Parathyroid oxyphil cells (green) within a parathyroid adenoma
In collaboration with Dr. Julie Sosa, the Endocrine Neoplasia Laboratory employs a combination of molecular, murine modeling, and live-cell imaging approaches to examine the underlying mechanisms of disrupted calcium sensing in parathyroid tumors. Our group has shown recently that parathyroid adenomas are comprised of functionally discrete and separable cellular subpopulations that respond differentially to extracellular calcium stimulation and that arise in many cases following polyclonal expansion of progenitor cells within the parathyroid gland.
To examine cell-signaling behaviors in the native context of viable tumor tissue, we have developed a novel ex vivo imaging system that enables direct provocative testing of tumor reactivity to physiological agonist engagement at single-cell resolution. These methods form the foundation for our laboratory’s ongoing efforts to understand how perturbed biochemical signaling can contribute to the development of preneoplastic lesions in human endocrine neoplasia.
- Ex vivo analysis of biochemical signaling in human parathyroid tissue
- High-throughput image-based quantitative metrics of live cell signaling
Development of live-cell microfluidic imaging platforms for functional interrogation of tumor cell behaviors
- Molecular determinants of calcium sensing deficiency in parathyroid disease
Isolation of distinct cellular subtypes from a parathyroid adenoma. Background image=immunofluorescence. Foreground image=flow cytometry sorting of tumor cells. Inset=electron microscope images of parathyroid tumor cell types isolated by flow cytometry
Our group has developed a series of novel image-based approaches for visualizing the functional consequences of intratumoral heterogeneity within living human tumor specimens. We have shown recently that human parathyroid tumors are comprised of functionally discrete and separable cellular subpopulations that respond differentially to extracellular calcium stimulation and that arise in many cases following polyclonal expansion of progenitor cells within the parathyroid gland. We are employing a combination of live single-cell dynamic calcium response imaging at both the single-cell and intact tissue level, in combination with transgenic mouse modeling to study how these newly identified cellular subpopulations drive the failure of appropriate calcium sensing in parathyroid disease.
Dr. Julie Sosa and I are MPIs on an active R21 proposal that utilizes a novel live-cell microraft system that we developed to investigate the molecular determinants of parathyroid cell calcium responsiveness at the single-cell level.
Overlay of live-cell calcium responsiveness
readout (green) and parathyroid hormone
expression (red) in a living human
parathyroid tumor section
In addition, our group has developed immunofluorescence-based and flow cytometric approaches for studying signaling events, cellular proliferation, and oncoprotein-mediated transformation in addition to extensive prior work on transcriptional regulation and promoter occupancy. Our laboratory is currently partnering with Cell Microsystems, Inc., in the development of a high-performance optical imaging device for stand-alone live-cell imaging at subcellular resolution.
In collaboration with Dr. John Olson of the University of Maryland, we have shown that aberrant overexpression of a potent regulator of G-protein signaling is a mechanism for inhibiting cellular responsiveness to calcium sensing both in vitro and in vivo in RGS5-deficient mice, and we recently completed an R01 project dedicated to elucidating the role of this regulator (RGS5) in parathyroid disease in a novel transgenic mouse model. As part of this work, we generated a new transgenic strain engineered for conditional, tissue-specific expression of RGS5 in the parathyroid gland.
Please feel free to contact the laboratory or come by for a visit:
James Koh, PhD
Office: Room B217 LSRC
Laboratory: Room B215 LSRC