SWELL1-iRFP-expressing MDA-MB-231 breast cancer cells. The gene discussed is RHOA; the disease is breast carcinoma.