Hematopoiesis in Health and Disease

Hematopoietic stem cells and disease modeling

The central focus of this independent research program is:

  1. To model hematopoietic disorders employing disease-in-a-dish approach utilizing patient derived and gene-edited (CRIPSR/Cas9) isogenic induced pluripotent stem cells (iPSCs)
  2. To decipher the epigenetic landscape and transcriptomic program controlling hematopoietic stem cells functions and transformation to hematologic malignancies.

Modeling hematopoietic disorder using iPSCs

This laboratory focuses on modeling hematopoietic disorders using patient derived and gene-edited (CRISPR/Cas9) induced pluripotent stem cells (iPSCs). Our aim is to unravel the mechanisms of G-CSF resistance in ELANE mutant Severe Congenital Neutropenia (SCN), and progression to secondary myelodysplastic syndrome and acute myeloid leukemia (MDS/AML). Chronic administration of G-CSF ameliorates neutropenia and decrease life threatening bacterial and fungal infections in SCN patients. However, G-CSF sensitivity varies significantly between patients and some ELANE mutant patients do not respond to G-CSF at all. SCN patients requiring higher G-CSF with lower ANC recovery are prone to adverse infections and secondary MDS and AML development.

Using iPSC-based disease modeling approach, we deciphered the pathobiology of severe congenital neutropenia (SCN) with heterozygous dominant mutations (NEQ97P, NEI118N) in ELANE, gene encoding neutrophil elastage (NE). The mechanisms of SCN with mutations (p.Q97>P and P.I118>N) in exon-3 of ELANE pivot around accumulation of mutant NE in endoplasmic reticulum (ER), induction of unfolded protein response (UPR) and ER stress pathway, and cell death and differentiation arrest at promyelocyte and myelocytes stages of neutrophil maturation. Sivelestat, a small molecule inhibitor of NE sensitizes the cells to G-CSF and ameliorates UPR/ER-stress and rescues granulopoiesis by upregulating CEBPA. This study is highly significant as it for the first time demonstrates the disease pathogenesis in physiologically relevant cells (Nayak et al., JCI. 2015. PMID:26193632). In another study, using isogenic and gene edited (CRIPSR/Cas9) iPSCs, we modeled ELANE translation initiation codon mutant (ATG to GTG, NEM1V) SCN pathobiology and unraveled mechanisms of G-CSF (granulocyte colony stimulating factor) resistance (Tidwell et al., Blood, 2014.  PMID:  24184683   These studies are very significant as nearly 25% of patients on high-dose GCSF therapy evolve to myelodysplastic syndrome (MDS) and acute myeloid leukemia (AML).

Modeling hematopoietic disorder using iPSCs diagram

This laboratory also studies hematopoietic cell regeneration from healthy donor (HD) human iPSCs, and analyze their functions in vivo in murine model to generate proof-of-concept for large scale hematopoietic cells production for transfusion (Trump et al., Stem Cell Transl Med, 2019. DOI: 10.1002/sctm.18-0255).

Epigenetic regulation of Hematopoietic stem cells and transformation to hematologic malignancies

This laboratory also focuses on deciphering the epigenetic landscape and transcriptomic program controlling hematopoietic stem cells functions and transformation to hematologic malignancies. 

Epigenetic regulation of LIC in B-ALL diagram

We use transgenic murine model (knock-in and inducible knock-out) and lentiviral expression system to unravel molecular mechanisms of the initiation and/or propagation of B-cell acute lymphoblastic leukemia (B-ALL). Of the 22 recently defined B-ALL subtypes, Ph+ and Ph-like ALL continue to represent the highest risk and most resistant pediatric ALL with increased incidence of minimal residual disease (MRD) and relapse. B-ALL resistance is attributed to the epigenetic reprogramming and acquisition of stem cell like properties with increased self-renewal and differentiation arrest. However, our understanding of the mechanisms controlling epigenetic landscape, loss of heterozygosity of secondary tumor suppression transformation mutations, reprograming of transformed B-cell progenitors, B-ALL progression and maintenance of leukemic initiating cells (LIC) remains poor. In our recent studies we identified the connection between the oncogene induced cellular signaling and epigenetic regulation in B-ALL progression (Nayak et al., Nat Comm, 2019.   PMID: 30610188; Nayak et al. Nat Comm, 2022. PMID:35650206  In a collaborative project, using state-of-art methodologies, we deciphered the retinoic acid receptor (RXRa and RXRb) mediated epigenetic regulation of HSC quiescence and steady state hematopoiesis (Menéndez-Gutiérrez et al., Blood, 2023, PMID: 36347014).

Research Team

Ramesh C. Nayak, PhD
Assistant Professor
Email: Ramesh.Nayak@uc.edu
Phone:  513-415-9604

Shakyrah Smith, BS
Research assistant