Colin Bretz, PhD
Dr. Colin Bretz is a postdoctoral research fellow studying normal and aberrant signaling mechanisms associated with ocular disease in Dr. Hartnett’s laboratory.
Before joining the lab, he completed his doctorate in the lab of John Penn, PhD, at the Vanderbilt Eye Institute, where he focused on identifying critical and potentially therapeutic signaling targets important in the pathogenesis of ocular diseases, such as diabetic retinopathy, retinopathy of prematurity, and age-related macular degeneration.
Dr. Bretz obtained his master’s degree in Biology from Wake Forest University, where he studied stress hormone signaling using genetic dissection in a Drosophila model system. He received his bachelor’s degree in Neuroscience from Vanderbilt University.
Maria is the lab administrator. She is responsible for planning and facilitating equipment maintenance, organizing supplies and lab materials logistics, and coordinating scheduling and other tasks to ensure the lab runs smoothly.
Xiaokun Han, MD
Xiaokun Han is pursuing a master’s degree in ophthalmology at China Medical University. She earned her medical degree in 2013 from Liaoning Medical College in China.
Dr. Han joined the Hartnett laboratory as a visiting scholar. Her research focuses on exploring the signaling mechanisms for aberrant angiogenesis involved in retinopathy of prematurity and age-related macular degeneration.
Kuntz joined the Hartnett laboratory in October 2015 as an lab technician. Eric’s primary research interest is in cell signaling. He worked for two years in the Janis Weis Immunology Lab at the University of Utah, assisting with studies regarding long-term immune responses to Lyme disease.
Aaron Simmons, PhD
Dr. Simmons joined the Hartnett lab as a postdoctoral research associate in June of 2017. He is interested in cellular interactions and cell signaling events contributing to pathology in oxygen-induced retinopathies, such as retinopathy of prematurity. The focus of Aaron’s work in the lab is to explore how EPO/EPO receptor and VEGF/VEGF receptor signaling contribute to the pathophysiology in retinopathy of prematurity, specifically, the effects these signaling pathways have on developing neurons and blood vessels experiencing oxygen stresses.
Prior to joining the lab, Dr. Simmons completed his doctoral training in the lab of Dr. Peter Fuerst at the University of Idaho. His dissertation work consisted of two independent projects. His first project identified cellular interactions between retinal neurons, glia, and cells of the vasculature that are responsible for shaping developmental angiogenesis into the retina. His second project focused on the basic biology of retinal bipolar cells, where he identified molecular determinants that are necessary to regulate neuron plasticity in developing and mature neurons.
1. Li, S., Sukeena, J.M., Simmons, A.B., Hansen, E.J., Nuhn, R.E., Samuels, I.S. and Fuerst, P.G. (2015). DSCAM promotes refinement in the mouse retina through cell death and restriction of exploring dendrites. Journal of Neuroscience. 2015 Apr 8;35(14):5640-54. PMID: 25855178.
2. Simmons, A.B., Merrill, M.M., Reed J.C., Deans M.R., Edwards M.M., and Fuerst, P.G. Defective angiogenesis and intraretinal bleeding in mouse models with disrupted inner retinal lamination. Investigative Ophthalmology & Visual Science. 2016 Apr 1;57(4):1563-77. PMID: 27046121
3. Simmons, A.B., Bloomsburg S.J., Billingslea S.A., Merrill, M.M., Li, S., Thomas M.W., and Fuerst, P.G. Pou4f2 knock-in Cre mouse: A multifaceted genetic tool for vision researchers. Molecular Vision. 2016 Jun 23;22:705-17. PMID: 27390513.