Instructor, Medicine - Gastroenterology & Hepatology
Board Certification: Gastroenterology, American Board of Internal Medicine (2014)
Fellowship:Stanford Hospital and Clinics (2010) CA
Residency:Stanford Hospital and Clinics (2010) CA
Internship:Stanford Hospital and Clinics (2009) CA
Medical Education:University of Chicago Pritzker School of Medicine (2008)
Board Certification: Internal Medicine, American Board of Internal Medicine (2012)
Doctor of Philosophy, The Rockefeller University (2007)
Bachelor of Science, Northwestern University (1999)
Identification and genetic manipulation of human and mouse oesophageal stem cells.
2016; 65 (7): 1077-1086
Human oesophageal stem cell research is hampered by the lack of an optimal assay system to study self-renewal and differentiation. We aimed to identify and characterise human and mouse oesophageal stem/progenitor cells by establishing 3-dimensional organotypic sphere culture systems for both species.Primary oesophageal epithelial cells were freshly isolated and fluorescence-activated cell sorting (FACS)-sorted from human and mouse oesophagus and 3-dimensional organotypic sphere culture systems were developed. The self-renewing potential and differentiation status of novel subpopulations were assessed by sphere-forming ability, cell cycle analysis, immunostaining, qPCR and RNA-Seq.Primary human and mouse oesophageal epithelial cells clonally formed esophagospheres consisting of stratified squamous epithelium. Sphere-forming cells could self-renew and form esophagospheres for over 43 passages in vitro and generated stratified squamous epithelium when transplanted under the kidney capsule of immunodeficient mice. Sphere-forming cells were 10-15-fold enriched among human CD49f(hi)CD24(low) cells and murine CD49f(+)CD24(low)CD71(low) cells compared with the most differentiated cells. Genetic elimination of p63 in mouse and human oesophageal cells dramatically decreased esophagosphere formation and basal gene expression while increasing suprabasal gene expression.We developed clonogenic and organotypic culture systems for the quantitative analyses of human and mouse oesophageal stem/progenitor cells and identified novel cell surface marker combinations that enrich for these cells. Using this system, we demonstrate that elimination of p63 inhibits self-renewal of human oesophageal stem/progenitor cells. We anticipate that these esophagosphere culture systems will facilitate studies of oesophageal stem cell biology and may prove useful for ex vivo expansion of human oesophageal stem cells.
View details for DOI 10.1136/gutjnl-2014-308491
View details for PubMedID 25897018
- Identification and genetic manipulation of human and mouse oesophageal stem cells GUT 2016; 65 (7): 1077-1086
- Adult Intestinal Malrotation: When Things Turn the Wrong Way DIGESTIVE DISEASES AND SCIENCES 2012; 57 (2): 284-287
Lhx2 maintains stem cell character in hair follicles
2006; 312 (5782): 1946-1949
During embryogenesis, stem cells are set aside to fuel the postnatal hair cycle and repair the epidermis after injury. To define how hair follicle stem cells are specified and maintained in an undifferentiated state, we developed a strategy to isolate and transcriptionally profile embryonic hair progenitors in mice. We identified Lhx2 as a transcription factor positioned downstream of signals necessary to specify hair follicle stem cells, but upstream from signals required to drive activated stem cells to terminally differentiate. Using gain- and loss-of-function studies, we uncovered a role for Lhx2 in maintaining the growth and undifferentiated properties of hair follicle progenitors.
View details for DOI 10.1126/science.1128004
View details for Web of Science ID 000238848100058
View details for PubMedID 16809539
A developmental conundrum: a stabilized form of beta-catenin lacking the transcriptional activation domain triggers features of hair cell fate in epidermal cells and epidermal cell fate in hair follicle cells
JOURNAL OF CELL BIOLOGY
2002; 158 (2): 331-344
Wnt signaling orchestrates morphogenetic processes in which changes in gene expression are associated with dramatic changes in cell organization within developing tissue/organs. Upon signaling, excess beta-catenin not utilized at cell-cell junctions becomes stabilized, where it can provide the transcriptional activating domain for Lef/Tcf DNA binding proteins. In skin epithelium, forced stabilization of beta-catenin in epidermis promotes hair follicle morphogenesis, whereas conditional removal of beta-catenin in hair progenitor cells specifies an epidermal fate. We now report that a single protein, a stabilized version of beta-catenin lacking the COOH-terminal transactivation domain, acts in epidermis to promote hair fates and in hair cells to promote epidermal fate. This reveals fundamental differences in ways that epidermal and hair cells naturally respond to beta-catenin signaling. In exploring the phenotype, we uncovered mechanistic insights into the complexities of Lef1/Tcf/beta-catenin signaling. Importantly, how a cell will respond to the transgene product, where it will be localized, and whether it can lead to activation of endogenous beta-catenin/Tcf/Lef complexes is specifically tailored to skin stem cells, their particular lineage and their relative stage of differentiation. Finally, by varying the level of beta-catenin signaling during a cell fate program, the skin cell appears to be pliable, switching fates multiple times.
View details for DOI 10.1083/jcb.200204134
View details for Web of Science ID 000177106200015
View details for PubMedID 12135986