•C Comparison of proteolytic activity similar to the experiment of panel A, except that equimolar concentrations of PAPP-A2 and PAPP-A2 (A1033V) were used. The variant from Family 1, carrying a frameshift mutation N-terminal to the proteolytic domain of PAPP-A2, did not show any detectable expression. All gels and blots are representative of three independent experiments. 