JAK2 is a gene that provides instructions for making a protein involved in cell signaling. This protein plays a crucial role in the body's ability to produce blood cells by transmitting signals from various growth factors and hormones. When functioning properly, JAK2 helps regulate blood cell production and maintain healthy blood levels. Mutations in the JAK2 gene can lead to various blood disorders, including polycythemia vera and essential thrombocythemia. These conditions result in the overproduction of blood cells, which can increase the risk of complications such as blood clots. Understanding JAK2 is important for diagnosing and treating these disorders effectively.