Hematopoiesis

In our body, hematopoietic stem cells continuously generate billions of new blood cells of more than ten specialized blood cell lineages (multipotency) while sustaining their number constant life-long (self-renewal). We investigate the molecular control of these stem cell fate decisions, which are orchestrated by a complicated interplay of extrinsic signals, signal transduction pathways, gene expression regulation and pre- / post-translational influences. Hematopoietic stem cells are rare cells in adult bone marrow and enrichment of these cells by multi-parameter fluorescence-activated cell sorting (FACS) and analyses at the single cell level are essential for understanding their biology in detail. Modern imaging approaches (continuous cell tracking) combined with latest molecular and cellular technologies should elucidate these mechanisms in high sequential resolution at the single cell level during differentiation. Hematopoiesis is a massive regenerative process that is hierarchically organized with the stem cell at the apex of the hierarchy. Marker-defined stem cells and progenitor stages with restricted lineage potential can be prospectively isolated – from mouse and human origin. However, the hematopoietic hierarchy is far better defined in mice than in humans – and a better resolution of the heterogenic mixture of human stem and progenitor cells is urgently awaited for improved usage of these valuable cells for cell and gene therapeutic approaches.

Hematopoietic differentiation hierarchy (from Rieger and Schroeder, Cold Spring Harb Perspect Biol 4:a008250, 2012)

Mammary gland development

The mammary epithelium is composed of ductal, alveolar, and myoepithelial cells, all can be generated from a single mammary stem cell. As a part of our attempt to reveal the basic mechanism which govern the transition of a single stem cell into a fully functional organ, we are investigating the function of selected genes (coding or non-coding) which may regulate mammary gland stem cells self-renewal and differentiation during the four stages of the mammary developmental cycle (virgin, pregnant, lactating, and involution). Our goal is to develop new approaches that will be based on cutting edge technology that will allow us to evaluate the role of individual genes on mammary gland development as well as their involvement during breast cancer oncogenesis, with the hope to find new regulatory genes serving as potential targets for therapy.

Colon carcinoma-initiating stem cells

Colorectal cancer is the second leading cause of cancer related death. Current knowledge suggests that colon cancer is a stem-cell driven malignancy, in which only a small population of cells, termed as cancer-initiating stem cells (CSCs), are able to initiate and sustain tumor growth. Worthy to mention is that CSCs not necessarily arise only from normal stem cells. Similar to normal stem cells, CSCs have the ability to self-renew and to generate the cellular heterogeneity of the tumor by differentiation. CSCs are thought to be resistant to conventional anticancer therapy and so provoke tumor relapse after treatment. Moreover, CSCs share properties of metastasis-initiating cells. CSCs have been initially identified in acute myeloid leukemia, and subsequently in solid human malignancies. Despite the description of some surface markers, only an insufficient purity of colorectal CSCs can be achieved and their biology remains largely undefined. The link of functional behavior at the single cell level with prospective identification of CSCs by surface markers and in vivo functional read-outs helped to identify a more aggressive colon cancer subpopulation, and determined its molecular composition (proteome) in order to identify new vulnerables for targeted cellular therapies and diagnostic markers.

Technologies:

• Long-term time-lapse imaging and single cell tracking
• Multiparameter FACS analyses and cell sorting
• Multiplex intracellular cytometry for signaling and RNA expression
• Clonal in vitro differentiation assays (CFU, mammosphere assay, tumorsphere assays)
• Single cell genomic and transcriptomic analyses
• Organ reconstitution assays by transplantations (congenic and xenograft)
• Orthotopic transplantation tumor models