PEOPLE

Al Powers
Al Powers, M.D.

Alvin C. Powers, the Joe C. Davis Chair in Biologic Science and Professor of Medicine, Molecular Physiology and Biophysics at Vanderbilt University, is the Director of the Vanderbilt Diabetes Center, the Chief of the Vanderbilt Division of Diabetes, Endocrinology, and Metabolism, and the Director of the Vanderbilt Diabetes Research and Training Center, a NIH-funded center that facilitates the diabetes-related research of more than 120 Vanderbilt scientists. He is a physician-scientist whose research on type 1 and type 2 diabetes focuses on pancreatic islet biology, development, and function. His research is or has been supported by the NIH, the VA Research Service, the JDRF, and the American Diabetes Association (ADA). Dr. Powers is also the Director of the Vanderbilt Medical Student Research Training Program in Diabetes, Endocrinology, and Metabolism and the Coordinator for the NIDDK Medical Student Research Program in Diabetes. These two programs enable more than 100 medical students to conduct diabetes-related research each summer at a NIDDK-supported Diabetes Research Center. Dr. Powers, a physician at Vanderbilt University Medical Center and the VA Tennessee Valley Healthcare System, is listed by Castle Connolly Medical Ltd as one of “America’s Top Doctors.” Dr. Powers has served on advisory panels or study sections for the NIH, the JDRF, the Endocrine Society, and the ADA and currently serves on the ADA’s national Board of Directors. In 2016, he is serving as the President-Elect, Medicine & Science of the American Diabetes Association. Dr. Powers received his undergraduate degree from the University of Virginia and his medical degree from the University of Tennessee Center for the Health Sciences. After training in internal medicine at Duke University Medical Center, Dr. Powers trained in Endocrinology and Diabetes at the Joslin Diabetes Center, the Massachusetts General Hospital, and Harvard Medical School.




Radhika Aramandla, M.S.

From Guntur, India
Radhika Aramandla, M.S.
Senior Research Specialist
Education

M.S., Vanderbilt University
B.S., Nagarjuna University, Majored in Math, Physics, & Chemistry

Radhika's research interests are the molecular aspects of type 1 and type 2 diabetes. She is involved in projects dealing with human islet transplantation to study human islet survival, function, regeneration and proliferation.

She has generated various animal models including mice that express the firefly luciferase transgene in the pancreatic islets to study beta cell survival and mass regulation by in vivo imaging. In addition to her research responsibilities, Radhika also manages the organizational needs of the lab at Vanderbilt.

Marcela Brissova, Ph.D.

From Martin, Slovakia
Marcela Brissova, Ph.D.
Research Associate Professor, Division of Diabetes, Endocrinology & Metabolism
Director, Islet Procurement and Analysis Core, Vanderbilt Diabetes Research & Training Center
Education

Ph.D., Slovak University of Technology, Bratislava, Slovakia

A faculty member since 2001, Dr. Brissova first joined Vanderbilt for postdoctoral training in the Department of Chemical and Biomolecular Engineering. Dr. Brissova’s research interests include the biology of pancreatic islets with a focus on the regulation of beta cell gene expression to provide insight into processes controlling normal pancreatic beta cell function in rodent models and translating this research to human islet biology. Her research also includes the study of molecular events involved in the development of pancreatic islet vasculature and innervation and their role in regulation of pancreatic islet function. She also directs the Islet Procurement and Analysis Core of the Vanderbilt Diabetes Research & Training Center.



Chunhua Dai, M.D.

From Hunan, China
Chunhua Dai, M.D.
Research Associate Professor
Education

M.D., Hunan Medical University
M.S., Hunan Medical University
Residency, Hunan Medical University, Internal Medicine
Fellowship, Hunan Medical University, Hematology

Dr. Dai began her career at Vanderbilt University Medical Center in the Division of Hematology/Oncology before joining the Powers Research Group in the Division of Diabetes, Endocrinology, & Metabolism. Her research focuses on the molecular, cellular, and vascular changes in human islets when they are challenged with hyperglycemia and/or insulin resistance in vivo. She is investigating in vivo age-dependent human beta cell proliferation and how current therapeutic agents for type 2 diabetes preserve and/or enhance human beta cell function or survival in vivo.

Danielle Dean, Ph.D.

From Murfreesboro, TN
Danielle Dean, Ph.D.
Postdoctoral Fellow
Education

Ph.D. in Molecular and Systems Pharmacology, Emory University
M.S. in Biochemistry, Cellular and Molecular Biology, University of Tennessee – Knoxville
B.S. in Biochemistry, Cellular and Molecular Biology, University of Tennessee – Knoxville

While at Emory University, Danielle was awarded Toxicology Scholar for her work on neurodegeneration. She now studies signals that regulate the growth of alpha cells in the pancreatic islet. Recently, she discovered that a serum factor in mice with interrupted glucagon signaling stimulates both human and mouse alpha cell proliferation and she is characterizing how alpha cells respond to this factor.

In her free time, Danielle loves to volunteer, cook, garden, homebrew, and can/pickle just about any food.



Rachana Haliyur

From Chantilly, VA
Rachana Haliyur
M.D./Ph.D. Student
Education

B.S. in Biochemistry, University of Maryland Baltimore County

Rachana's research interests include type 1 diabetes (T1D), cell growth and proliferation, and cellular responses to metabolic stress.

By implementing an integrative approach to study both the native pancreas and isolated islets from the same human donor, she and the Powers Group are working to characterize the function and morphology of T1D pancreatic islets using in vitro and in vivo functional studies, immunohistochemistry, and imaging mass spectrometry. One of her projects focuses on the glucagon-producing alpha cells in T1D islet and identifying the mechanisms behind disordered glucagon secretion in T1D.

Nathaniel Hart, Ph.D.

From Tucson, Arizona
Nathaniel Hart, Ph.D.
Postdoctoral Fellow
Education

Ph.D., Physiological Sciences, University of Arizona
B.S., Physiology, University of Arizona

After graduating from the University of Arizona, Nathaniel joined the U.S. Peace Corps as an education volunteer in biology. He taught high school biology in Mangunde, Sofala, Mozambique. During graduate training, Nathaniel’s work focused on targeting β-cells for imaging and therapy.

In the Powers’ Lab, Nathaniel’s projects include:

  1. Investigation of pancreas/islet development in the young human pancreas, focused on defining endocrine cell plasticity and establishment in humans.
  2. Dissection of a role for the Cystic Fibrosis Transmembrane Conductance Regulator in β-cells function to define the underlying causes of Cystic Fibrosis Related Diabetes.
  3. Identification of islet and pancreatic dysfunction in Type 2 diabetics integrating several methodologies to examine islet function and pancreatic tissue from the same donor.


Regina Jenkins, HT (ASCP)

From Nashville, TN
Regina Jenkins, HT (ASCP)
Histotechnologist Research
Education

HT (ASCP), American Society for Clinical Pathology, Board of Certification
A.A.S in Office Administration, Nashville State Community College

Regina has worked as a histotechnician (HT) for 25 years in both the clinical and research realms. Regina also assisted pathologists on a part-time basis as a college student which led her to decide on this career path. Regina received her HT certification from the American Society for Clinical Pathology (ASCP) in May of 2004. That same year she began working at Vanderbilt and in December 2016 she joined the Powers lab.

Jill Lindner, B.S., M.Ed.

From New York City, NY
Jill Lindner, B.S., M.Ed.
Projects Manager
Education

M. Ed. in Secondary Education, Vanderbilt University
B.S. in Biology, University of Tennessee – Knoxville

Jill joined the Division of Diabetes, Endocrinology and Metabolism in 2016, where she serves as a Projects Manager for various scientific projects within the Al Powers group.

She is a long standing Vanderbilt employee whose career spans clinical research (David Rabin Lab - Division of Endocrinology), basic research (Mark Magnuson Lab - Vanderbilt Center for Stem Cell Biology), secondary education (Science Educator - John Overton High School, Nashville, TN) and website application support (Vanderbilt Center for Stem Cell Biology).



Neil Phillips, Ph.D.

From Dundee, Scotland, UK
Neil Phillips, Ph.D.
Postdoctoral Fellow
Education

Postdoctoral Fellow in Human Gene Therapy, Stanford University, California, 2006-2012
Ph.D. in Cellular Microbiology, University of Cambridge, UK, 2001- 2006
M.S. in Medical Microbiology, University of Glasgow, UK, 1996-2001

After completing his Ph.D. in Cellular Microbiology in Cambridge, Neil switched gears and performed Postdoctoral training in human gene therapy and viral vector biology (adenovirus, adeno-associated virus and lentivirus-based systems). At Stanford, Neil had a long term interest in developing non-invasive diagnostic imaging tools for use in the clinic, and during his work at Stanford, also developed an interest in gene-based therapeutics for metabolic diseases such as type 1 diabetes. Neil moved to Vanderbilt and the Powers lab in 2012 to investigate pancreatic development and dysfunction, especially in type 1 and type 2 diabetes.

He is involved in developing new pancreatic beta-cell specific molecules such as aptamers and nanosponges for drug delivery and diagnostic purposes.

Greg Poffenberger, M.S.

From Hagerstown, Maryland
Greg Poffenberger, M.S.
Senior Research Specialist
Education

M.S. in Laboratory Investigation, Vanderbilt University
B.S. in Biochemistry, Lipscomb University

Greg has worked in the Powers Group since 2003. His areas of expertise are small animal surgeries, functional islet analysis/assays in vitro and in vivo.

Greg took a very different path in his pursuit of a career in research. He comes from a family of entrepreneurs that include businesses in office solutions and restaurants. He started working as an electrician in his hometown of Hagerstown, MD. He then moved to Nashville to manage national restaurant chains. Greg then changed career paths with Avco Corporation, a Nashville based aircraft company. He later worked at the Smyrna, TN Airport and served as a structural airframe manager.

Greg studied Biochemistry at Lipscomb University and later earned his master’s degree at Vanderbilt University. He started in research at Vanderbilt in the Infectious Disease Department and then later joined the Vanderbilt Hormone Assay & Analytical Services Core while being mentored by Wendell Nicholson in hormonal assay development.

Greg is an integral part in all human islet studies. He collaborates with other laboratories within and outside of Vanderbilt University.



Diane Saunders

From Durham, NC
Diane Saunders
MPB Graduate Student
Education

B.A. in Studio Art & B.S. in Biology, Bates College

In the Powers Lab, Diane is investigating the role of pancreatic endothelial cell populations in the islet microenvironment, by determining their role in macrophage recruitment and beta cell regeneration. She is also isolating subpopulations of human islet cells, ultimately characterizing how gene expression varies during developmental stages and in disease states.

Alena Shostak, M.S.

From Minsk, Belarus
Alena Shostak, M.S.
Laboratory Manager
Education

Postgraduate training in Immunocytochemistry, Department of Neurochemistry, Max-Planck Institute for Psychiatry
M.S. in Chemistry, Belarussian State University

Alena began her career at Vanderbilt as a research assistant in the Department of Cell and Developmental Biology. In 2002, she joined the Powers Lab and currently works with Dr. Dai on research projects involving human islet response to insulin resistance, hyperglycemia, and drugs used to treat type 2 diabetes.



Erick Spears, Ph.D.

From Denver, CO
Erick Spears, Ph.D.
Postdoctoral Fellow
Education

Ph.D. in Molecular, Cellular and Developmental Biology, University of Kansas
M.A. in Biology, University of Colorado - Denver
B.A. in Environmental, Populational and Organismic Biology, University of Colorado - Boulder

Erick's general interests include in vitro modeling of human development and disease. He studied the molecular mechanisms involved in translational regulation of APC expression in human colorecatal cancer cell lines at the University of Kansas. At Vanderbilt he has established and validated an in vitro intestinal organoid system produced by directed differentiation of human induced pluripotent stem cells down the endoderm lineage. Erick is employing similar techniques to model human endocrine pancreas development and diabetes.

Jack Walker, B.S.

From Kansas City, KS
Jack Walker, B.S.
M.D./Ph.D. Student
Education

B.S. in Chemical Engineering, Washington University in St. Louis

Jack became interested in the pancreas and pancreatic islet because of its unique role in helping control and coordinate both metabolism and digestion. He joined the Powers Lab in September 2016. Using a combination of human pancreatic tissue, isolated islets, and sorted islet cell populations Jack is characterizing the functional, morphologic, and transcriptional profiles islets from individuals with type 2 diabetes. Jack plans to become a pediatrician upon his return to medical school.