Congenital heart defects still constitute serious medical problems. Thebackground of such defects, however, is poorly understood. Little is also known about their pattern ofinheritance. Lack of atrial and ventricular septum closures counts for a significant percentage of allcongenital heart defects. Individuals harboring such defects always suffer poor quality of life. Theonly way to help those patients is cardiac surgery. Several genes have been implicated in the processof controlling heart development. Recent studies on transgenic mice null for tolloid-like 1 (tll1) generevealed factors possibly involved in signaling pathways that, when absent, might affect heart developmentand cause problems mimicking those observed in atrial septal defects (ASDs). Lack of activity of thismetalloprotease caused incomplete closure of the septum in murine fetal hearts and led to death in mid-gestationdue to severe circulation problems. tll1 gene is located on the long arm of chromosome 4 (4q32-q33).The gene comprises of 6654 nucleotides and it encodes a protein 1013 amino acids long. Its human homologue tll1 is poorly investigated and until now no particular disorders have been linked to mutations in thisgene.

Keywords: Heart Septal Defects, Atrial - genetics, Metalloproteases - metabolism, Mice, Transgenic, Syndrome, Tolloid-Like Metalloproteinases