Postdoctoral Scholars of the Siebel Stem Cell Institute

Siebel Postdocs

Wei Guo

Hedgehog (Hh) signaling is critically important in regulating vertebrate organogenesis. Conserved roles as a morphogen and in tissue homeostasis make Hh signaling fundamental to most forms of metazoan life. I am interested in understanding the mechanisms by which heparan sulfate proteoglycans (HSPG) regulate Hh distribution and gradient formation by generating HSPG biogenesis deficient mouse ES cells and assaying Hh surface distribution in neuralized embryoid bodies derived from mES cell. This allows us to better understand on how Shh gradients influence organogenesis and help correctly shape Shh gradients in vitro to optimize differentiation of organoids or the enrichment of desired cell types.

Jeremy Henderson
Mesenchymal stem cell (MSC)-based therapies rely on secreted particles like bioactive extracellular vesicles (EVs) to initiate desired outcomes at engraftment sites. Nucleic acids packaged in EVs, particularly small non-coding RNAs, are well-documented contributors to this mode of communication. My research aims to provide a biochemical description for the selective packaging of nucleic acid material into MSC-EVs. This groundwork will enable the potential to bioengineer EVs with altered nucleic acid profiles. This work also aims to contribute to a more general understanding of cellular communication paradigms through EV packaging of nucleic acids, and its importance for RNA homeostasis during MSC differentiation.

Won-Tae Kim
Telomeres are repetitive DNA sequences that protect the natural chromosome ends. Abnormal telomere maintenance plays a role in bone marrow failure syndrome (BMFS) and stem cell depletion. In addition, telomere shortening and telomerase mutations are known risk factors for hematologic cancers. I’m working to better understand how telomeres regulate blood cell development and cancer generation by genome editing of human hematopoietic stem cells. The goal of our study is to be able to detect patients that are at risk of hematologic cancers due to telomere dysfunction.

Johannes Schöneberg
I work at the exciting interface between stem cells, data science and advanced imaging. Together with the Drubin, Hockemeyer and Betzig labs, I differentiate stem cells into 3D organoids of brain and intestinal tissue, image them with the lattice light-sheet microscope and develop algorithms to segment the data.

Rocío Sampayo
Differentiation or self-renewal of adult neural stem cells (NSCs) within the hippocampus has a major impact in the regulation of memory and learning. Dr. Schaffer's lab has recently shown that NSCs are sensitive to mechanical stimuli from the extracellular matrix (ECM) during a short temporal window of 12-36 hours that determines their fate days or even weeks later. My aim is to use a tunable stiffness matrix together with optogenetic tools to unravel the mechanism responsible for this "mechanical memory". In particular, my research will be focused in the study of the role of small GTPases of the Rho subfamily, RhoA and Cdc42, which have been described to participate in mechanotransduction in NSC. Future applications of this knowledge include new therapies such as functionalized biomaterials with the potential to replace damaged brain tissues or interventions to target RhoA/Cdc42 pathways to control NSC differentiation.