J Cook

Overview:

I am interested in all aspects of flow cytometric analysis and cell sorting, especially the application of these techniques to elucidation of the development of the immune system and understanding primary immunodeficiencies. I am committed to assisting the Duke research community in the maximum utilization of the cytometers and techniques available to them through our shared reasource, including training of individuals to perform their own cytometry. My goal is to insure that their flow cytometry experiments will lead to peer reviewed publications and strong fundable RO1 applications.

Positions:

Assistant Research Professor of Immunology

Immunology
School of Medicine

Member of the Duke Cancer Institute

Duke Cancer Institute
School of Medicine

Education:

Ph.D. 1984

University of Virginia

Publications:

Amino acids stimulate cholecystokinin release through the Ca2+-sensing receptor.

Cholecystokinin (CCK) is produced by discrete endocrine cells in the proximal small intestine and is released following the ingestion of food. CCK is the primary hormone responsible for gallbladder contraction and has potent effects on pancreatic secretion, gastric emptying, and satiety. In addition to fats, digested proteins and aromatic amino acids are major stimulants of CCK release. However, the cellular mechanism by which amino acids affect CCK secretion is unknown. The Ca(2+)-sensing receptor (CaSR) that was originally identified on parathyroid cells is not only sensitive to extracellular Ca(2+) but is activated by extracellular aromatic amino acids. It has been postulated that this receptor may be involved in gastrointestinal hormone secretion. Using transgenic mice expressing a CCK promoter driven/enhanced green fluorescent protein (GFP) transgene, we have been able to identify and purify viable intestinal CCK cells. Intestinal mucosal CCK cells were enriched >200-fold by fluorescence-activated cell sorting. These cells were then used for real-time PCR identification of CaSR. Immunohistochemical staining with an antibody specific for CaSR confirmed colocalization of CaSR to CCK cells. In isolated CCK cells loaded with a Ca(2+)-sensitive dye, the amino acids phenylalanine and tryptophan, but not nonaromatic amino acids, caused an increase in intracellular Ca(2+) ([Ca(2+)](i)). The increase in [Ca(2+)](i) was blocked by the CaSR inhibitor Calhex 231. Phenylalanine and tryptophan stimulated CCK release from intestinal CCK cells, and this stimulation was also blocked by CaSR inhibition. Electrophysiological recordings from isolated CCK-GFP cells revealed these cells to possess a predominant outwardly rectifying potassium current. Administration of phenylalanine inhibited basal K(+) channel activity and caused CCK cell depolarization, consistent with changes necessary for hormone secretion. These findings indicate that amino acids have a direct effect on CCK cells to stimulate CCK release by activating CaSR and suggest that CaSR is the physiological mechanism through which amino acids regulate CCK secretion.
Authors
Wang, Y; Chandra, R; Samsa, LA; Gooch, B; Fee, BE; Cook, JM; Vigna, SR; Grant, AO; Liddle, RA
MLA Citation
Wang, Yu, et al. “Amino acids stimulate cholecystokinin release through the Ca2+-sensing receptor..” Am J Physiol Gastrointest Liver Physiol, vol. 300, no. 4, Apr. 2011, pp. G528–37. Pubmed, doi:10.1152/ajpgi.00387.2010.
URI
https://scholars.duke.edu/individual/pub774327
PMID
21183662
Source
pubmed
Published In
Am J Physiol Gastrointest Liver Physiol
Volume
300
Published Date
Start Page
G528
End Page
G537
DOI
10.1152/ajpgi.00387.2010

Plasmonic flow cytometry by immunolabeled nanorods.

Fluorescence-based flow cytometry measures multiple cellular characteristics, including levels of receptor expression, by assessing the fluorescence intensity from a population of cells whose cell surface receptors are bound by a fluorescently labeled antibody or ligand for that receptor. Functionalized noble metal nanoparticles provide a complementary method of receptor labeling based on plasmonics for population analysis by flow cytometry. The potential benefits of using plasmonic nanoparticles to label cell surface receptors in flow cytometry include scattering intensity from a single particle that is equivalent to fluorescence intensity of 10⁵ fluorescein molecules, biocompatibility and low cytotoxicity, and nonquenching optical properties. The large spectral tunability of nanorods also provides convenient access to plasmonic markers with peak surface plasmon resonances ranging from 600 to 2,200 nm, unlike gold nanosphere markers that are limited to visible wavelengths. Gold nanorod-based plasmonic flow cytometry is demonstrated herein by comparing the scattering of cells bound to anti-epidermal growth factor receptor (EGFR)-conjugated nanorods to the emission of cells bound to anti-EGFR-conjugated fluorescent labels. EGFR-expressing cells exhibited a statistically significant six-fold increase in scattering when labeled with anti-EGFR-conjugated nanorods compared with labeling with IgG1-conjugated nanorods. Large scattering intensities were observed despite using a 1,000-fold lower concentration of nanorod-conjugated antibody relative to the fluorescently labeled antibody.
Authors
Crow, MJ; Marinakos, SM; Cook, JM; Chilkoti, A; Wax, A
MLA Citation
Crow, Matthew J., et al. “Plasmonic flow cytometry by immunolabeled nanorods..” Cytometry A, vol. 79, no. 1, Jan. 2011, pp. 57–65. Pubmed, doi:10.1002/cyto.a.20994.
URI
https://scholars.duke.edu/individual/pub765197
PMID
21182183
Source
pubmed
Published In
Cytometry A
Volume
79
Published Date
Start Page
57
End Page
65
DOI
10.1002/cyto.a.20994

Loss of beta-catenin impairs the renewal of normal and CML stem cells in vivo.

A key characteristic of stem cells and cancer cells is their ability to self-renew. To test if Wnt signaling can regulate the self-renewal of both stem cells and cancer cells in the hematopoietic system, we developed mice that lack beta-catenin in their hematopoietic cells. Here we show that beta-catenin-deficient mice can form HSCs, but that these cells are deficient in long-term growth and maintenance. Moreover, beta-catenin deletion causes a profound reduction in the ability of mice to develop BCR-ABL-induced chronic myelogenous leukemia (CML), while allowing progression of acute lymphocytic leukemia (ALL). These studies demonstrate that Wnt signaling is required for the self-renewal of normal and neoplastic stem cells in the hematopoietic system.
Authors
Zhao, C; Blum, J; Chen, A; Kwon, HY; Jung, SH; Cook, JM; Lagoo, A; Reya, T
MLA Citation
Zhao, Chen, et al. “Loss of beta-catenin impairs the renewal of normal and CML stem cells in vivo..” Cancer Cell, vol. 12, no. 6, Dec. 2007, pp. 528–41. Pubmed, doi:10.1016/j.ccr.2007.11.003.
URI
https://scholars.duke.edu/individual/pub712699
PMID
18068630
Source
pubmed
Published In
Cancer Cell
Volume
12
Published Date
Start Page
528
End Page
541
DOI
10.1016/j.ccr.2007.11.003

Integration of Notch and Wnt signaling in hematopoietic stem cell maintenance.

A fundamental question in hematopoietic stem cell (HSC) biology is how self-renewal is controlled. Here we show that the molecular regulation of two critical elements of self-renewal, inhibition of differentiation and induction of proliferation, can be uncoupled, and we identify Notch signaling as a key factor in inhibiting differentiation. Using transgenic Notch reporter mice, we found that Notch signaling was active in HSCs in vivo and downregulated as HSCs differentiated. Inhibition of Notch signaling led to accelerated differentiation of HSCs in vitro and depletion of HSCs in vivo. Finally, intact Notch signaling was required for Wnt-mediated maintenance of undifferentiated HSCs but not for survival or entry into the cell cycle in vitro. These data suggest that Notch signaling has a dominant function in inhibiting differentiation and provide a model for how HSCs may integrate multiple signals to maintain the stem cell state.
Authors
Duncan, AW; Rattis, FM; DiMascio, LN; Congdon, KL; Pazianos, G; Zhao, C; Yoon, K; Cook, JM; Willert, K; Gaiano, N; Reya, T
MLA Citation
Duncan, Andrew W., et al. “Integration of Notch and Wnt signaling in hematopoietic stem cell maintenance..” Nat Immunol, vol. 6, no. 3, Mar. 2005, pp. 314–22. Pubmed, doi:10.1038/ni1164.
URI
https://scholars.duke.edu/individual/pub712703
PMID
15665828
Source
pubmed
Published In
Nature Immunology
Volume
6
Published Date
Start Page
314
End Page
322
DOI
10.1038/ni1164

Notch as a target to modulate hematopoietic stem cell differentiation

Authors
DiMascio, L; Congdon, K; Pazianos, G; Zhao, C; Cook, JM; Willert, K
MLA Citation
DiMascio, L., et al. “Notch as a target to modulate hematopoietic stem cell differentiation.” Cancer Biology and Therapy, vol. 4, no. 2, Feb. 2005.
URI
https://scholars.duke.edu/individual/pub766228
Source
scopus
Published In
Cancer Biology & Therapy
Volume
4
Published Date