Functional analysis of ATG endoglin mutants. COS-7 cells were transfected with wild type (WT) or endoglin mutants 4A: c.-9G > A (-9), c.-9G > A & c.+1A > G (-9&+1) or c.-127C > T (-127), and 4B: c.-205A > C (-205) in the presence of HA-437/586-Endo in pDisplay (HA-437.E) to correct for transfection efficiency. After 24 h, cells were lysed and total cell lysates were subjected to western blot analysis using anti-endoglin, anti-HA or anti-actin antibodies. As a loading control, the presence of actin is included. Normalized endoglin levels relative to cotransfected HA-437/586-Endo and total actin proteins are shown in the histogram. An arbitrary value of 100 was assigned to WT endoglin. The average of six different experiments is shown in each panel.