RASGEF1A (RasGEF domain family, member 1A) is a 481 amino acid guanine-nucleotide exchange factor (GEF) for H-Ras, K-Ras, and N-Ras. RASGEF1A may also play a role in cell migration. RASFEG1A is highly expressed in spinal chord and brain and contains one N-terminal Ras-GEF domain and one Ras-GEF domain. The gene that encodes RASGEF1A maps to human chromosome 10, which contains over 800 genes and 135 million nucleotides, making up nearly 4.5% of the human genome. PTEN is an important tumor suppressor gene located on chromosome 10 and, when defective, causes a genetic predisposition to cancer development known as Cowden syndrome.