RASA2 and juvenile myelomonocytic leukemia: NF1 is a Ras-GTPase activating protein (GAP) and its loss is associated with increased formation of Ras-GTP leading to increased downstream signaling.[7] Somatic NF1 mutations have been identified as pathogenic events in other malignancies like juvenile myelomonocytic leukemia, lung cancer and melanoma.