Investigation of IRS1 and IRS2 function in normal hematopoiesis and myelodysplastic syndrome using murine models and human hematopoietic stem cells

Abstract

Hematopoiesis is a process finely regulated by cytokines and growth factors. The regulation of these molecules depends, among other factors, on the action of cytoplasmic adapter proteins, such as insulin receptor substrates (IRS). IRS activation promotes the recruitment of effector proteins involved in the regulation of JAK/STAT, PI3K/AKT/mTOR and MAPK signaling. These signaling pathways are involved in normal hematopoiesis and are dysregulated in hematological malignancies, such as myelodysplastic syndrome, which is characterized by ineffective hematopoiesis and peripheral blood cytopenias. Previous study conducted by our research group indicated that IRS1 and IRS2 are differentially expressed in hematological malignancies, including myelodysplastic syndromes and acute leukemias. Our group also demonstrated that IRS2 is recruited during the process of erythroid, megakaryocytic and granulocytic differentiation; and participates in the aberrant signaling induced by the JAK2V617F mutation. However, the role of IRS1 and IRS2 in signal transduction of hematopoietic growth factor receptors and their role in hematopoietic cell differentiation and malignant transformation remains poorly explored. Thus, the present study aim to investigate the participation of IRS1 and IRS2 proteins in normal and myelodysplastic hematopoiesis using murine models and human hematopoietic stem cells. Murine Irs1 or Irs2 knockout models and animals undergoing pharmacological inhibition of Irs1/Irs2 will be used for in vivo hematopoiesis evaluation. To evaluate the effects of inhibition of these proteins on the phenotype of normal human hematopoietic progenitors, CD34+ cells silenced for IRS1 or IRS2 will be evaluated through functional assays including differentiation, colony formation, proliferation and apoptosis. In order to investigate the expression profile of genes involved in IRS-mediated signaling in a model of neoplasia with ineffective hematopoiesis, expression of IRS1, IRS2 and related genes will be investigated and compared between CD34+ cells from healthy donors and myelodysplastic syndrome patients, through PCR array. (AU)