Abstract:The aim of this study was to analyze the biological role of different transforming growth factor-$\beta$ (TGF$\beta$) receptor splice variants in ovarian carcinoma (OC). Specific receptor variant knockouts (KO) were prepared using the CRISPR/Cas9 genome editing system in two OC cell lines, T$\beta$RI variant 1 (T$\beta$RIv1) KO in ES-2 cells and T$\beta$RII variant 1 (T$\beta$RIIv1) KO in OVCAR-8 cells. Control and KO cells were compared by proteomic analysis, functional tests, analysis of epithelial-mesenchymal transition (EMT) drivers, and Western blot of signaling proteins. Proteomic analysis revealed significant changes in protein pathways in the KO cells. T$\beta$RIv1 KO resulted in a significant reduction in both cellular motility and invasion, while T$\beta$RIIv1 KO significantly reduced cellular motility and increased Reactive Oxygen Species (ROS) production. Both receptor variant KOs reduced MET protein levels. Of the EMT drivers, a significant decrease in TWIST protein expression, and increase in SNAIL protein and MALAT1 mRNA levels were observed in the T$\beta$RIIv1 KO compared to control. A significant decrease in JNK1 and JNK2 activation was found in the T$\beta$RIv1 KO compared to control cells. These findings provide new insight regarding the biological role of the TGF$\beta$ receptor variants in the biology and potentially the progression of OC.