GATA4 and heart disorder: Thus, it seems more likely that the absence of heart disease in some 8p23.1 duplication syndrome probands [5], four members of a family with a 133 kb microduplication of the GATA4 gene [25] and seven individuals with a 4.37 Mb duplication of 8p23.1 to 8p22 that included GATA4 [26], is more likely to reflect non-penetrance rather than the existence of a further heart disease gene between REPP and REPD.