GATA4 and heart septal defect: Furthermore, the GATA4 mutation prevents the physical interaction between GATA4 and TBX5, a T-box protein responsible for a subset of syndromic cardiac septal defects.141,142 Overexpression of GATA4 is associated with cardiac hypertrophy, where directly it regulates the expression of several cardiac specific proteins, such as troponin C and I and myosin light chain-3 (Figure 5e).