Published October 11, 2013
University at Buffalo researchers have demonstrated for the first time a broad range of protein changes in the retina of a rat model of Smith-Lemli-Opitz Syndrome (SLOS).
Their groundbreaking proteomic analysis reveals that the molecular mechanisms that cause this rare, sometimes fatal, birth defect are more complex than previously thought.
“This is the first time anyone has looked at protein changes in this disease model — and we found hundreds of them,” says senior author Steven J. Fliesler, PhD, Meyer H. Riwchun Endowed Chair Professor and vice chair and director of research in the Department of Ophthalmology.
The research has been published in Molecular and Cellular Proteomics.
A key factor to the success of this research was the use of ion current-based proteomic profiling to study protein expression in the retinas of diseased versus healthy rats.
This methodology was developed in the lab of co-corresponding author Jun Qu, PhD, associate professor of pharmaceutical sciences and assistant professor of ophthalmology.
The technique proved “superior to conventional methods,” says Fliesler, who also is a professor of biochemistry and a research health scientist at the VA Western New York Healthcare System (VAWNYHS).
Qu’s lab is a national leader in proteomic profiling — a method of studying differences in protein expression on a large scale.
The technique provides coverage for many more proteins than conventional techniques, especially for numerous membrane-associated retina proteins.
The UB team’s work has resulted in numerous advantages, including the elimination of a major source of false-positives that can occur in conventional proteomics analysis.
In addition, the technique only requires extremely small amounts of material — as little as 100 micrograms — and is objective, quantitative and highly reproducible.
The method has already been developed for a wide variety of biological specimens — from microorganisms to humans.
It could be broadly applicable, holding promise for studying more common diseases, such as diabetes, cardiovascular disease, Alzheimer’s disease and age-related macular degeneration, notes Fliesler.
The UB rat model also provides the first glimpse of how cells in the retina die, an observation contributed by co-author Matthew Behringer as an undergraduate biochemistry student.
“We found that the photoreceptor (rod and cone) cells die not through conventional programmed cell death, or apoptosis, but through some alternative, as yet unknown, mechanism,” Fliesler explains.
While the retina in this SLOS animal model degenerates, it is also not known if the human retina initially develops normally and subsequently degenerates in the course of the disease.
The UB researchers overcame major obstacles in their study of SLOS, a disease involving multiple neurosensory and cognitive abnormalities and mental and physical disabilities, including those affecting vision.
First, in studying proteins, they went beyond the existing research focus to understand the disease process in a whole new way.
Defective cholesterol biosynthesis is the initial cause of SLOS. Therefore, most prior studies of the disease have focused solely on cholesterol metabolism, Fliesler explains.
“Our results suggest that there are significant alterations in molecules other than those involved in cholesterol biosynthesis that contribute to the disease mechanism,” he says.
They also modified a rat model of the disease to extend its lifespan to at least three months.
Genetic mouse models of the disease have limited utility since they live for only one day, but their retinas — like those of rats — take about a month to mature.
The research exemplifies successful collaboration between two UB labs that are also part of the State University of New York Eye Institute, a statewide eye and vision research consortium.
This consortium brings together ophthalmology researchers from SUNY medical schools, the SUNY College of Optometry and the College of Nanoscale Science and Technology.
“Thanks to these joint efforts, we have a proteomics core module and we can promote collaborations among researchers across the SUNY Eye Institute whose work requires this kind of methodology,” explains Fliesler.
“This facilitates our ability to conduct this kind of analysis cost-effectively within SUNY, as opposed to paying another institution or private company,” he adds.
The research paper is entitled “Ion Current Based Proteomic Profiling of the Retina in a Rat Model of Smith-Lemli-Opitz Syndrome.”
Additional co-authors are Chengjian Tu (first author), Jun Li and Xiaosheng Jiang, all of the School of Pharmacy and Pharmaceutical Sciences, and Bruce A. Pfeffer and Lowell G. Sheflin from VAWNYHS.
The research was supported by grants from the National Institutes of Health, the American Heart Association, Research to Prevent Blindness, as well as a Center of Protein Therapeutics Industrial Award. VAWNYHS provided some facilities and resources.