DOCK9 is a 2,069 amino acid protein that localizes to the intracytoplasmic membrane and contains one PH domain, one DHR-1 domain and one DHR-2 domain. Expressed in a variety of tissues with highest expression in placenta and heart and lower expression in lung, kidney, brain and skeletal muscle, Zizimin-1 functions as a guanine nucleotide-exchange factor (GEF) that specifically activates Cdc42 by exchanging bound GDP for free GTP. Four isoforms of Zizimin-1 exist due to alternative splicing events. The gene encoding Zizimin-1 maps to human chromosome 13, which houses over 400 genes, such as BRCA2 and RB1, and comprises nearly 4% of the human genome. Trisomy 13, also known as Patau syndrome, is deadly and the few who survive past one year suffer from permanent neurologic defects, difficulty eating and vulnerability to serious respiratory infections.