Germline mutations of PTPN11 (SHP2) in the stem cell microenvironment

点击翻译按钮获取中文摘要

Project Summary Noonan Syndrome (NS), a developmental disorder characterized by congenital heart disease, dysmorphic facial structures, short stature, and mental retardation, is caused by germline mutations in the genes involved in the Ras signaling pathway. Patients with NS are at an increased risk of developing leukemia. The mechanisms underlying the leukemogenesis are not completely understood. NS is mainly (>50%) associated with germline heterozygous activating mutations in the protein tyrosine phosphatase PTPN11 (SHP2), and NS patients with PTPN11 mutations have the worst prognosis. Studies from our laboratory and others have established the causal role of hematopoietic cell intrinsic PTPN11 mutations in the pathogenesis of NS- associated leukemia. Notably, in the last funding period we discovered that PTPN11 activating mutations (E76K or D61G) in the bone marrow (BM) stroma, specifically Nestin-expressing and Nestin-expressing cell- derived mesenchymal stem cells and osteoprogenitors, contributed significantly to the development/ progression of hematological malignancies in mouse models. However, our understanding of the effects of PTPN11 disease mutations in the BM microenvironment is still incomplete. Our recent pilot data indicate that PTPN11 activating mutations in the peripheral nervous system (PNS) and other neural crest-derived progeny in the BM stroma also exert detrimental effects on resident HSCs  neural crest-specific PTPN11E76K mutation knock-in mice (PTPN11E76K/+/Wnt1-Cre+) developed a myeloproliferative neoplasm (MPN), and this malignancy originated from wild-type hematopoietic stem cells (HSCs). Furthermore, a donor cell-derived MPN (D-MPN) developed in PTPN11E76K/+/Wnt1-Cre+ mice transplanted with healthy BM cells. The overall objective of this application is to decipher the cellular and molecular mechanisms by which the PTPN11 mutation in neural crest-derived cells in the BM stroma induce a MPN. The central hypothesis of the proposal is that the PTPN11 mutation in these microenvironmental cells drives leukemia development by directly and/or indirectly hyperactivating resident HSCs. We plan to test this hypothesis and accomplish the objective of this application by pursuing the following three aims. 1). To identify the cell type, protein factors, and/or neurotransmitters that mediate the leukemogenic effect of PTPN11 activating mutations in the PNS and other neural crest derivatives in the BM stroma. 2). To determine the molecular mechanisms by which PTPN11 gain-of-function activating mutations deregulate the activities of the PNS and other neural crest-derived cells. 3). To validate the pathogenic effects of BM microenvironmental PTPN11 disease mutations with NS patient specimens and patient-derived cells. The research proposed in this application will not only greatly advance our understanding of the mechanisms underlying the leukemogenesis in NS, but also inform the rational design of new therapeutic interventions for preventing leukemia development in NS and improving stem cell transplantation therapy for NS-associated hematological malignancies.