BFSCI Research

Ihor Lemischka, Ph.D., Director

The focus of my research is to understand the molecular and cellular nature of the undifferentiated stem cell “states”, and how such states are altered during a change in cell fate.  The underlying rationale for our studies is that the complement of gene-products and their inter-relationships that exist in stem cells accounts for their remarkable abilities to balance self-renewal and differentiation decision processes.  We study both adult and embryonic stem (ES) cells, primarily from the mouse, but also from the human.  As a first step, we have comprehensively identified most, if not all gene-products that are expressed in highly purified hematopoietic stem cell (HSC).  We performed similar analyses in mouse ES cells.  Such molecular “signatures” provide parts-lists that are available to the stem cells.  The challenge has been to functionally address the roles that these molecules play in mediating the biological properties of HSC and ES cells.  Further, we would like to understand how these molecular components are “wired” into regulatory signaling and transcriptional networks.  To explore these issues we have utilized a number of global gene-expression perturbation technologies, such as inhibitory short hairpin RNA (shRNA).  We have successfully down regulated the expression levels of candidate regulatory molecules in both HSC and ES cells.  A number of these play crucial regulatory roles in processes such as self-renewal, proliferation, and differentiation.  We have further developed strategies that allow the analyses of cell-fate change dynamics at multiple biochemical and molecular levels in response to defined and precisely controlled changes in the expression levels of key regulatory molecules.  These strategies have provided the first in-depth view of how a cell-fate decision actually occurs at the transcriptional, post-transcriptional, translational, and post-translational levels.  An important aspect of our overall efforts is computational and quantitative analyses.  We anticipate that our approach will yield a systems biology level description and understanding of stem cell decision processes.  This in turn, will have profound implications in future efforts focused on applying basic stem cell research in translational as well as clinical contexts.

Stuart Aaronson, M.D.

Dr. Aaronson is an internationally recognized cancer biologist, who in early studies established the transformation-competent but replication defective nature of mammalian sarcoma viruses and molecularly cloned many of their oncogenes. He and colleagues implicated retroviral-related oncogenes in human cancer through investigations including the initial detection of their expression in human tumors and critical contributions to the demonstration of their involvement in human cancer. His investigations of the v-sis oncogene established the first normal function of an oncogene and the role of oncogenes in growth factor signaling. His discovery of erbB2 as a v-erbB-related gene amplified in a human breast carcinoma and demonstration of its transforming properties paved the way for targeted therapies directed against its product.

Penny Asbell, M.D.

Dr. Asbell's basic and clinical research has made significant contributions to the development and subsequent approval of numerous medical devices and pharmaceuticals. As principal investigator in countless studies sponsored by the National Eye Institute and industry, she has participated in the development of pharmaceuticals that has included pivotal treatments for ocular herpes, corneal ulcers, and dry eyes. She has been an innovator in the evolution of refractive surgeries, including radial keratotomy, the intrastromal corneal ring and excimer laser photo-refractive keratectomy.

Margaret Baron, M.D.- Ph.D.

Our research program combines multiple complementary approaches to study the mechanisms by which cell fate decisions are regulated in stem and progenitor cells, with a focus on hematopoiesis and vascular development. We used a novel explant culture assay to show that signaling interactions between endoderm and mesoderm play a role in hematopoietic and vascular induction in the early mouse embryo. One such signal, Indian hedgehog (Ihh), may function, in part, through upregulation of Bone Morphogenetic Protein 4 (BMP4). We are interested in analyzing the hematopoietic and vascular defects in mice carrying mutations in genes encoding components of these signaling pathways and in testing small molecule Hh agonists and antagonists in mouse and human stem/progenitor cell systems, with a view toward translation to clinical medicine. We have discovered that conditional induction of  the paired-class homeodomain transcription factor mouse Mix-like (mMixl) in differentiating embryonic stem (ES) cells results in acceleration of the entire mesodermal developmental program and in increased numbers of mesodermal, hemangioblastic, and hematopoietic progenitors. Therefore, we hypothesize that mMixl functions early in the recruitment and/or expansion of mesodermal progenitors to the hemangioblastic and hematopoietic lineages and are using genetically manipulated ES cells and mouse models to investigate the earliest events in mesoderm specification. Biochemical approaches and gene expression profiling are being used to study the transcriptional activities and targets of mMixl. These studies may suggest new approaches for cell replacement therapies. Finally, we are using transgenic mouse models to study the development and maturation of cells of the primitive (embryonic) erythroid lineage. An understanding of the various phases of red cell ontogeny will be essential for intelligent approaches to directing erythroid differentiation of stem and progenitor cells for therapeutic purposes and for the efficient production of pure populations of red blood cells for transfusion in severe anemias.

Andrew D. Bergemann, Ph.D.

We are examining the role of cell surface receptors in mediating formation of cell-cell contacts during development. The Eph-related family of receptor tyrosine kinase consists of at least 13 members, several of which display distinctive expression patterns in the developing and adult nervous system. Recent work has focused on Elf 1 and Elf 2, recently-discovered transmembrane ligands for Eph receptors. Elf 1 in developing mouse brain is exposed in the optic tectum. Recently, we have demonstrated matching gradients of Elf 1, in the tectum, and its receptor, MEK 4, in the projecting retinal axons. This result implicates Eif 1 and MEK 4 in development of the topographic retinotectal projection map (1). Elf 2 may play an analogous role in mouse limb development (2). We are examining the effects of various environmental agents, and of microgravity conditions, on the function of these receptors and ligands during development.

James Bieker, Ph.D.

The overall goal of our research is to decipher mechanisms that serve to establish and regulate mammalian erythropoiesis. As a result, differentiating embryonic stem cells in culture are being used as one powerful approach to address these issues in diverse ways: to identify extracellular molecules and illuminate the intracellular pathway they use to play a directive role in erythroid gene expression; to functionally test the cis-acting sequences that control one of these downstream targets known as EKLF, itself a critical erythroid transcription factor; to establish gain-of-function studies that address lineage determination mechanisms during developing and differentiation; and to gain further insight into globin switching mechanisms and identify ways to alter the normal pattern of expression.

Erwin P. Bottinger, M.D.

Millions of Americans are affected with chronic diabetic and non-diabetic kidney diseases that cause kidney failure (end stage renal disease). When kidneys fail, the average life expectancy is just over two years and survival depends on costly and disabling dialysis or transplantation treatments.

State-of-the-art genomics and bioinformatics approaches are used to discover and characterize new molecular targets and pathways associated with apoptosis, transdifferentiation, and fibrogenesis in specialized renal cells exposed to diabetic and other stresses. TGF-beta signaling pathways and targets are a major theme because TGF-beta is a key mediator of these processes.

Model systems used include renal cell culture and mouse models of diabetic and non-diabetic progressive renal disease. A new genomic medicine program aims at identification and validation of molecular biomarkers that predict progressive kidney disease in humans.

Chengleng Cai

We are interested in elucidating the signaling cascades, especially transcriptional signals that regulate mammalian heart development. Understanding the earliest transcriptional signals underlying cardiac induction and development has critical implications for the study of cardiac progenitor/stem cells.

My previous studies have shown that Isl1 (Islet1), a Lim-homeodomain transcription factor, labels a cardiac progenitor population that gives rise to the majority of cardiac segments (right ventricle, outflow formation and atria).  Loss of Isl1 results in a malformed heart that lacks these cardiac segments.  Interestingly, Isl1 expression turns off as cardiac differentiation occurs, suggesting Isl1 can be recognized as a marker for undifferentiated cardiac precursors.

Recently, we identified another cardiac progenitor population- proepicardial/ epicardial cells that are labeled by a T-box transcription factor, Tbx18. With genetic-based lineage tracing, we found that the proepicardium/epicardium can gives rise to multiple cardiac lineages that are distinct from Isl1 progenitors in the mammalian heart. The specific questions addressed in our ongoing studies are:

1. What are upstream and downstream targets of Isl1 in cardiac progenitor cells?
2. What are signals that promote proepicardial/epicardial cell migration and differentiation?
3. Are Tbx18-expressing cardiac progenitor cells isolated from embryonic and adult heart pluripotent for various cardiac lineages in vitro?
4. Can Tbx18/Isl1-expressing cardiac progenitor cells repair injured hearts?

Dennis S. Charney, M.D.

Dr. Charney is one of the nation’s foremost investigators in the neurobiology and treatment of mood and anxiety disorders. He has made fundamental contributions to the understanding of neural circuits, neurochemistry and functional neuroanatomy of the regulation of mood and anxiety and the psychobiological mechanisms of human resilience to stress.

Shu-Hsia Chen, Ph.D.

Malignant metastases present one of the most challenging roadblocks to cancer treatment. In order to develop a treatment modality for metastatic tumors, my lab is focusing on strategies for immune modulated cancer gene therapies. This promising approach has shown up to 100-1000 times higher concentrations of cytokines in situ, attracted dendritic cells (DCs) and inflammatory cells to the tumor site, yet reduced the systemic toxicity mediated by the cytokines. Specifically, my laboratory is pursuing two major directions, immune enhancement and immune tolerance.

Paul Frenette, M.D.

The trafficking of hematopoietic stem cells (HSCs) is critical during development and underlies modern clinical stem cell transplantation. In my laboratory, we are interested in understanding the molecular mechanisms that mediate HSC homing to and egress from their bone marrow niches.  Please consult our recent publications and our laboratory web site (http://www.mssm.edu/labs/frenette/ ) for detailed information.

Bruce Gelb

The Gelb research group is focused on disease gene discovery using positional cloning/candidacy techniques and characterization of the biological roles of such genes in disease pathogenesis. The focus of the laboratory currently is on those traits that are associated with heart malformations. In the past few years, we have identified disease genes for Char and Noonan syndromes. The former is TFAP2B, which encodes a transcription factor of the AP-2 family, and the latter is PTPN11, which include the protein tyrosine phosphatase SHP-2. We are studying the roles of these disease genes in normal developmental and homeostatic processes as well as in disease pathogenesis. We are actively studying additional human genetic traits, both simple and complex, to identify additional disease genes with a particular focus on traits with cardiovascular abnormalities. After recruiting families of adequate size inheriting disorders, we undertake genome-wide scans with polymorphic DNA markers to identify genetic loci through linkage analysis, and then identify disease genes from among known or predicted genes residing in disease loci. The latter relies heavily on bioinformatics, including several software packages that predict genes and protein function. Ongoing biologic studies include site-directed mutagenesis, expression of wild type and mutant proteins in vitro and in eukaryotic cell culture, immunolocalization of proteins, creation of transgenic mice, and phenotyping of mouse models. Through collaborative efforts, we are also studying disease genes in other model organisms such as Drosophila melanogaster and Xenopus laevis.

Isabelle Germano, M.D.

Dr. Germano’s laboratory research focuses on the treatment of malignant gliomas, one of the most challenging issues in neuroscience. Gene therapy strategies currently in clinical trials use viral vectors to deliver therapeutic transgenes directly to normal and tumor cells within the central nervous system. Viral vectors, however, have a number of theoretical and practical limitations. Embryonic stem cells (ES) are totipotent cells with unlimited proliferative capacity, and, unlike other cell types, can be permanently and precisely genetically modified without the use of viral vectors. In collaboration with Dr. Keller, Dr. Germano and her team are currently investigating how these cells can be used as vectors to carry genes into the central nervous system for adjuvant treatment of brain tumors.

Saghi Ghaffari, M.D.- Ph.D.

My laboratory is focused on elucidating signals that regulate blood stem cell formation, differentiation and maturation during their lifetime and mechanisms that control deregulation of these signals in leukemias. It has been recently established definitively that detoxification of reactive oxygen species is required to prevent DNA damage that leads to malignant deadly tumor formation. We have identified that Foxo3 of the FoxO family of Forkhead transcription factors is an essential physiological regulator of normal hematopoietic stem cell behavior. FoxO (Foxo1, Foxo3, Foxo4, Foxo6) transcription factors are mammalian homologs of DAF-16 whose activation in C.elegans promotes the dauer formation and results in a significant increase in worm’s lifespan partly through DAF-16 anti-oxidant function. We found the characteristics of the dauer that is long-lived, resilient and reproductively immature, to resemble in many respects the “quiescent” state of stem cells. Since quiescence is (a) a major characteristic of stem cells, (b) reminiscent of dauer formation and (c) FoxO homolog DAF-16 protects cells from death through its anti-oxidant function, we postulated that FoxO transcription factors may protect mammalian stem cells from oxidative stress. We demonstrated that Foxo3 regulation of oxidative stress in hematopoietic stem cells is essential for maintenance of hematopoietic stem cell pool and have identified several putative downstream targets of Foxo3 in hematopoietic stem cells. Using, genetic, biochemical and molecular approaches we are investigating how Foxo3 function is controlled in adult and embryonic hematopoietic stem cells (and in human undifferentiated embryonic stem cells), which genes are controlled by Foxo3 in these cells and what is the source of oxidative stress in stem cells. We believe we will learn critical information regarding the mechanisms of stem cell leukemic transformation in this process.

George W. Huntley, Ph.D.

The use of neural stem cells holds great promise for repairing neural circuits damaged by injury or disease. Successful repair requires an understanding of how growing axons recognize their correct target neurons. This is important because the consequences of inappropriate axon-targeting can be severe and maladaptive. Dr. Huntley’s laboratory studies molecular mechanisms of synaptic circuit formation, targeting and plasticity. Current focus is on the role of the cadherin family of cell adhesion molecules and extracellular proteases in orchestrating connection formation during development and in forms of synaptic plasticity thought to underlie learning and memory, and in enabling maladaptive intraspinal sprouting of nocieptive primary afferent sensory axons in models of neuropathic pain.

Luis Isola, M.D.

As leader of the Bone Marrow Transplantation (BMT) service at Mount Sinai, Dr. Isola promotes clinical and translational research on bone marrow transplantation. He has developed several protocols including non-ablative conditioning for allogeneic transplantation, the use of immunomagnetic technology for stem cell selection in haplo-mismatched transplantation and a combination of these two approaches for unrelated transplantation in older adults. Under his leadership the Mount Sinai BMT service performed the first mismatched transplantation using non-ablative conditioning. It is also one of only a few in the country with a FDA-approved protocol for haplo-mismatched transplantation. This is particularly important for minority populations as it is exceedingly difficult to find matched unrelated donors for patients from minorities. Also under his leadership, Mount Sinai was one of the first centers in the country to offer volunteer, unrelated peripheral blood stem cell collections for allotransplantation under the auspices of the National Marrow Donor Program. Dr. Isola has also been at the forefront in developing computerized systems for data management, capabilities that are crucial for maintaining accreditation by many organizations.

Kevin A. Kelley, Ph.D.

The Mouse Genetics Shared Research Facility (SRF) was established in 1999 to provide the faculty of Mount Sinai with a state-of-the-art facility for the production of novel, genetically manipulated mouse lines. The research efforts of this group include microinjection of gene fragments for production of transgenic mice, microinjection of selected ES cells for the production of gene-targeted mouse lines, rederivations of mouse lines for removal of mouse pathogens, and cryopreservation of mouse gametes. In addition to these research goals, the SRF provides investigators with an outstanding resource for aid with transgene design, protocols for ES cell culture, and general assistance with all phases of mouse genetics. In addition to the goals of the SRF, my collaborative research interests using the mouse as a model system span several areas of developmental biology as evidenced by the following publications.

Robert Krauss, Ph.D.

Our primary interest is in mechanisms by which signal transduction pathways regulate pattern formation and cell differentiation during development, and how such processes may go awry in disease. Much of our work focuses on multifunctional cell surface receptors of the immunoglobulin superfamily, including Cdo, Boc and neogenin. Cdo and Boc function in the Sonic hedgehog (Shh) pathway to regulate formation of the midline in the CNS and face, and mice lacking Cdo display holoprosencephaly, a common and devastating developmental anomaly associated with defects in Shh signaling in humans. Both Cdo and Boc bind directly to Shh and may serve as co-receptors for Hedgehog proteins. Cdo and Boc also interact with neogenin and with the cell-cell adhesion molecule N-cadherin in muscle precursor cells, including satellite cells, the resident adult stem cells of the skeletal muscle lineage. In these cells, Cdo stimulates signaling via the p38 MAP kinase pathway to promote cell differentiation. Both Shh and N-cadherin are implicated in regulation of stem cell niche and fate, and we are interested in whether the activities of these factors are coordinated by Cdo/Boc, which are able to interact with both of them.

John (Xiajun) Li, Ph.D.

Epigenetic regulation is essential for mammalian embryonic development. Reprogramming of genomic imprints in the germline and subsequent reconstitution of asymmetric expression of imprinted genes following fertilization are necessary for the embryos to develop properly. Consistent with this, a vast majority of cloned embryos die in utero due to the defects in epigenetic reprogramming, mainly the failure to re-establish proper genomic imprints. ES cells derived from therapeutic cloning-based approaches also have the defects in reprogramming of genomic imprints. Therefore, it is important to know how to possibly tamper with the genomic imprinting machinery in the ES cells created by nuclear transfer so that proper development of different lineages of cells can be achieved for therapeutic applications.

Germline-derived differential methylated regions (DMR) at the imprinting control centers are involved in the maintenance, possibly in the establishment as well, of genomic imprints. DNA methylation genomic imprints are reprogrammed in the germline and are protected from genome-wide demethylation process in early pre-implantation embryos. Many progresses have made toward understanding the functions of DNA methyltransferases in the establishment and maintenance of DNA methylation imprints.

However, many outstanding questions still remain: How are DNA methyltransferases targeted to specific imprinted regions to establish DNA methylation imprints? How are these heritable methylation imprints maintained and re-established if ever lost? Indeed, our recent finding suggest that these germline-derived DNA methylation imprints can be lost in early pre-implantation embryos and they can be re-acquired after implantation. These unexpected results suggest that it might be possible to manipulate DNA methylation genomic imprints in vitro. It also raises the hope that genomic imprinting defects present in the cloned embryos and ES cells derived from therapeutic cloning may be amended. We are currently using mouse ES cells as a model system to analyze the maintenance of genomic imprints in vitro.

Riegh-Yi Lin, Ph.D.
The main interest of our laboratory is to study the role of the TSH (thyroid stimulating hormone) signaling pathway in thyroid development and disease. TSH and its receptor TSHR are key regulators of thyroid cell functions during embryogenesis and in the adult.  TSH resistance is one of the causes of congenital hypothyroidism – the most common inborn endocrine disorder. One in every 3500 newborns is affected by the condition, which is due primarily to developmental defects leading to an absent, ectopic or hypoplastic thyroid gland. There are two areas of research in our laboratory. One part of the laboratory studies how the pluripotent embryonic stem cells respond to external signals to give rise to thyrocytes. The second area of research in the laboratory is the characterization of the early events involved in the establishment and maturation of embryonic thyroid gland. We utilize a broad range of techniques encompassing cell, molecular and developmental biology. We also employ transgenic and knockout technologies in mice. In addition, our studies may pave the way for the use of human embryonic stem cells as a model system to study thyroid development, and potentially the role of abnormal cell development in the genesis of thyroid disease.

Kateri Moore, Ph.D.

There is a cellular milieu that surrounds and supports the blood forming or hematopoietic stem cell.  Throughout adult life these stem cells are present within the bone marrow and are thought to be located in apposition to the endosteal surface of the bone.  Stromal cellular elements provide a unique microenvironmental space or niche that mediates the extrinsic molecular signals involved in the balance of self-renewal and commitment decisions of stem cells. My work is focused on defining the most primitive stem cell microenvironmental niche at the cellular and molecular level. Our previous studies have shown that a cell line, AFT024, can maintain competitive repopulating stem cell activity that is qualitatively and quantitatively identical to that present in freshly purified cells. We suggest that the AFT024 stromal cell line provides a unique and positively acting molecular milieu that maintains self-renewing stem cells. To isolate the components of this milieu we have constructed a subtracted cDNA library enriched for molecules preferentially expressed in this supporting line. We have assembled a biological process oriented Web-based interface, the Stromal Cell Database (StroCDB). Candidate genes from this database are being tested in gain and loss of function studies and are being used to develop mouse models. These genetically modified mice provide model systems to both manipulate and visualize stem cells and their niches in vivo under normal homeostasis and/or after systemic and/or specific microenvironmental perturbation.  In addition, we are investigating the “molecular cross-talk” that occurs when stem cells and stromal cells interact under a variety of conditions. This research will provide invaluable insights into the intrinsic and extrinsic mechanisms that balance the self-renewal and differentiation of hematopoietic stem cells and perhaps of all stem cells.

Takeshi Sakurai, Ph.D.

Our nervous system is made of a number of highly diverse cell types that are derived from one type of cells, neuronal stem cells. These highly diverse cell types interact with each other to support development and function of the nervous system. We have been characterizing molecules involved in cell-cell interactions in the nervous system, specifically neuronal cell adhesion molecules, which play critical roles in development and function of the nervous system. Dysfunction of these molecules may lead to developmental alterations in the brain, resulting in functional changes that lead to neurological and/or psychiatric disorders. 

Recent studies suggest that alterations in molecular processes involved in oligodendrocyte development and differentiation leading to dysfunction of oligodendrocytes, result in disconnectivity between certain brain regions and some of the clinical features of schizophrenia.  Therefore, schizophrenia can be considered as a disorder caused in part by alterations in the differentiation and maturation processes of neuronal stem cells and/or oligodendrocyte precursor cells. 

Our research effort has been to characterize the function of selected molecules, which have been identified to be associated with schizophrenia through genetic and gene expression studies using postmortem brains, in development and differentiation of diverse cell types from neuronal stem cells.  These studies involve both in vitro culture systems and animal models.  Our primary focus has been on cell adhesion and associated molecules that are expressed in stem cells and/or oligodendrocyte precursor cells that may be involved in differentiation of these cells. 

Our research goal is to identify pathways and molecules that are affected in stem cells and/or oligodendrocyte precursor cells and to devise therapeutic approaches targeting these pathways and molecules to ameliorate deficits in oligodendrocyte development as a means of reducing the symptoms of schizophrenia and possibly other dysmyelinating  disorders.

Hans Snoeck, M.D.- Ph.D.

A tight balance between the self-renewal of hematopoietic stem cells (HSC) and their differentiation into specific blood cell lineages is critical for the production of normal numbers of blood cells throughout our life span. Defining the signaling pathways and transcriptional machinery regulating these events is essential to understand the control of lineage commitment within the hematopoietic system and ultimately to enable the manipulation of these decisions in HSC both in culture and in vivo. My laboratory has focused on the analysis of quantitative genetic variation in the hematopoietic stem cell compartment of the mouse to define regulatory pathways that are relevant in vivo. Using this strategy, we have identified transforming growth factor-beta2 (TGF-b2) as a positive regulator of the cycling activity of HSC. Furthermore, this approach allows us to analyze the organismal consequences of genetic variation in the stem cell kinetics. These include the lethality of cytotoxic agents and the progression of age-related changes in the hematopoietic system, in particular in T cell development.

Sergei Y. Sokol, Ph.D.

The central nervous system forms in vertebrate embryos as a result of inductive interactions between competent ectoderm and a special dorsal signaling center, known in amphibians as the Spemann organizer. Complex interactions between the products encoded by these genes result in the differentiation of neurons and glial cells, organized in a specific mediolateral and anteroposterior pattern. Several signaling pathways, triggered by bone morphogenetic proteins, fibroblast growth factors and Wnt proteins were implicated in early neural development in vertebrates.

In Drosophila neuroblasts, cell fates are regulated by asymmetric distribution of molecular determinants and the direction of the mitotic spindle. In vertebrate embryos and mammalian cells the significance of asymmetric division and spindle orientation for cell type specification is less well studied. We would like to understand the role for mitotic spindle orientation and asymmetric cell division of NPCs in neuronal cell fate determination.

Our studies demonstrate that Lgl is required for cell polarity and asymmetric cell division during primary neurogenesis in Xenopus ectoderm, and its localization may be controlled by Wnt signaling (Dollar et al., 2005, and not shown). As neural stem cells may undergo similar asymmetric divisions, we hypothesize that the role of Lgl as an essential regulator of neuronal differentiation is preserved in these cells. We study the subcellular localization of Lgl and Par proteins in cells undergoing neural differentiation and assess how modulation of their levels or localization would influence neural tissue differentiation. The knowledge of molecular mechanisms regulating neuronal differentiation should have implications on stem cell research and regenerative medicine.

Additionally, our studies show that Frodo, a new signaling protein, is required for the specification of neural tissue. Frodo is a founding member of a family of related proteins that operate in multiple signaling pathways (Brott and Sokol, 2005). Using antisense morpholino oligonucleotides (MO), an efficient in vivo method of inactivating gene products, we have demonstrated an essential role for Frodo in neural development (Hikasa and Sokol, 2004). As Frodo is a component of the Wnt signaling pathway, we use transgenic mice and frog embryos to investigate a role for Wnt signaling in asymmetric cell divisions during neurogenesis.

David Sternberg

The overall goals of this research program are 1) to define the molecular pathways that underlie cancers derived from blood forming tissues and 2) to develop new interventions to disrupt these pathways in hematologic cancers. The principal focus concerns lymphomas that arise due to inappropriate expression and activation of the ALK tyrosine kinase. This protein is fused to a variety of partners as a result of chromosomal translocations in lymphoma, and animal models clearly demonstrate that ALK fusion kinases are causally involved in the emergence of these malignancies. The ALK enzyme and downstream signaling intermediates will therefore serve as useful targets for the design of novel therapeutic strategies.

We have identified several pathways that regulate survival and proliferative signaling by the NPM-ALK tyrosine kinase of anaplastic large cell lymphoma (ALCL). We have shown that the FOXO3a transcription factor is phosphorylated in response to NPM-ALK expression, and this causes the relocalization of FOXO3a from the nucleus to the cytoplasm. By this means, NPM-ALK overcomes a barrier to cell proliferation and survival imposed by FOXO3a. Moreover, we have identified the MEK/ERK and mTOR/S6K signaling modules as critical regulators of cell proliferation triggered by NPM-ALK expression. These findings and those of other studies are validated in this lab through the use of a murine retroviral bone marrow transplant model of hematopoietic neoplasia.

 

Reshma Taneja, Ph.D.

Skeletal muscle exhibits a tremendous capacity for regeneration in response to muscle injury induced by disease, trauma, or intensive exercise. Satellite cells, the local skeletal muscle stem cells are primarily responsible for muscle regeneration. Thus, a failure of myogenic satellite cells to maintain muscle regeneration is the underlying basis of muscular dystrophies. A long-term interest of my laboratory is to understand the role of basic helix-loop-helix family of transcription factors in orchestrating skeletal muscle differentiation and regeneration. Our recent studies demonstrate that the bHLH factor Stra13 plays a critical role in skeletal muscle regeneration. Stra13 knockout mice exhibit defective regeneration and fibrosis in response to injury along with an increase in Notch activity. Using mouse genetics as well as molecular and biochemical techniques, our goal is to define the signaling pathways and molecular mechanisms by which bHL proteins function in myogenic differentiation and skeletal muscle repair, and whether their deregulated expression is associated with muscular dystrophies.

Daniel Weinstein, Ph.D.

All tissues in the animal derive from the three primary germ layers: ectoderm endoderm, and mesoderm. Endoderm derivatives contribute to the organs of the gut, while ectodermal derivatives form the epidermis and central nervous system. The mesodermal germ layer plays a pivot role in organizing the vertebrate body axes, and itself gives rise to the muscular, skeletal, and circulatory systems. My laboratory’s effort focuses on elucidating the mechanisms underlying germ layer formation and patterning in the frog, xenopus laevis. Our present studies are concerned primarily with the mechanisms that restrict inappropriate mesoderm and endoderm formation during early development. Recent work in our lab suggests that several members of the Fox family of transcription factors function as mesendodermal antagonists during Xenopus gastrulation. Work in the laboratory is focused on characterizing the mechanisms underlying Fox mediated germ layer suppression, using a combination of molecular, biochemical, and embryological approaches.

Patricia D. Wilson, Ph.D.

The mouse ES/EB system is used to specify mesodermal lineages and to derive specific renal epithelial progenitors by optimization of tissue culture, activin incubation and FACS sorting conditions. To date, this has enabled the isolation and enrichment of proximal tubule and collecting duct progenitor populations as assessed by RT-PCR marker analysis in vitro. Lineage tracing and double immunofluorescence after injection into fetal kidneys in organ culture as well as newborn mouse kidneys in vivo is used to assess functional incorporation into mesenchymally-derived proximal tubule and ureteric bud-derived collecting tubular epithelia respectively. Studies are underway to purify these cell populations; assess their full differentiation potential in vitro and in vivo and to test their efficiacy to repair and restore function to mouse models of renal injury, that left untreated lead to renal failure.

Jose Wolosin, Ph.D.

My laboratory has a long-standing interest in the biology of the limbal/corneal epithelium. Limbal damage from various etiologies causing the irreversible stem cell loss results in the functional failure of the stem cell-free epithelium overlying and protecting the critical corneal domain. The ensuing scarring and neovascularization of the otherwise transparent cornea leads to severe loss in visual acuity including complete blindness. To develop the basic cellular knowledge needed to advance ocular reconstructive procedures, we have recently isolated the limbal stem cell and are studying its molecular make-up, and functional characteristics. Cell culture studies seek to identify condition for maximal replication of this cell with preservation of undifferentiated properties. Microarray studies are currently being pursued to determine its gene expression patterns.

Savio Woo, Ph.D.

An application of the genome-targeted transgene delivery system is in murine and human embryonic stem cells. Differentiation-specifying genes expressed under inducible promoters might be delivered to the ES cells that will direct their development into specific tissue cell types at the appropriate time frame, and immune-modulating genes under tissue specific promoters might be delivered to abrogate immune responses in allogeneic hosts against the transplanted grafts that were derived from ES cells. Active collaborative research studies are being conducted with Drs. Gordon Keller and Jonathan Bromberg in the Black Family Stem Cell Institute.