The brain in Down syndrome (TRISOMY 21).

Down syndrome (DS) is the most common genetic birth defect associated with mental retardation. The mechanism(s) underlying the neuropathology of DS is not completely understood. Different hypotheses have been advanced to explain this mystery, including the gene dosage effect, the amplified developmental instability, and the molecular misreading concept. Overexpression of genes residing in chromosome 21 has been assumed to be a central point in the neuropathology of DS, although reports disagreeing with this notion have also been published. In addition, an accumulating body of evidence indicates that genes located on other chromosomes are also involved in the process. DS thus appears to be a disease process involving numerous gene products and this interaction and interplay in the final analysis determines the outcome of the disease. In this regard, transcription factors, reactive oxygen species and apoptosis related proteins are viewed as potential candidates that play a significant role in the disease process. Therapeutic modalities that target these factors including antioxidants and caspase inhibitors might have some benefit in alleviating the symptoms of DS.